The on-orbit performance of the Chandra X-Ray Observatory over its first three years of observations is reviewed. Operations are running smoothly and the scientific return continues to be exciting and outstanding.

The Chandra X-ray Observatory (CXO) has now been in orbit a little over three years. During that time, the High Resolution Camera (HRC) Science Team has been carrying out a program of science observations making use of all of the capabilities of the Observatory with particular emphasis on the capabilities of the HRC for high resolution timing, and high resolution imaging. In this review of Chandra science, we present highlights of the past three years of observations including detailed studies of the Andromeda Galaxy (M31), discovery of a pulsar in the Supernova Remnant 3C58, and studies of X-ray emission from the nearby AGN, Centaurus A.

The ACIS instrument has been operating for three years in orbit, producing high quality scientific data on a wide variety of X-ray emitting astronomical objects. Except for a brief period at the very beginning of the mission when the CCDs were exposed to the radiation environment of the Outer van Allen Belts which resulted in substantial radiation damage to the front illuminated CCDs, the instrument has operated nearly flawlessly. The following report presents a description of the instrument, the current status of the instrument calibration and a few highlights of the scientific results obtained from the Guaranteed Observer Time.

The High Energy Transmission Grating Spectrometer (HETGS) on the Chandra X-ray Observatory is a powerful tool for studying the astrophysical properties of X-ray emitting objects. Emission and absorption lines and features can probe the physical properties of stellar winds, relativistic jets, supernova remnants (SNRs), active galactic nuclei and the intergalactic medium. The capabilities of this instrument are illustrated through highlights of HETGS science, with examples including the jet structure in SS433, a Doppler velocity map of SNR E0102-72, and evidence of abundance anomalies in the microquasar GRS1915+105.

The Chandra X-ray Observatory carries two transmission gratings on-board, each of them optimized for high- and low-energy photons, respectively. Each grating can be put in the beam behind Chandra's High-Resolution Mirror Assembly (HRMA); the photons collected with the HRMA and dispersed by the gratings are then collected by one of two imaging detectors located at the focal of the telescope. The Low-Energy Transmission Grating Spectrometer, LETGS, is sensitive in the range ~2 - 170 Angstroms, and is a powerful tool to study hot plasmas in a variety of astrophysical environments, from stellar coronae to clusters of galaxies. Here we report on the status of this instrument, and we describe some of the scientific results obtained with it.

We use Chandra observations to illustrate the x-ray spectral resolution and throughput required to probe the physical processes in stellar coronae. With today's capability, we are in a strong position to quantify the physical conditiosn for a number of stellar systems. The future holds the promise of dynamical studies to test the physical processes in the corona. Diagnostic studies include measurements of electron densities in cool star atmospheres. Published measurements of electron densities from Chandra and XMM-Newton in the brightest stellar coronae disagree by more than an order of magnitude. We show that reconciling these measurements requires detailed treatment of weak satellite spectra and other line blending. While these studies provide a sobering view of electron density measurements, they also provide a strong indication of what can be learned in the future when we combine high spectral resolution with high signal-to-noise. Dynamic studies using Chandra HETG Doppler shifts are so far only reported for the most rapidly rotating cool stars. These new measurements are somewhat compromised by the presence of continuum and weak line blends, and are near the statistical limit. Nevertheless, they can provide a realistic test of the spectral synthesis such that the location(s) of coronal loops can be compared to the photospheric Doppler images. Examples of what can be learned from dynamic studies are presented.

The CCDs on the Chandra X-ray Observatory are sensitive to radiation damage, particularly from low-energy protons scattering off the telescope's mirrors onto the focal plane. In its highly elliptical orbit, Chandra passes through a spatially and temporally varying radiation environment, ranging from the radiation belts to the solar wind. Translating the Advanced CCD Imaging Spectrometer (ACIS) out of the focal position during radiation-belt passages has prevented loss of scientific utility. However, carefully managing the radiation damage during the remainder of the orbit, without unnecessarily sacrificing observing time, is essential to optimizing the scientific value of this exceptional observatory throughout its planned 10-year mission. In working toward this optimization, the Chandra team developed and applied a radiation-management strategy. This strategy includes autonomous instrument safing triggered by the on-board radiation monitor, as well as monitoring, alerts, and intervention based upon real-time space environment data from NOAA and NASA spacecraft. Furthermore, because Chandra often spends much of its orbit out of the solar wind (in the Earth's outer magnetosphere and magnetosheath), the team developed the Chandra Radiation Model to describe the complete low-energy-proton environment. Management of the radiation damage has thus far succeeded in limiting degradation of the charge-transfer inefficiency (CTI) to less than 3.5(10^-6) and 1.3(10^-6) per year for the front-illuminated and back-illuminated CCDs, respectively. This rate of degradation is acceptable for maintaining the scientific viability of all ACIS CCDs for more than ten years.

We discuss the flight calibration of the spectral response of the Advanced CCD Imaging Spectrometer (ACIS) on-board the Chandra X-ray Observatory (CXO). The spectral resolution and sensitivity of the ACIS instrument have both been evolving over the course of the mission. The spectral resolution of the frontside-illuminated (FI) CCDs changed dramatically in the first month of the mission due to radiation damage. Since that time, the spectral resolution of the FI CCDs and the Backside-illuminated (BI) CCDs have evolved gradually with time. We demonstrate the efficacy of charge-transfer inefficiency (CTI) correction algorithms which recover some of the lost performance. The detection efficiency of the ACIS instrument has been declining throughout the mission, presumably due to a layer of contamination building up on the filter and/or CCDs. We present a characterization of the energy dependence of the excess absorption and demonstrate software which models the time dependence of the absorption from energies of 0.4 keV and up. The spectral redistribution function and the detection efficiency are well-characterized at energies from 1.5 to 8.0~keV primarily due to the existence of strong lines in the ACIS calibration source in that energy range. The calibration at energies below 1.5 keV is challenging because of the lack of strong lines in the calibration source and also because of the inherent non-linear dependence with energy of the CTI and the absorption by the contamination layer. We have been using data from celestial sources with relatively simple spectra to determine the quality of the calibration below 1.5 keV. We have used observations of 1E0102.2-7219 (the brightest supernova remnant in the SMC), PKS2155-304 (a bright blazar), and the pulsar PSR~0656+14 (nearby pulsar with a soft spectrum), since the spectra of these objects have been well-characterized by the gratings on the CXO. The analysis of these observations demonstrate that the CTI correction recovers a significant fraction of the spectral resolution of the FI CCDs and the models of the time-dependent absorption result in consistent measurements of the flux at low energies for data from a BI (S3) CCD.

The observation of a bright X-ray source by the Chandra X-ray Observatory's High Energy Transmission Grating Spectrometer (HETGS) can be compromised by photon pile-up in the CCD leading to false absorption features in the observed spectrum. A method for removing the effects of pile-up in a dispersed grating spectrum is presented. The effectiveness of the technique is demonstrated through its application to the HETGS observation of 4U 1636-53, a bright X-ray binary system.

The Chandra X-ray Observatory (CXO) High Resolution Camera (HRC) is a microchannel plate (MCP) based X-ray detector with heritage from similar detectors flown on the Einstein and ROSAT missions. The HRC consists of two detectors in a common housing. Improvements from the previous instruments include: fabricating the MCP from 'low-noise' glass (glass that contains a reduced level of radioactive isotopes) and surrounding the detector housing on five sides with an active coincidence detector. Both of these improvements help to maximize the X-ray signal to background noise ratio. The on-orbit background is dominated by cosmic ray and solar-wind particles. The temporal behavior of the background has two parts: a quiescent level and a flaring component. The quiescent level slowly changes with time and is correlated with the high-energy particle flux as measured by the Electron Proton Helium Instrument (EPHIN), the CXO radiation detector. The flaring component is associated with times of elevated low-energy particle flux, primarily from the Sun. A combination of on-board vetoing and filtering during ground processing provides a substantial rejection of the non-X-ray background. This work was supported by NASA contract NAS8-39073 to the Chandra X-ray Center.

This paper presents a method for modeling the X-ray scattering from random rough surfaces. An actual rough surface is (incompletely) described by its Power Spectral Density (PSD). For a given PSD, model surfaces with the same roughness as the actual surface are constructed by preserving the PSD amplitudes and assigning a random phase to each spectral component. Rays representing the incident wave are reflected from the model surface and projected onto a flat plane, which approximates the model surface, as outgoing rays and corrected for phase delays. The projected outgoing rays are then corrected for wave densities and redistributed onto an uniform grid where the model surface is constructed. The scattering is then calculated by taking the Fast Fourier Transform (FFT) of the resulting distribution. This method is generally applicable and is not limited to small scattering angles. It provides the correct asymmetrical scattering profile for grazing incident radiation. We apply this method to the mirrors of the Chandra X-ray Observatory and show the results. We also expect this method to be useful for other X-ray telescope missions.

Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the focal plane instruments on the Chandra X-ray Observatory, suffered radiation damage from exposure to soft protons during passages through the Earth's radiation belts. The ACIS team is continuing to study the properties of the damage with an emphasis on developing techniques to mitigate charge transfer inefficiency (CTI) and spectral resolution degradation. A post-facto CTI corrector has been developed which can effectively recover much of the lost resolution. Any further improvements in performance will require knowledge of the location and amount of sacrificial charge - charge deposited along the readout path of an event which fills electron traps and changes CTI. We report on efforts by the ACIS Instrument team to characterize which charge traps cause performance degradation and the properties of the sacrificial charge seen on-orbit. We also report on attempts to correct X-ray pulseheights for the presence of sacrificial charge.

In this work we describe a simulator developed to model the x-ray response of the backside illuminated Chandra CCDs. The model is based on the Monte Carlo technique, where individual x-ray photons are thrown into the silicon structure and the behavior of the simulated electron clouds is calculated. In order to reproduce the complex redistribution function of the device at low energies we had to introduce charge losses for the clouds formed near the illuminated surface. An important feature of this model is its simulation of Charge Transfer Inefficiency (CTI) which attempts to reproduce losses of signal charge to electron traps in the buried channel of the device during different vertical and horizontal charge transfers. The CTI model takes into account a reduction of the number of empty traps in the channel due to precursor charge packets found in the previous rows of the image section of the device. Parameters of the model were tuned to fit the large amount of experimental data acquired during the on-the-ground calibration of the Chandra devices at energies ranging from 277 eV to 9.9 keV.

We present the in-flight effective area calibration of the Low Energy Transmission Grating Spectrometer (LETGS), which comprises the High Resolution Camera Spectroscopic readout (HRC-S) and the Low Energy Transmission Grating (LETG) aboard the Chandra X-ray Observatory. Previous studies of the LETGS effective area calibration have focused on specific energy regimes: 1) the low-energy calibration for which we compared observations of Sirius B and HZ 43 with pure hydrogen non-LTE white dwarf emission models; and 2) the mid-energy calibration for which we compared observations of the active galactic nuclei PKS 2155-304 and 3C 273 with simple power-law models of their seemingly featureless continua. The residuals of the model comparisons were taken to be true residuals in the HRC-S quantum efficiency (QE) model. Additional in-flight observations of celestial sources with well-understood X-ray spectra have served to verify and fine-tune the calibration. Thus, from these studies we have derived corrections to the HRC-S QE to match the predicted and observed spectra over the full practical energy range of the LETGS. Furthermore, from pre-flight laboratory flatfield data we have constructed an HRC-S quantum efficiency uniformity (QEU) model. Application of the QEU to our semi-empirical in-flight HRC-S QE has resulted in an improved HRC-S on-axis QE. Implementation of the HRC-S QEU with the on-axis QE now allows for the computation of effective area for any reasonable Chandra/LETGS pointing.

EPIC, on the Newton Observatory, comprises three CCD cameras that provide spectroscopic imaging over the band 0.1-12 keV, with full coverage of the 30' diameter field of view of the three telescopes. The combination of bandwidth, throughput, and spectral resolution, has produced many interesting observations in more than two years of operation. These range from stars, normal, and neutron, SNR & Pulsars, via galaxies, to clusters of galaxies and the most distant quasars. Some of the latest results will be presented. A few days' operation on orbit provides more instrument performance data that can be gathered in the most thorough ground calibration, and many new facets of the instrument performance become evident in orbit. The high throughput of the Newton telescopes provides images and spectra of high statistical precision. This puts an additional burden on the calibration, and there has been much progress by the EPIC team in defining a precise and accurate calibration at the few percent level. The EPIC MOS CCDs perform well in orbit and show considerable radiation hardness against soft protons, due to their peculiar architecture. The degradation of spectral resolution, due to radiation damage, is dominated by hard solar flare protons. At present, this is within the predicted limits and the good spectral performance of EPIC is maintained.

The x-ray observatory XMM-Newton is in orbit since the 10 December 1999. In the first half-year an extensive program has been carried out to commission, calibrate and verify the performance of the payload, followed by the routine phase, in which guaranteed time observations and regular guest observer programs are conducted. After a short discussion of the pn-CCD camera and its in-orbit calibration, I will present scientific results, concentrating on observations of super nova remnants, galaxies and clusters of galaxies. They demonstrate the excellent peformance of the pn-camera.

XMM-Newton was launched in December 1999 and science operations started in March 2000. Following two years of very successful operations, a report on the instrument performance and a selection of exciting new results are presented. Behind two of the three telescopes of XMM-Newton Reflection Grating Spectrometers (RGS) are placed. Each spectrometer consists of an array of reflection gratings and a set of back illuminated CCDs. They cover the wavelength band between 6 and 38 Angstromwith a resolution varying between 100 and 600 (E/DE) and a maximum effective area of 140 cm² for the two spectrometers combined. The selected wavelength band covers the K-shell transitions of C, N, O, Ne, Mg and Si as well as the L- and M-shell transitions of Fe. After a short introduction to the instrument design, the in-orbit performance is given. This includes the line spread function, the wavelength scale and the effective area including their stability during the more than 2 years of operations. Following this a number of key scientific results are briefly addressed, illustrating the power of the RGS instrument in combination with the other instruments on-board of XMM-Newton as well as the wealth of information which is obtained as the RGS instruments operate continuously.

In this paper, a review is given of methods useful for XMM EPIC data analysis of extended sources, along with some applications to a bright massive cluster of galaxies at z=0.2, ABELL 209. This may constitute an introduction to that kind of advanced analysis, complementing cookbooks that can be found over the internet, the XMM EPIC calibration status document, and the data analysis workshops organised in VILSPA, which were only dedicated so far to point sources analysis. In addition, new spectro-imaging techniques are proposed, in order to measure for instance the intracluster medium mass and temperature profiles, or even maps.

Recent X-ray observations of active galaxies and quasars have significantly improved our ability to probe the environments of supermassive black holes. The high throughput and excellent spectral capabilities of the new generation of X-ray observatories have already revealed many new and unexpected observational results, resulting in a more precise understanding of the physics operating within a few Schwarzschild radii around the supermassive black hole, the molecular torus zone as well as the nuclear starburst activity. The talk will review the new observational results on the iron K line as an important diagnostic tool for probing matter within a few Schwarzschild radii.

The XMM-Newton observatory has the largest collecting area flown so far for an X-ray imaging system, resulting in a very high sensitivity over a broad spectral range. In order to exploit fully these performances, an accurate calibration of the XMM-Newton instruments is required. This calibration is being continuously updated, in order to refine the stable calibration parameters as well as to account for the detector response changes induced by radiation damage. We report here on the current overall status of the EPIC/MOS cameras calibrations, and in particular on the recent work involving Charge Transfer Inefficiency evolution and recovery.

The pn-CCD is the focal plane detector of one of the three X-ray telescopes aboard the XMM-Newton observatory. During revolution #156 more than 30 individual bright pixels lightened up out of approximately 150,000 pixels of the 6 cm × 6 cm large detector area. The amount of leakage current generated in the pixels cannot be explained by single heavy ions impact, however. We suggest that a micrometeoroid scattered off the mirror surface under grazing incidence reached the focal plane detector and produced the bright pixels. This proposal was studied by us experimentally at the Heidelberg dust accelerator. Micron-sized iron particles were accelerated to speeds of the order of 5 km/s impinging on the surface of an X-ray mirror under grazing incidence. Scatter products have been found with detectors placed behind the mirror. They have been analyzed by various methods to characterize their properties and the effects produced by them in the pn-CCD. Micrometeoroid damage to semiconductor detectors in the focus of grazing incidence optics might be of concern for future space projects with very large collecting area and are proposed to be studied in detail.

We describe in-orbit measurements of the mirror vignetting in the XMM-Newton Observatory, using observations of SNR G21.5-09 with the EPIC imaging cameras. The instrument features that complicate these measurements are briefly described. We show the spatial and energy dependences of measured vignetting, outlining assumptions made in deriving the eventual agreement between theory and measurement. Alternate methods to confirm these are described. We briefly describe an analysis of the stray-light rejection of the telescope.

We are conducting a measurement program on back-up filters of the XMM-Newton EPIC camera aimed at monitoring possible aging effects during the mission lifetime. One thin and one medium EPIC back-up filters have been stored since 1997 in an environment similar to that one of the flight filters (dry nitrogen box before launch, high vacuum after launch). The transmission of the two filters has been measured periodically in the 1900-10000 angstrom wavelength range where effects of aging would be clearly evident. The preliminary results, after 5 years of monitoring, show that a slight aging effect has occurred on both filters which, however, has no significant impact onto the EPIC calibration for the correct analysis of the X-ray astrophysical observations.

We have analysed the tracks left by cosmic-ray particles on the CCDs of the EPIC-MOS cameras onboard XMM-Newton. These tracks could be entirely visualized by using a special operation test mode, and their characterization could be performed. This has allowed to measure the cosmic-ray flux at the level of the focal plane, as well as the fraction of the CCD surface which is sterilized by the cosmic-ray impacts. The relation between this fraction and parameters transmitted to the ground during normal observations has been established.

The observation of comet C/2000 WM1 (LINEAR) with XMM-Newton is a highlight in the field of cometary research. During 17 hours of almost uninterrupted observations, more than one million photons were recorded with unprecedented spectral resolution. The results obtained so far clearly demonstrate that the X-ray emission is caused by charge exchange reactions between highly charged heavy ions in the solar wind - mainly oxygen and carbon - and cometary gas. Due to the high number of detected photons, an investigation of the X-ray morphology is also possible in considerable detail. The observation was also a highlight from the technological point of view, demonstrating that XMM-Newton has more capabilities than are currently utilized. In order to follow the comet, the orientation of the satellite had to be adjusted several times. This was done by just changing the guide star offsets, leaving the X-ray instruments switched on. Compared to the usual procedure with regular slews, where the X-ray instruments are reinitialized afterwards, this new technique increased the time available for scientific observations by 34% for MOS and by 83% for PN. The capability of performing quick attitude adjustments during an observation may be of interest also for other astrophysical applications.

Astro-E2 will be the fifth in a series of Japanese X-ray astronomy satellites, following Hakucho, Tenma, Ginga and ASCA. This mission is a re-challenge of the Astro-E mission, which the Institute of Space and Astronautical Science (ISAS) failed to place on a stable orbit on February 10, 2000, and the Astro-E2 satellite will be basically identical to the Astro-E satellite. It will be an international X-ray astronomy observatory characterized by the superior energy resolution of the X-ray micro-calorimeter (XRS) placed at the focal plane of the X-ray telescope (XRT) and by the wide band spectroscopy with the CCD cameras (XIS) + XRTs system and the hard X-ray detector (HXD). It is now being developed in an extensive collaboration between scientists from Japan and the United States.

The Constellation-X mission is a large collecting area X-ray facility, emphasizing observations at high spectral resolution (R ~ 300--3000) while covering a broad energy band (0.25-60 keV). By increasing the telescope aperture and utilizing efficient spectrometers the mission will achieve a factor of 25-100 increased sensitivity over current high resolution X-ray spectroscopy missions. Constellation-X is the X-ray astronomy equivalent of large ground-based optical telescopes such as the Keck and the VLT, complementing the high spatial resolution capabilities of Chandra. Key technologies under development for the mission include lightweight high throughput X-ray optics, multilayer coatings to enhance the hard X-ray performance of X-ray optics, micro-calorimeter spectrometer arrays, low power and low weight CCD arrays, lightweight gratings and hard X-ray detectors. Constellation-X will for the first time make high resolution X-ray spectroscopy of faint X-ray source populations a matter of routine. With its increased capabilities, Constellation-X will address many fundamental astrophysics questions such as observing the formation and evolution of clusters of galaxies, constraining the Baryon content of the Universe, observing the effects of strong gravity close to the event horizon of black holes and using these effects to determine the black hole rotation. The Constellation-X mission has received strong endorsements in two recent National Academy of Sciences reports: the Astronomy and Astrophysics Survey and the Committee on the Physics of the Universe.

XEUS is under study by ESA as part of the Horizon 2000+ program to utilize the International Space Station (ISS) for astronomical applications. XEUS will be a long-term x-ray observatory with an initial mirror area of 6 m² at 1 keV that will be expanded to 30 m² following a visit to the ISS. The 1 keV spatial resolution is expected to be 2-5" half-energy-width. XEUS will consist of separate detector and mirror spacecraft aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting sensitivity will then be 4×10^-18 erg cm^-2s^-1, around 200 times better than XMM-Newton, allowing XEUS to study the properties of the hot baryons and dark matter at high redshift.

The Max-Planck-Institut fuer extraterrestrische Physik (MPE), the Astrophysikalisches Institut Potsdam (AIP) and the Institute fuer Astronomie und Astrophysik der Universitat Tubingen (IAAT), together with European cooperation partners, have proposed to install an x-ray telescope on the International Space Station (ISS). The mission ROSITA will perform the first imaging all-sky survey in the medium energy x-ray range up to 10 keV with an unprecedented spectral and angular resolution. The main scientific goals are (1) to detect systematically all obscured accreting Black Holes in nearby galaxies and many new, distant active galactic nuclei, (2) to detect the hot intergalactic medium of several ten thousand galaxy clusters and groups and hot gas in filaments between clusters to map out the large scale structure in the Universe and to find in particular the rare massive distant clusters of galaxies for the study of cosmic structure evolution and (3) to study in detail the physics of galactic x-ray source populations, like pre-main sequence stars, supernova remnants, and x-ray binaries. In the hard x-ray band the ROSITA survey in this band, which was performed about 25 years ago. In the soft band the ROSITA survey will have a hundred times higher sensitivity and a hundred times better angular resolution than the last all-sky in this band, which was perforemd about 25 years ago. In the soft band the ROSITA survey will be more sensitive and have a substantially better energy and also angular resolution than the ROSAT all-sky survey. The telescope will consist of the seven 27-fold nested Wolter-1 mirror systems, the type already flown on ABRIXAS, and an ovel detector system currently being develoepd by MPE on the basis of the successful XMM pn-CCD technoloyg - a potential prototype for the planned ESA mission XEUS. Major improvements of the new camera are a higher time and energy resolution and significantly reduced ghost images. Within an industry study, recently completed, the general feasibility of such an astronomical survey telescope mounted on the ISS was established.

One of the major fields to be explored in the 21st century is the hard X-ray sky up to 50 keV or 100 keV. Above 10 keV, thermal components start to decay rapidly and then non-thermal power law continua become dominant. For example, some of SNR and Cluster of Galaxies exhibit substantial non-thermal components, which suggest high energy electrons. We would like to investigate acceleration mechanisms of such high energy particles by observing hard X-ray images and their spectra. In order to perform imaging observations in hard X-ray range up to 50 keV, supermirror hard X-ray telescopes are most promising. We have studied to put Pt/C supermirror on the mirror shells of a high throughput X-ray telescope. The first satellite mission proposed with the supermirror hard X-ray telescope is our New X-ray Telescope mission (NeXT) in Japan to be launched 2010. 6-7 supermirror telescopes will be installed at the top of an extensible optical bench. The hybrid X-ray imager will be placed on the focal plane to observe hard X-ray images up to 50 keV with CdTe pixel detector underneath a thin CCD for soft X-ray imaging. For high resolution spectroscopy, TES type calorimeters are considered without cryogen. Non-imaging hard X-ray and soft gamma ray detector is studied to achieve unprecedented sensitivity between 50 and 300 keV. NeXT will be a sort of pathfinder of hard X-ray astronomy not only technically but also scientifically.

The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed very large area coded aperture telescope array, incorporting 8m² of pixelated Cd-Zn-Te (CZT) detectors, to conduct a full-sky imaging and temporal hard x-ray survey each 95min orbit. With a sensitivity of ~0.05mCrab, it will extend the ROSAT soft x-ray and proposed ROSITA medium x-ray surveys into the hard x-ray band and enable identifiaiton and study of sources ~10-20X fainter than with the ~15-100keV survey planned for the upcoming Swift mission. At ~100-600keV, the ~1mCrab sensitivity is 300X that achieved in the only previous all-sky survey. EXIST will address a broad range of key science objectives: from obscured AGN and surveys for black holes on all scales, which constrain the acretion history of the universe, to the highest sensitivity and resolution studies of gamma-ray bursts it will conduct as the Next Generation Gamma-Ray Burst mission. We summarize the science objectives and mission drivers, and the results of a mission design study for implementation as a free flyer mission, with Delta IV launch. Key issues affecting the telescope and detector design are discussed, and a summary of some of the current design concepts being studied in support of EXIST is presented for the wide-field but high resolutoin coded aperture imaging and very large area array of imaging CZT detectors. Overall mission design is summarized, and technology development needs and a development program are outlined which would enable the launch of EXIST by the end of the decade, as recommended by the NAS/NRC Decadal Survey.

The High-Resolution Spectroscopic Imaging Mission is designed to be the first instrument to make true images of the hard X-ray/soft gamma-ray (2 - 600 keV) sky. By focusing energetic X-rays and low-energy gamma-rays, HSI will observe the cosmos with an unprecedented combination of sensitivity, spectral resolution, and angular resolving power. HSI is based on an array of multilayer grazing-incidence optics focusing onto high-resolution solid-state germanium pixel detectors with a focal length of 30-50 m. This paper describes the primary scientific objectives, technical approach to the instrumentation, and mission design.

The MAXIM Pathfinder (MP) mission is under study as a scientific and technical stepping stone for the full MAXIM X-ray interferometry mission. While full MAXIM will resolve the event horizons of black holes with 0.1 microarcsecond imaging, MP will address scientific and technical issues as a 100 microarcsecond imager with some capabilities to resolve microarcsecond structure. We will present the primary science goals of MP. These include resolving stellar coronae, distinguishing between jets and accretion disks in AGN. This paper will also present the baseline design of MP. We will overview the challenging technical requirements and solutions for formation flying, target acquisition, and metrology.

We describe the hard x-ray mission MIRAX - jointly proposed by teams from Brazil, the USA, Germany and the Netherlands. The scientific objective is to provide continuous 2-200 keV imaging of the central 1000 square degrees of our Galaxy for 9 months per year over up to 5 years. Durign times when the sun crosses the Galactic Center other areas like the Cygnus-, Vela- and the Magellanic Cloud-regions can be observed. MIRAX will detect, localize, identify and study sources of medium to hard x-ray emission, with special emphasis on short-lived, rare and unpredictable events, including weak x-ray transients and fast x-ray movae. MIRAX will reach in a one day observation a sensitivity of 1mCrab in 2-10 keV and 2.5mCrab in 10-100keV. MIRAX will provide a unique capability to study compact galactic objects - notably accreting neutron stars and black holes. It will:- Probe neutron star and x-ray burst theory wiht 20,000 type I x-ray bursts and 50 'superbursts' - Measure spin frequencies of neutron stars from 10-100 burst oscillations - Observe explosive flares and x-ray light curves during ejections in superluminal jets - Study soft gamma-ray repeaters, fast x-ray novae and new types of phenomena yet to be discovered. We describe the science and the instrumentation.

We present a mission concept for high resolution X-ray spectroscopy with a resolving power, R ~6000. This resolution is physics-driven, since it allows the thermal widths of coronal X-ray lines to be measured, and astrophysics-driven, since 50km/s resolves internal galaxy motions, and galaxy motions within larger structures. Such a mission could be small and have a rapid response allowing us to 'X-ray the Universe' using the afterglows of Gamma-ray Bursts (GRBs) as strong background sources of X-rays, and so illuminate the `Cosmic Web'. The Cosmic Web is predicted to contain most of the normal matter (baryons) in the nearby Universe.

The Baryonic Extragalactic Structure Tracer (BEST) is a SMEX-class mission that is designed to map the hot million-degree diffuse intergalactic and interstellar gas with high spectral resolution. It consists of an imaging X-ray spectrometer that can, over a 1-2 year mission, map the entire sky and conduct deep pointed observations of selected regions to profoundly extend our understanding of hot matter in the Universe. BEST will be able to detect and characterize the missing baryons in the current epoch, which are primarily in moderately overdense intergalactic regions and are predicted to account for 10 - 20% of the soft X-ray background, and also determine the properties of the hot Galactic halo and the hot Galactic gas, crucial to understanding the evolution and dynamics of our Galaxy and its interstellar medium.

The x-ray Evolving Universe Spectroscopy mission (XEUS) is an ambitious project under study by the European Space Agency (ESA), which aims to probe the distant hot universe with comparable sensitivity to NGST and ALMA. The effective optical area and angular resolution required to perform this task is 30m² and <5" respectively at 1 keV. The single Wolter-I x-ray telescope having these characteristics will be equipped with large area semiconductor detectors and high-resolution cryogenic imaging spectrometers with 2 eV resolution at 1 keV. A novel approach to mission design has been developed, placing the detector instruments on one dedicated spacecraft and the optics on another. The International Space Station (ISS) with the best ever available infrastructure in space will be used to expand the mirror diameter from 4.5 m to 10 m, using robotics and extravehicular activities. The detector spacecraft (DSC) uses solar-electric propulsion to maintain its position while flying in formation with the mirror spacecraft. The detector instruments are protected from straylight and contamination by sophisticated baffles and filters, and employ the earth as a sun shield to make the most sensitive low energy x-ray observations of the heavily red-shifted universe. Detailed approaches, including alternatives to the baseline mission design of XEUS, have been and continue to be addressed, ensuring an efficient concept to be available for the eventual mission implementation. Both the development of the XEUS baseline scenario and complementary work conducted on some alternative mission designs are discussed.

Strategy of formation flying for the X-ray Evolving Universe Spectroscopy mission (XUES) is discussed, in which an X-ray telescope of 10 m diameter and 50 m focal length will be constructed in orbit by formation flying the X-ray mirror and the focal plane X-ray detectors on two separate spacecrafts. We first studied the thrust force required to keep the detector spacecraft (DSC) in the non-Keplerian orbit. We find the direction of the thrust vector rotates twice per a single spacecraft orbital evolution along a circle parallel to the orbital plane. The absolute value of thrust needs to be varied by a factor of two or less. The maximum thrust force required is 0.47 N assuming a 600 km altitude and a 4000 kg DSC mass. The present baseline design requires no moving mechanism, instead requires a large amount of propellant because of relatively low thruster efficiency. The spacecraft is estimated to weigh about 6000 kg. We studied an alternative design in which the thruster efficiency is optimized and showed that the spacecraft mass can be reduced to 4000 kg. This, however, requires a rotation mechanism and additional constraints on the spacecraft operation.

We describe a proposal for an added capability of fast timing to the European x-ray astronomy mission XEUS. The scientific value of fast timing observations for the investigation of compact objects is recognized and has been demonstrated through observations by the Rossi x-ray Timing Explorer. We propose to make use of the huge collecting area of XEUS for timing studies with unparalleled photon statistics and time resolution. We describe the sceintifc motivation, e.g. to probe strong gravity fields around collapsed objects and to constrain the equation of state of dense matter in neutron stars. We discuss options for the implementation of detectors which coudl be small silicon drift detectors out of focus.

In the Science Payload Technology Division of the European Space Agency X-ray optics are being developed for space based astrophysics observatories and planetary missions. Due to the gazing incidence geometries required in the x-ray regions of interest, and the high angular resolutions required, the mass of the optics becomes a major driver in mission design. New technologies have to be explored for future applications, simultaneously achieving good angular resolution and low mass while maintaining collecting aperture. The cosmology mission XEUS requires very large effective area, 30m² at 1keV, x-ray optics with high angular resolution of below 5" with a goal of 2". This implies a large aperture for a single telescope system, which will necessarily require assembly or deployment in space, and which will be formed by basic mirror modules known as petals. The petals must remain compatible with compact ground handling and production tools and will require minimum modifications to existing calibration facilities. The technology for the implementation of this Wolter-I design is currently based on the European heritage of x-ray optics development and production, dating back to Exosat, launched in 1983, to the currently operating XMM-Newton observatory. Substantial further research and development is required, however, with the key aspects therefore being low mass design and industrialization of the production. New approaches are being considered in parallel to evolutions of the current state-of-the-art technologies. In addition to the XEUS mission optics options, extremely low mass Wolter-I optics are being developed for applications in very deep orbits or planetary remote sensing, having even stronger mass constraints, but having a more relaxed angular resolution requirement. Such optics systems feature dramatically reduced mirror thickness and therefore mass. The current state of development of the ultra-lightweight x-ray optics systems will be presented together with future development plans.

We provide an overview of the Constellation-X SXT development program. We describe the performance requirements and goals, and the status of the technology development program. The SXT has a 1.6-meter diameter, a 10-meter focal length, and is to have an angular resolution exceeding 15 arc seconds. It has a modular design, incorporting lightweight, multiply nested, segmented Wolter Type I x-ray mirrors. All aspects of the design lend themselves to mass-production. The reflecting surfaces are produced by epoxy replication off precision mandrels onto glass substrates that have been accurately formed by thermal slumping. Coalignment of groups of relfectors to the required sub-micron accuracy is assisted by precison silicon micorstructures. Optical alignment is performed using the Centroid Detector Assembly originally developed for aligning the Chandra mirror. Recent efforts have concentrated on the producotin of an Engineering Unit, incorporating the components for the first time into a flight-like configuration. We summarize the status of the development of the processes for the key components and the initial metrology results of the Engineering Unit.

We describe a new technical approach for observations of Galactic and extra-Galactic soft X-ray sources with ultra-high angular resolution. The technique is based on the use of recently developed diffraction-limited, normal-incidence mirror substrates and ultra-short-period multilayer coatings, tuned to specific bright emission lines in the range 16 < l < 40 Å, for the construction of a diffraction-limited X-ray telescope. Sub-milliarcsecond resolution could be achieved in a moderately-sized Cassegrain or prime-focus geometry, while resolution of order 0.01 microarcseconds could be achieved using a synthetic aperture X-ray interferometer constructed from an array of such telescopes spread over a 50 km baseline. We describe our technical approach in detail and outline some of the observations that would become possible with the proposed instrumentation.

The X-Ray telescopes (XRT) for the US/Japan collaborative mission Astro-E2 will be of the same basic design as those built for the original Astro-E mission which failed to reach orbit in Feb. 2000. The NASA/GSFC X-ray Astrophysics Branch will again provide the five lightweight, broad-band mirrors for the mission. X-ray calibrations of the mirrors delivered for the original Astro-E instrument showed spatial resolutions characterized by Half-Power Diameters (HPD) in the range of 1.8 - 2.2 minutes of arc, essentially independent of photon energy in the soft x-ray band. For the mission Astro-E2, both funding constraints and management decisions drastically limit any design modifications, so reflector fabrication and assembly procedures have remained largely unchanged. Nevertheless, in view of the importance in scientific return of attaining even a modest improvement in the spatial resolution of these mirrors, we have carefully considered the various sources of spatial error and, whenever possible, incorporated promising modifications. In this paper, we discuss our current understanding of the various error components as well as the small changes we have been able to implement.

X-ray telescopes (XRTs) of nested thin foil mirrors were developed for Astro-E, the fifth Japanese x-ray astronomy satellite. Although the launch was not successful, the re-flight of Astro-E mission is approved as Astro-E2 and will carry the same XRTs. Ground-based calibration of Astro-E XRT revealed that its image quality and effective area are somewhat worse than what are expected from the original design. Conceivable causes of these defects of the XRT performance (i.e., surface roughness, waviness, misalignment of reflectors, and so on) are examined by X-rays and optical microscopic measurements. In this paper, we distinguish quantitatively these causes to limit the performance of the Astro-E XRT. Using the detail measurements, we can attribute both degradation of the image quality and a deficit of the effective area from the design values mainly to a slope error with a mm scale in each reflector and shadowing effects of neighboring reflectors due to various factors. There is still room for improvement in the support system of reflectors (i.e., alignment bars) in the XRT. One of the main aims of the mirror system calibration is to construct response function. Therefore, it is important that the development of a representative numerical model and its validation against extensive ground-based calibration. Taking account of the results of the pre-flight calibration and the microscopic measurements, we develop and tune a ray-tracing simulator which constructs the XRT response function for a point source at an arbitrary off-axis angle and spatial distributions of celestial X-ray sources.

XEUS is a single focus Wolter type I telescope with aperture diameter 10 m and focal length 50 m providing a collecting area >20 m^2 at 1 keV with angular resolution 2-5 arc seconds. The aperture is divided into sectors and the Wolter surfaces are manufactured as sector plates rather than continuous surfaces of revolution. The major technological challenges in constructing the mirror system are (i) manufacture of very high quality mirror plates (ii) handling and fixing of the plates during integration into a sector module and (iii) metrology of the reflecting surfaces before and during integration to ensure the desired angular resolution is met. This paper discusses techniques that can satisfy challenge (iii). A metrology scheme which can be used for monitoring the figure of the mirror plates during production, handling and integration is proposed. Simulation of the system demonstrates that the scheme has the potential for sub arc second accuracy which is more than adequate to satisfy the requirements for XEUS.

We present new results from a program to develop large area X-ray telescopes that are made from thin plastic shells. We use multi-shell cylindrical lenses in a point-to-point configuration to form full aperture images of the small focal spot in a an X-ray tube on a microchannel plate detector. The image data are analyzed to yield radial profiles and encircled energy curves. The derived parameters can be extrapolated to the case of a telescope that is a conical approximation to Wolter 1 optics. The plastic shells can be coated with suitable mono- or multilayers that allow for a wideband coverage of X-ray energies. Our current program is focused on the development of a large area, hard X-ray telescope for a balloon payload.

The Constellation-X mission is a follow-on to the current Chandra and XMM missions. It will place in orbit an array of four identical X-ray telescopes that will work in unison, having a substantial increase in effective area, energy resolution, and energy bandpass over current missions. To accomplish these ambitious increases new optics technologies must be exploited. The primary instrument for the mission is the Spectroscopy X-Ray Telescope (SXT), which covers the 0.2 to 10 keV band with a combination of two x-ray detectors: a reflection grating spectrometer (RGS) with CCD readout, and a micro-calorimeter. Mission requirements are an effective area of 15,000 cm² near 1.25 keV, 6,000 cm² near 6 keV, and a 15 arcsec (HPD) resolution requirement with a goal of 5 arcsec. The Constellation-X SXT uses a segmented design with lightweight replicated optics. A technology development program is being pursued with the intent of demonstrating technical readiness prior to the program new start. Key elements of the program include the replication of the optical elements, assembly and alignment of the optics into a complete mirror assembly and demonstration of production techniques needed for fabrication of multiple units. In this paper we present the development of SXT assembly and alignment techniques and describe recent work and current status on the first of these assemblies, the Optical Assembly Pathfinder, in which precision mechanical techniques and optical metrology are used to assemble and align the flexible optical elements.

As NASA's next major x-ray observatory, Constellation-X will have a photon collection area of 30,000 cm² at 1 keV, which, after folding other instrumental respojnses, translates into an effective aera of 15,000 cm². The observatory consists of four identical satellites each of which carries a spectroscopic x-ray telescope mirror assembly (SXT) that is 1.6 m in diameter and has a focal length of 10 m and a collection area of 7,500 cm² at 1 keV and an angular resolution of 15" HPD at the system level. Each mirror assembly consists of a large number of mirror segments precisely assembled together. Our development of the mirror segments is divided into two steps. The first one is to develop the basic approach and fabricate segments within the constraints of existing infra-structure to meet the angular resolution requirement, but not mirror segments precisely assembled together. Our development of the mirror segments is divided into two steps. The first one is to develop the basic approach and fabricate segments within the constraints of existing infra-structure to meet the angular resolution requirement, but not mirror segment size requirement. We have all but successfully competed this part of the development. We are now on the verge of going into the second step, that is to fabricate mirror segments of larger sizes to reduce the number of segments that have to be aligned and integrated. In this paper, we report on the requirements and the development status of the mirror segments. These assembly and other requirements of the SXT are reported elsewhere.

We report recent work on segmented glass optics for the Constellation-H hard x-ray telescope. This effort seeks to both improve the figure of the free-standing glass substrates, and to refine a newly-developed mounting technology for the substrates. We discuss metrology on recently characterized glass shells both unmounted and mounted. We also present plans for several prototype optics to be constructed in the upcoming year.

The NASA's Constellation X-Ray Mission consists of a Soft X-Ray Telescope (SXT) based on large collecting area optics plus a focusing Hard X-Ray Telescope (HXT) operating between 8 and 70 keV and possibly at even higher energy. The Con-X HXT will have a focal length of 10 m and graze angles are small (0.25 - 0.1 deg). The substrates will be coated with multilayers to enhance the reflectivity but single heavy element coatings are an alternative for the small diameter substrates of the set. Twelve copies of the HXT are distributed evenly among the four Con-X spacecrafts. With multiple telescopes it is appropriate to consider electroforming, the replication process used successfully by Beppo-SAX, JET-X/SWIFT, and XMM-Newton, to produce their substrates. The important feature of the technique is that for mirrors with aperture diameters less than 40 cm also with thin substrates it is possible to achieve good angular resolution, which is important for obtaining high signal-to-noise ratios in deep observations and imaging extended sources. We review the main results of our development study devoted to proving the feasibility of the process for the Con-X/HXT, with particular stress on demonstrating, not only by theoretical considerations but also presenting an important experimental proof, that we can satisfy the severe mass constraints of the mission still maintaining good imaging capabilities.

We describe and discuss the LOBSTER EYE X-ray telescope project including recent results of the development and tests of advanced telescope prototypes. They include both very small (3 × 3 mm) as well as large (300 × 300 mm) Schmidt lenses. Considerations for a space experiment on a small scientific satellite of a Nadezhda type are also discussed.

The proposed Reflection Grating Spectrometer (RGS) on the Constellation-X mission is designed to provide high-resolution x-ray spectroscopy of astrophysical sources. Two types of reflection grating geometries have been proposed for the RGS. In-plane gratings have relatively low-density rulings (~500 lines/mm) with lines perpendicular to the plane of incidence, thus dispersing x-rays into the plane. This geometry is similar to the reflection grating spectrometer flown on the X-ray Multi-Mirror (XMM) mission. Off-plane, or conical, gratings require much higher density rulings (>5000 lines/mm) with lines parallel to the plane of incidence, thus dispersing x-rays perpendicular to the plane. Both types present unique challenges and advantages and are under intensive development. In both cases, however, grating flatness and assembly tolerances are driven by the mission's high spectral resolution goals and the relatively poor resolution of the Wolter foil optics of the Spectroscopy X-ray Telescope (SXT) that is used in conjunction with the RGS. In general, to achieve high spectral resolution, both geometries require lightweight grating substrates with arcsecond flatness and assembly tolerances. This implies sub-micron accuracy and precision which go well beyond that achieved with previous foil optic systems. Here we present a progress report of technology development for the precision shaping, assembly and metrology of the thin, flat grating substrates.

A reflection grating spectrometer featuring off-plane, radial groove gratings for the Constellation-X mission will be presented. Preliminary work shows that off-plane designs can significantly enhance the scientific capabilities of the mission baseline design. Resolutions up to λ/Δλ~5000 can be achieved. The design accomplishes the mission goal for throughput and may also significantly reduce the assembly tolerances. Detailed raytracing and performance assessment of a strawman configuration are included.

The MAXIM (Mico-Arcsecond X-Ray Imaging Mission) and MAXIM Pathfinder, a technology precursor mission, is considered by NASA as 'visionary missions' in space astronomy. Currently the MAXIM mission design would fly multiple spacecraft in formation, each carrying precision optics, to direct x-rays from an astronomical source to collector and imaging spacecrafts. The mission architecture is complex and provides technical challenges in formaiton flying and external metrology, and target acquisition. To further develop the concept, an integrated model (IM) of the MAXIM and MAXIM Pathfinder was developed. Individual subsystem models from disciplines in structural dynamics, optics, controls, signal processing, detector physics and disturbance modelign are seamlessly integrated into one cohesive model to efficiently support system level trades and analysis. The optical system design is a unique combination of optical concepts and therefore results from the IM were extensively compared with ASAP optical software.

MAXIM consists of thirty-two individual grazing incidence interferometer channels that act, in combination, like a high-resolution imaging telescope. In this paper, we will describe an optical design for Maxim and calculate principal optical tolerances. These tolerances offer advantages that make anticipated engineering challenges more soluble and affordable within the limitations of current technology. We also discuss key design tradeoffs that contribute to a preliminary tolerance budget.

The high rate at which importatn results are emanating formthe Chandra X-ray Observatory heightens our appreciation of the significance of high angular resolution telescopes in x-ray astronomy. However, the Chandra telescope is probably the last member of a line of high resolution telescopes with a conventional architecture. Qualitative improvement upon Chandra's resolution requires a new technology. We discuss a promising approach that is capable potentially of achieving microarcsecond resolution, possibly the highest angular resolution in astronomy of any wavelength band. It is based upon x-ray optics that focus by transmission at normal incidence rather than by reflection at grazing incidence. Its components are refractive lenses and Fresnel zone plantes. Extreme chromatic aberration is intrinsic to these devices but it can be overcome in small wavelength intervals above 2 keV with a technique described by Van Speybroech and by other methods. Like x-ray interferometry these systems have extremely long focal lengths and require 'formation flying' consisting of precise positioning between the optics and detector that be aboard separate spacecraft spaced far apart. However, it is less demanding of accuracy in formation flying than x-ray interferometery. These systems have much lower mass than grazing incidence telescopes with comparable collecting area.

The High Energy Focusing Telescope (HEFT) will observe a wide range of objects including young supernova remnants, active galactic nuclei, and galaxy clusters at energies between 20 and 70 keV. Large collecting areas are achieved by tightly nesting layers of grazing incidence mirrors in a conic approximation Wolter-I design. The segmented mirrors that form these layers are made of thermally formed glass substrates coated with depth-graded multilayer films for enhanced reflectivity. The mirrors are assembled using an over-constraint method that forces the overall shape of the nominally cylindrical substrates to the appropriate conic form. We will present performance data on the HEFT optics and report the current status of the assembly production.

The development of hard X-ray focusing optics is widely recognized as one of key technologies for future X-ray observatory missions such as NeXT(Japan), Constellation-X(US) and possibly XEUS(Europe). We have developed hard X-ray telescope employing depth-graded multilayers, so-called supermirrors. Its benefit is to reflect hard X-rays by Bragg reflection at incidence angles larger than the critical angle of total external reflection. We are now continuously fabricating platinum-carbon(Pt/C) supermirror reflectors for hard X-ray observations. In this paper we focus on our development of the hard X-ray telescope for the first balloon flight observation (InFOCuS) and its results. InFOCuS is an international balloon-borne hard X-ray observation experiment initiated by NASA/GSFC. InFOCuS hard X-ray telescope have been jointly developed by Nagoya University and GSFC. The telescope is conical approximation of Wolter-I optics with 8m focal length and 40cm diameter. It consists of 255 nested ultra-thin reflector pairs with incidence angles of 0.10 to 0.36deg. Reflectors are coated with Pt/C supermirrors with periodic length of 2.9 to 10nm and bi-layer number of 25 to 60, depending on incidence angles. The effective area and imaging quality are expected as 100 cm² at 30 keV and 2 arcmin in half power diameter, respectively. The InFOCuS experiment was launched on July 5, 2001, from National Scientific Balloon Facility in Texas, USA. We successfully observed Cyg X-1, chosen for a calibration target, in 20-40keV energy band. We are planning to carry out next flight for scientific observations as soon as additional telescopes, detectors, and upgraded gondola system are implemented.

We are fabricating optics for the hard-x-ray region using electroform nickel replication. The attraction of this process, which has been widely used elsewhere, is that the resulting full shell optics are inherently stable and thus can have very good angular resolution. The challenge with this process is to develop lightweight optics, and to keep down the costs of mandrel fabrication. We accomplished the former through the development of high-strength, low-stress nickel alloys that permit very thin, stable, shells without fabrication- and handling-induced deformations. For the latter, we have utilized inexpensive grinding and diamond turning to figure the mandrels and then purpose-built polishing machines to finish the surface. In-house plating tanks and a simple water-bath separation system complete the process. To date we have built shells ranging in size from 5 cm diameter to 50 cm, and with thickness down to 100 micron. For our HERO balloon program, we are fabricating over 200 iridium-coated shells, 250 microns thick, for hard-x-ray imaging up to 75 keV. Early test results on these have indicated half-power-diameters of 15 arcsec. The status of these developments will be reviewed.

We have developed a new depth-graded multilayer system comprising W and SiC layers, suitable for use as hard X-ray reflective coatings operating in the energy range 100 - 200 keV. Grazing incidence X-ray reflectance at E=8 keV was used to characterize the interface widths, as well as the temporal and thermal stability in both periodic and depth-graded W/SiC structures, while synchrotron radiation was used to measure the hard X-ray reflectance of a depth-graded multilayer designed specifically for use in the range E~150 - 170 keV. We have modeled the hard X-ray reflectance using newly-derived optical constants, which we determined from reflectance-vs-incidence angle measurements also made using synchrotron radiation, in the range E=120 - 180 keV. We describe our experimental investigation in detail, compare the new W/SiC multilayers with both W/Si and W/B₄C films that have been studied previously, and discuss the significance of these results with regard to the eventual development of a hard X-ray nuclear line telescope.

Following the actual X-ray satellites XMM-NEWTON and CHANDRA future missions are in discussion. ESA is planning the XEUS-satellite and NASA the CONSTELLATION-X mission. The increasing effective areas of the telescopes require nested thin-walled mirrors of large diameters. For the mass production of segmented shells the techniques of nickel electroforming and of epoxy replication are in evaluation. In both cases ZERODUR glass ceramic was chosen for the replication mandrels due to its high thermal stability and its proven ability to be polished to excellent surface qualities. SCHOTT GLAS has produced pre-shaped prototypes of a-spherical replication mandrels. The final polishing is done at CARL ZEISS, who is also the prime contractor for the finished mandrels. A demonstration mandrel for XEUS has been finished in 2000; the first prototype mandrel for CONSTELLATION-X will be delivered this year. It has been demonstrated that high precision mandrels can be produced with the required accuracy. Thereby ZERODUR is developing from a mirror substrate material (ROSAT, CHANDRA) to the preferred material of mandrels for the replication of X-ray mirrors. This demonstrates the broad variety of applications for this zero expansion glass ceramics.

The future X-ray astrophysics space missions require very light-weight but large and precise X-ray mirrors shells. Clearly, developments of innovative techniques and approaches are necessary. We discuss the possible alternative techniques with focus on the technologies and experience available in the Czech Republic. They include light ceramics replication by plasma spraying as well as by CVD and PVD technologies, SiC, thin glass technology, improved electroforming, glossy carbon, as well as glossy metals.

Normal incidence optics have been used with multilayers in EUV region. The 2d of the multilayers has to be equal to the wavelength of interest. At the same time, the reflectivity of the multilayers should decrease with the increase of the interfacial roughness much faster than grazing optics. In general, 2d of 10 nm is the shortest d-spacing available for multilayers in normal incidence. As a challenge of shorter wavelength application, we made NiCr/C multiplayer mirror for the laboratory use at 4.47 nm(carbon K alpha line). The main dish of the Cassegrain optics is 20 cm diameter spherical mirror and the secondary mirror is a reflector in aspherical shape to correct astigmatisms. Its focal point is placed at the X-ray source to create a broad parallel beam of 20 cm in diameter. The flux of the parallel beam is slightly less than the expected value, and gradually decreases of 40% toward the outer region. The measured parallelism is about 25 arcsec, which is a little larger than the designed value. More pricise positioning of the focal point to the X-ray generator may reduce such divergence. The beam profile through a slit shows a core of about 20 arcsec and an extended tail which might be due to scattering tail by the roughness of 0.3 nm. An application of this system is demonstrated with the Astro-E X-ray telescope. The image core is sharper but the scattering tail is considerable. Even after the subtraction of the tail, still some wing is left. This system is bright and parallel enough to examine the optical alignment much faster than previous method, while careful measurements are necessary for quantitative calibration of X-ray telescopes.

A new generation of hard X-ray telescopes using focusing optics are poised to dramatically improve the sensitivity and angular resolution at energies above 10 keV to levels that were previously unachievable by the past generation of background-limited collimated and coded-aperture instruments. Active balloon programs (HEFT, InFocus), possible Explorer-class satellites, and major X-ray observatories (Constellation-X, XEUS) using focusing optics will play a major role in future observations of a wide range of objects including young supernova remnants, active galactic nuclei, and galaxy clusters. These instruments call for grazing incidence optics coated with depth-graded multilayer films to achieve large collecting areas. To accomplish the ultimate goals of the more advanced satellite missions such as Constellation-X, lightweight and low-cost substrates with angular resolution well below an arcminute must be developed. Recent experimental results will be presented on the development of improved substrates and precision mounting techniques that yield sub-arcminute performance.

Next Japanese ASTRO-E2 satellite carries five X-ray telescopes (XRTs), and the pre-collimators for the stray light protection will be installed on them. The pre-collimator is composed of the vertical foil cylinders which line up at the top of the primary reflectors of the XRT. This configuration is effective to reject the stray light of the 'secondary only' reflection, which is the most of the stray light from large off-axis angles up to 70' to the focal plane detector within 18' x 18'. If the height of the pre-collimator is 30 mm (15% of the total height of XRT), we can protect all the "secondary only" component at > 30' off-axis. The field of view will become only about 10% less due to the collimation effect of the 30 mm high pre-collimator. However, new stray light component is generated by the reflection and scattering by the pre-collimator itself, especially at small off-axis angles. As a result, we estimate the total flux of the stray light to be about 10% at 30' off-axis and 5% at 60' off-axis, compared with the case without pre-collimators.

The Constellation-X mission will perform X-Ray science with improvements in energy resolution and effective area over its predecessor missions. The primary instrument on each of the four Constellation-X spacecraft is the Spectroscopy X-Ray Telescope (SXT). The SXT is a 1.6m diameter grazing incidence mirror assembly comprised of approximately 4000 optic elements. In order for the optic elements to work together to achieve the required 15 arcsec image resolution for the telescope, each optic must be aligned very precisely. To enable the alignment of the optic elements to the required tolerances, new technology must be developed through a series of technology demonstrators. The first step in this process is the production of the Optical Assembly Pathfinder (OAP). The OAP represents a small section, or module, of the complete SXT and has been designed to facilitate the evaluation and development of the optic element support, alignment, and adjustment concepts, processes, and procedures. To do this, one pair of optic elements, primary and secondary, will be aligned using optical alignment methods including the Centroid Detector Assembly (CDA) and Interferometry. Ten Optic Adjustment Arms will support the optic elements such that their position and figures can be adjusted. Currently, one section, the primary section, of the OAP has been assembled and is awaiting the installation of an optic element for testing.

Our previous balloon borne experiment, named InFOCuS, proved the imaging capability of the hard X-ray telescope in the energy band above 20 keV. The hard X-ray telescope onboard InFOCuS is the multi-nested thin foil optics using the platinum-carbon depth graded multilayers. Based on the experience of InFOCuS project, we are planing to develop the extremely broad-band X-ray telescope covering the energy range from 0.1 to 80 keV for the future Japanese X-ray astronomical satellite, NeXT (New X-ray Telescope), proposed to launch in 2010. We present here the scientific objectives for X-ray observations in that energy band and the investigation of the requirements for the NeXT X-ray telescope. In order to search the non-thermal emission from the rich clusters of galaxies with cluster-scale radio halo, the required effective area is at least 1000 cm² at 40 keV and the field of view should be larger than 10 arcmin × 10 arcmin. From the effective area estimated from the current design of multilayer parameters, it can be achieved with 4 telescopes with focal length of 12 m and diameter of 60 cm.

X-ray telescopes have been providing high sensitivity in X-ray observations in various missions. Recently XMM-Newton achieved an effective area of about 2000 cm² at 8 keV and a very high sensitivity. For X-ray telescopes in the future, one of the key technologies is to expand the energy band beyond 10 keV. In our previous work, we designed depth-graded multilayers, so called supermirror, for a hard X-ray telescope and it was successfully flown in a balloon flight. This technology is promising to extend the energy band up to 40 keV. We would like to propose supermirror coatings on the mirrors of the XEUS X-ray telescope, which has a focal length of 50 m, a diameter of 4.5 m and a mirror length of 1 m. In this configuration, incident angle is ranging from 0.17 to 0.65 degrees and a large effective area of 30000 cm² at 8 keV can be achieved. To extend the energy band up to 80 keV, platinum-carbon supermirrors are effective for the incident angle below 0.4 degrees. If the inner part of the XEUS mirrors are coated with multilayers, the effective area will be enhanced above 10 keV and be kept over 100 cm2 up to 80 keV. In this paper, we propose the supermirror design and discuss the performance of the XEUS hard X-ray telescope with supermirrors.

We report on the coating of depth graded W/Si multilayers on the thermally slumped glass substrates for the HEFT flight telescopes. The coatings consists of several hundred bilayers in an optimized graded power law design with stringent requirements on uniformity and interfacial roughness. We present the details of the planar magnetron sputtering facility including the optimization of power, Ar pressure and collimating geometry which allows us to coat the several thousand mirror segments required for each telescope module on a time schedule consistent with the current HEFT balloon project as well as future hard X-ray satellite projects. Results are presented on the uniformity, interfacial roughness, and reflectivity and scatter at hard X-ray energies.

We report a new calibration system for large size X-ray optics at ISAS. We adapted a 'dynamical' pencil beam collimated from an X-ray generator, the maximum voltage for which is 50 kV. By combining two stage systems for the X-ray generator and a collimator, the pencil beam dynamically sweeps across a circular region of a telescope with the radius of 60 cm at maximum. In this case, the X-ray telescope and the focal plane detector are both statically fixed. A 4.4~m long rail for detector stage and two positions of the telescope stage provide focal lengths from 4.5 to 12 m, while the previous system can accommodate 4.5 or 4.75 m focal length. The preliminary performance of this system is summarized in this paper. For the post-Astro-EII satellite, a hard X-ray multi-layer supermirror with an unprecedented sensitivity up to 80~keV is strongly expected. This beam facility is of importance because the hard X-ray mirrors always require a long focal length of 8-12 m due to the small reflection angle (about 0.3 degree). Focal length and diameter of future telescopes are always decided by the boundary conditions of the mission at the last moment of the design freeze. Our new X-ray beam facility is designed to match with any kind of X-ray telescope parameters.

X-ray characterization measurements of capillary (X-ray Optical Systems Inc) were carried out at ISAS (Japan) X-ray beam facility. Since capillary system has a capability of collecting x-rays effectively by the small angle reflections in the narrow tubes, it is expected to apply it for the observation of astronomical x-ray objects. The depth of focus on the on-axis is 6 mm, and the image size at the focal plane is 0.4 mm (FWHM) with Cu-K. By using continuum x-ray (2 to 15 keV) beam, the on-axis efficiency was evaluated to be 20 %. The efficiency decreases gradually toward low energy range, this could be explained by the absorption effect of Si which is one of the constituent element of capillary tubes. The field of view is defined as the off-axis angle at which the efficiency becomes half of the on-axis value. The diameter of the field of view was 22', 19' at 4.51 keV and 8.04 keV, respectively. Capillary has no imaging capability, in other words, the light-concentrating direction is independent from the incident angle of x-ray beam. When the x-ray incident angle varies from -15' to +15', the focused images are distributed within 3'. From our measurements, we could confirm the performance of capillary and its potential for astronomical applications.

ASTRO-E2 XRTs adopt Wolter Type-I optics and have nested thin foil structure to enhance their throughput. But this structure allows stray X-rays to come from the sky out of the XRT field of view. Stray light contaminates focal plane images, especially in the case of extended source observations. We intend to mount pre-collimators on top of the ASTRO-E2 XRTs to intercept stray light. On the other hand, reflection by the pre-collimator itself newly creates secondary stray light. To decrease these additional stray light as possible, the mil finish aluminium with its roller mark normal to the incident X-ray beam has been used for the slat material, whose reflectivity is reduced down to 1/20 of ideal specular reflection. Optical profilers tell us these samples have very rough surfaces, whose height varies with Σ; = 1-2 μm. According to the design parameters as are described in the related paper in this symposium (Paper I), an engineering model pre-collimator is fabricated with 46 slats out of 175. Before EM pre-collimator is mounted onto XRT, alignment plates are adjusted to align slats to the same position of XRT primary reflectors. In x-ray measurements, stray light images and the flux of each stray light component at 30' off axis are measured with/without EM pre-collimator. The secondary only reflection component is reduced down to 3.6%, and the backside reflection component becomes more remarkable. On the other hand, X-ray measurement of the effective area at on axis with/without EM pre-collimator verifies that pre-collimator does not interfere the telescope aperture. In addition, the decrease of XRT field of view is ~10%, which is the same as the ray-tracing simulations. As a whole, EM pre-collimator reduces stray light to 27% level with only ~10% decrease of the XRT F.O.V.

We propose a method to make advanced thin-foil substrates for an X-ray telescope by press forming. Walter Type-I optics, which reflect X-rays twice with their confocal paraboloidal and hyperboloidal reflectors, have commonly been used in X-ray astronomy. However, it is difficult to make substrates for a large X-ray telescope with a high imaging quality. By forming two reflectors from one thin substrate, the accuracy of the angle between two reflectors is determined by the accuracy of a mandrel or a stamping die. We made a stamping die using a precision processing method at RIKEN. After several improvements of our pressing method, we have obtained the substrates with a figure error < 15 um, which corresponds to an angular resolution of about 2' at the focal plane, although a small waviness was found in the mirror surface. We also propose a new holding method of the foil to reduce a displacement of the foil positions. The foil is tightly held with three thin-supports with a thickness of 0.3 mm. We made the test model of a mirror housing, and found that the foil position was determined with σ~12μm.

After the design of the calorimeter array for the high-resolution x-ray spectrometer (XRS) on the original Astro-E was frozen, new fabrication techniques became available and our understanding of these devices continually increased. We are now able to complete the optimization of this technology and, potentially, to increase the capability of new XRS instrument for Astro-E2, our on-going sounding recket experiments, and possible further applications. The most significant improvement comes from greatly reducing the excess noise of the ion-implanted thermistors by increasing the thickness of the implanted region.

Active Pixel Sensors (APS) offer high-resolution imaging in combination with a fast and flexible readout. The MPI Halbleiterlabor develops and produces DEPFET (Depleted Field Effect Transistor) based APS devices. They are additionally characterized by enhanced sensitivity for X-ray photons in the range from 0.1 keV to 25 keV, spectroscopic energy resolution (below 1 electron r.m.s.) and radiation hardness. Moreover, the production process on high-ohmic silicon allows incorporating additional high-speed spectrometers based on silicon drift detectors. Such a detector system is proposed as a wide field imager for the XEUS (X-ray Evolving Universe Spectroscopy) mission. XEUS is a planned project within the European Space Agency's Horizon 2000+ program. We will present a focal plane concept for XEUS and measurement results from DEPFET-APS prototypes and high speed drift detectors.

Development of single pixel x-ray microcalorimeters at our institutes, employing superconducting-to-normal phase transition thermometers operating at about 100 mK, generally called Transition-Edge-Sensors (TES), has now resulted in an energy resolution of 3.9 eV FWHM for 5.89 keV x-rays in combination with a response time of 100 μs. Pixel arrays of these detectors, presently under development, will allow for unprecedented x-ray spectroscopy of spatially extended cosmic x-ray sources such as clusters of galaxies, supernova remnants, the galactic diffuse x-ray background and the arm-hot intergalactic medium. Optimization of these cryogenic imaging detectors around 1 keV, in combination with large-area x-ray optics, makes them the most suitable sensor for study of the formation and evolution of hot matter in the universe at large redshift. This detector concept is therefore included in the model payload of the XEUS mission, presently under study by ESA and ISAS. Smaller scale low energy x-ray spectroscopy missions could however generate significant progress in the understanding of supernova remnants, cluster of galaxies and galactic and intergalactic diffuse x-ray emission. This paper presents some science cases, which make explicit use of the unique combination of high efficiency, high spectral resolution and imaging of cryogenic x-ray imaging spectrometers. Furthermore it discusses the present development status of these imaging spectrometers at our institutes, their operating principles and expected performance figures.

XEUS is the post-XMM next generation x-ray observatory which is currently under study by ESA. The mission aims to image the x-ray early universe through the study of feint, high red-shift objects. To provide sufficient photons to enable spectroscopy on these distant objects requires a telescope collecting area greatly in excess of those in use today, and an x-ray optic with collecting area ~100x of XMM is ultimately envisaged. With a focal length of 50m, the plate scale of the optic is 6.5x that of XMM, which using existing focal plane technology will reduce the effective field of view to a few arc minutes. Cryogenic instrumentation, with detector sizes of a few mm can only be used for narrow field studies of target objects, and a wide field instrument is under consideration using a DEPFET pixel array to image out to a diameter of 5 arcminutes, requiring an array of dimension 70mm. Since the useful field of view of the XEUS optic will extend to a diameter of 30 arcminutes, the potential of the optic could be very under-utilized. Here we propose an extension to the wide field imager, the E-WFI, comprised of a ring array of CCDs which will increase the coverage of the focal plane, and greatly increase the serendipitous science resulting from the mission. Here we describe the first design concept for the E-WFI, and discuss the technical advancements in MOS CCD technology which will enhance the science of the mission.

The pn-CCD camera on board of XMM-Newton as well as the Wide Field Imager (WFI) currently being designed for the XEUS mission can be read out in special fast timing modes, providing spectroscopy at very high time resolution. The two fast modes, Timing and Burst mode, of the pn-CCD camera on board XMM-Newton provide a time resolution of 30 μs, respectively. However, this fast timing is only possible at the expense of spatial resolution in readout direction. In contrast, the current baseline design of the WFI for XEUS will provide 25 μs timing at full spatial resolution. We describe the basic principles of the fast readout schemes of the pn-CCD and the SFI, discuss the potential of XEUS for high time resolution spectroscopy and present first results of pulse phase resolved spectroscopy of the Crab pulsar with the pn-CCD in Timing mode.

We present a modeling of the response of a microcalorimeter to the absorption of X-ray photons, based on the main microscopical processes responsible for the energy thermalization. In particular, we have modeled a microcalorimeter with superconducting tin absorber (350 micron x 350 micron x 7 micron) and neutron transmutation doped (NTD) germanium thermistor (75 micron x 50 micron x 150 micron). Such a detector, operated at 60 mK, is expected to achieve a spectral resolution as good as 1 eV FWHM in the soft X-ray energy range, based on the known sources of thermal and electronic noise. Nevertheless, the best spectral resolution measured in laboratory experimental tests is of about 5 eV FWHM (at 5.89 keV). We have investigated how the microscopic processes of energy thermalization, involving both quasiparticles and phonons, and the position of absorption of the photons may affect the spectral resolution of the detector.

We are developing a superconducting transition-edge sensor (TES) calorimeter for future Japanese X-ray astronomy missions (e.g. NeXT mission). The performance of our single pixel TES calorimeter is presented. We fabricated a Ti/Au (40 nm/110 nm) bilayer TES on a thin silicon-nitride membrane, which is adjusted to have a transition temperature of about 100 mK. The size of the TES is 500μm × 500μm, and 300μm × 300μm gold with a thickness of 300 nm is deposited with sputtering as an X-ray absorber. The TES calorimeter was installed in a dilution refrigerator operated at about 40 mK, with a combination of 400-series SQUID array as an ammeter. Collimated 5.9 keV X-rays (200 um in diameter) from 55Fe isotope were irradiated and X-ray pulses were obtained. Simultaneously with a fast falling time constant of 74.2 us, the energy resolution of 6.6+-0.4 eV was attained, while the baseline noise was 6.4 eV. The contents of the energy resolution are 5.1 eV of the excess noise, 3.3 eV of the readout noise, 1.6 eV of the pulse by pulse variation, and 1.9 eV of the intrinsic noise. The baseline noise are dominated by an unknown excess noise, which increases roughly in proportion to the inverse of the TES resistance. The pulse height is sensitive to the operating conditions, and the superconducting shield appears to have improved it by a factor of about 2. The calorimeter works fine over six months surviving five thermal cycles, even though it is kept in air.

The effect of different proton fluences on the performance of two E2V Technologies CCD47-20 devices was investigated with particular emphasis given to the analysis of 'random telegraph signal' (RTS) generation, bright pixel generation and induced changes in base dark current level. The results show that bright pixel frequency increases as the mean energy of the proton beam is increased, and that the base dark current level after irradiation scales with the level of ionization damage. For the RTS study, 500 pixels on one device were monitored over a twelve hour period. This data set revealed a number of distinct types of pixel change level fluctuation and a system of classification has been devised. Previously published RTS data is discussed and reviewed in light of the new data.

The main scientific objective of the ROSITA mission is to extend the X-ray all-sky survey of ROSAT to higher energies to gain an unbiased sample of all types of celestial X-ray sources in the medium energy band. During this mission the whole sky will be scanned by seven imaging X-ray telescopes. The telescopes have different viewing directions with an offset angle between 4 and 6 deg. The focal plane instrumentation of the telescopes is based on a novel type of pn-CCD with a frame store, an advanced version of the pn-CC operating quite successfully on XMM-Newton. The pixel size is adapted to the mirror resolution and the fast readout time guaranties the required angular accuracy despite the scan motion. The X-ray camera carries seven separate CCDs arranged on a circle in the foci of the Wolter type I mirror systems of the seven telescopes. The CCDs are mounted on ceramic frames, which carry dedicated front-end electronics for each CCD. The CCDs are operated at a temperature of-80 deg C. Except for the entrance window, the CCDs are covered by graded shielding for suppression of fluorescent X-ray background, generated by cosmic rays in the surrounding materials. Filters in front of the the CCDs, inhibit optical and UV photons. For in-orbit calibration a radioactive source producing fluorescent X-rays in the desired energy band is provided. We will give an overview of the mechanical, thermal and electrical concept of the camera system.

Over the last six years, we have been developing imaging Cadmium Zinc Telluride pixel detectors optimized for astrophysical focusing hard X-ray telescopes. This application requires sensors with modest area, relatively small pixels and sub-keV energy resolution. For experiments operating in satellite orbits, energy thresholds of ~1-~2 keV are also desirable. In this paper we describe the desired detector performance characteristics, and report on the status of our development effort. In particular, we present results from a 1152-channel custom low-noise VLSI readout designed to achieve excellent spectral resolution and good imaging performance in the 5 -- 100~keV band.

The CACTuS (Compact Array of Cadmium Telluride Micro Spectrometers) instrument was constructed as a prototype detection plane for the Coded Imager and Polarimeter for High Energy Radiation (CIPHER) telescope. The instrument, flown as a 'piggy-back' experiment on a stratospheric balloon as part of the Summer 2002 trans-mediterranean flight campaign from the Milo Italian balloon base in Sicily, was constructed in order to verify the feasibility of using this kind of position sensitive detector for hard X and soft gamma ray polarimetry and imaging, with the objective of studying the instrumental background at stratospheric balloon altitudes over the 20-1000 keV energy range. Of particular interest is the spectrum and distribution of Compton scattered events that trigger two pixel (double) events, the recognition of which is essential for providing a high sensitivity to linear polarisation. It was also used to evaluate the efficiency and the reliability of an off-line numerical algorithm to be applied to the CdTe flight data for signal compensation, which uses the amplitudes obtained by readout electronics with a double shaping filter stage.

We report detector characteristics and background measurements from two prototype imaging CdZnTe (CZT) detectors flown on a scientific balloon payload in May 2001. The detectors are both platinum-contact 10 mm × 10 mm × 5 mm CZT crystals, each with a 4 × 4 array of pixels tiling the anode. One is made from IMARAD horizontal Bridgman CZT, the other from eV Products high-pressure Bridgman CZT. Both detectors were mounted side-by-side in a flip-chip configuration and read out by a 32-channel IDE VA/TA ASIC preamp/shaper. We enclosed the detectors in the same 40o field-of-view collimator used in our previously-reported September 2000 flight. I-V curves for the detectors are diode-like, and we find that the platinum contacts adhere significantly better to the CZT surfaces than gold to previosu detectors. The detectors and instrumentation performed well in a 20-hour balloon flight on 23/24 May 2001. Although we discovered a significant instrumental background component in flight, it was possible to measure and subtract this component from the spectra. The resulting IMARAD detector background spectrum reaches ~5×10^-3 counts cm^-2s^-1keV^-1 at 100 keV and has a power-law index of ~2 at hgih energies. The eV Products detector has a similar spectrum, although there is more uncertainty in the enregy scale because of calibration complications.

The Semiconductor Multiple-Compton Telescope (SMCT) is being developed to explore the gamma-ray universe in an energy band 0.1--20 MeV, which is not well covered by the present or near-future gamma-ray telescopes. The key feature of the SMCT is the high energy resolution that is crucial for high angular resolution and high background rejection capability. We have developed prototype modules for low noise Double-sided Silicon Strip Detector (DSSD) system to realize the SMCT. The geometry of the DSSD is optimized to achieve the lowest noise possible. New frontend LSI optimized for low noise operation is developed. We report on the design and test results of the prototype system. We have achieved an energy resolution of 1.3 keV (FWHM) for 60 keV and 122 keV at 0 degree C.

We report progress in our study of cadmium zinc telluride (CZT) strip detectors featuring orthogonal coplanar anode contacts. We specifically report on the performance, characterization and stability of 5 and 10 mm thick prototype CZT detectors fabricated using material from several manufacturers. Our ongoing work includes laboratory and simulation studies aimed at optimizing and developing compact, efficient, high performance detector modules for 0.05 to 1 MeV gamma radiation measurements with space-based instrumentation. The coplanar anode strip configuration retains many of the performance advantages of pixel detectors yet requires far fewer electronic channels to perform both 3-d imaging and spectroscopy. Minimizing the channel count is important for large balloon or space instruments including coded aperture telescopes (such as MARGIE or EXIST) and Compton imaging telescopes (such as TIGRE or ACT). We also present plans for developing compact, space qualified imaging modules designed for integration into closely packed large area detector arrays. We discuss issues associated with detector module and array electronics design and development.

We present the design and performance of the gamma-ray lens telescope CLAIRE, which flew on a stratospheric balloon on June 14, 2001. The objective of this project is to validate the concept of a Laue diffraction lens for nuclear astrophysics. Instruments of this type, benefiting from the dramatic improvement of the signal/noise ratio brought about by focusing, will combine unprecedented sensitivities with high angular resolution. CLAIRE's lens consists of Ge-Si mosaic crystals, focusing gamma-ray photons from its 505 cm² area onto a small solid state detector, with only 7.2 cm³ volume for background noise. The diffracted energy of 170 keV results in a focal length of 279 cm, yet the entire payload weighed under 500 kg. CLAIRE was launched by the French Space Agency (CNES) from its balloon base at Gap in the French Alps (Southeast of France) and was recovered near Bordeaux in the Southwest of France after roughly 5 hours at float altitude. After presenting the principle of a diffraction lens, the CLAIRE 2001 flight is analyzed in terms of pointing accuracy, background noise and diffraction efficiency of the lens.

B-MINE is a concept for a balloon mission designed to probe the deepest regions of a supernova explosion by detecting ⁴⁴Ti emission at 68 keV with spatial and spectral resolutions that are sufficient to determine the extent and velocity distribution of the ⁴⁴Ti emitting region. The payload introduces the concept of focusing optics and microcalorimeter spectroscopy to nuclear line emission astrophysics. B-MINE has a thin, plastic foil telescope multilayered to maximize the reflectivity in a 20 keV band centered at 68 keV and a microcalorimeter array optimized for the same energy band. This combination provides a reduced background, an energy resolution of 50 eV and a 3F sensitivity in 10⁶ s of 3.3 10^-7 ph cm^-2 s^-1 at 68 keV. During the course of a long duration balloon flight, B-MINE could carry out a detailed study of the 44Ti emission line centroid and width in CAS A.

We are developing a distributed-readout imaging spectrometer named Position-Sensitive Transition-Edge Sensor (PoST). A PoST is a microcalorimeter capagble of 1D imaging spectroscopy. It consists of two Transition-Edge Sensors (TESs) at each end of a long x-ray absorber. The position of an x-ray absorption event in the PoST is determined from the rise time and relative signal sizes in the two sensors. The energy of the absorbed photon is inferred from the sum of the two pulses. We discuss the modeling, operation, and readout of PoSTs and their application to the Constellation-X mission.

The pn-CCD was developed as focal plane detector for the XMM-Newton mission and operates successfully for more than 30 months in orbit without performance degradation. In order to match the new requirements of the future ROSITA mission which will perform a broad band X-ray all-sky survey, we propose an advanced type of pn-CCD. The concept and the new features of this frame store pn-CCD as part of the imaging X-ray spectrometer of ROSITA are described. First measurements with prototype devices show the improvement of detector performance in comparison to the pn-CCD on XMM-Newton. We suggest as optical filter for the observations of the X-ray sky, a thin aluminum layer deposited on the photon entrance window of the device.

We have been developing the hard X-ray telescope using depth graded multilayer. In our balloon experiment launched in 2001 July, we obtained hard X-ray image of Cygnus X-1 in 20-40 keV energy band. We are trying to expand the energy band of X-ray telescope up to 80 keV by optimizing supermirror design. Design of supermirror should achieve high reflectivity and flat response. Moreover, total number of bilayers have to be smaller than 200 for quality of multilayer and fabrication process. In such high energy region (~80 keV), interfacial roughness is serious problem. In practical use, interfacial roughness has to be smaller than 0.3 nm. In our balloon borne experiment, average interfacial roughness of supermirror is about 0.38 nm. We try to improve interface roughness of platinum-carbon multilayer with ion beam sputtering.

Over the last few decades, considerable effort has been expended in adapting a range of group II to VI compound semiconductors for use as photon and charged particle detectors with a particular emphasis on the hard X- and gamma-ray wavebands. Whilst Si and Ge have become detection standards for energy dispersive spectroscopy in the laboratory, their use in commercial and industrial environments is limited - mainly by the need for expensive and bulky cryogenics. Wide-gap compound semiconductors offer the possibility of room temperature operation, while still maintaining sub-keV spectral resolution at hard X-ray wavelengths. At the present time, the performances of such devices are not yet close to the Fano limit (and ultimately, as a result of their higher band-gap, they can never achieve the spectral performances of Si or Ge), however, spectroscopically they can already satisfy the requirements of most of the future anticipated applications above 10 keV. In this paper, we review current progress in compound semiconductors and present results from our development program aimed at producing monolithic compound semiconductor detectors and large area arrays for the next generation X-ray astrophysics and planetary space missions.

Thallium bromide (TlBr) has attracted attention as an exceptional radiation detector material. Due to its high atomic number (81 for Tl, 35 for Br) it has excellent stopping power for hard X-ray and gamma rays and due to its high bandgap (2.7 eV) its operation requires no or only modest cooling. Promising energy resolutions have been demonstrated with detectors fabricated from high-purity samples (3.3 keV for 60 keV photons). These properties make TlBr the material of choice for hard X-ray imaging spectrometers in applications where small weight and/or size is important (e.g. space astrophysics and nuclear medicine). The charge response and spectroscopic performance of a semiconductor imaging array depend not only on material properties but on the pixel properties as well. It has been demonstrated, for instance, that the ratio between pixel size and thickness of the detector is an important factor for the charge response. This is known as the small-pixel or near-field effect. In this paper we investigate the optimization of TlBr pixel properties in a broader context, taking into account material properties (electron and hole mobility, diffusion and trapping), fabrication details and the specific energy range of application, with a view to optimizing both the response and energy resolution.

We propose a new method for absolute calibration of detection efficiency of X-ray detector. The method utilizes measurements with different X-ray incident angles. We first introduce the idea of the method, slant incidence method, in a simplified example. Secondly, we apply the method to measure a filter thickness, using the X-ray CCD camera and a 55Fe isotope source in order to verify our idea. The slant incidence method functions as we expected, but contradiction as large as 30% is observed against the estimates by conventional on-off method. Finally, we apply the slant incidence method to measure the build-in dead layer thickness of an X-ray CCD. using the X-ray spectrometer as a source. We got reasonable estimates for the thickness of the dead layer. An X-ray spectrometer is used to get the ratio of detected intensity of 45"a incidence to that of 0"a incidence as a function of X-ray energy. We get reasonable estimates for the thicknesses of two kinds of dead layers, SiO2 and Si. Discussion on advantages and limitations of this method, and future prospect is mentioned shortly.

The CZT detector on the Infocus hard X-ray telescope is a pixellated solid-state device capable of imaging spectroscopy by measuring the position and energy of each incoming photon. The detector sits at the focal point of an 8m focal length multilayered grazing incidence X-ray mirror which has significant effective area between 20-40 keV. The detector has an energy resolution of 4.0 keV at 32 keV, and the Infocus telescope has an angular resolution of 2.2 arcminute and a field of view of about 10 arcminutes. Infocus flew on a balloon mission in July 2001 and observed Cygnus X-1. We present results from laboratory testing of the detector to measure the uniformity of response across the detector, to determine the spectral resolution, and to perform a simple noise decomposition. We also present a hard X-ray spectrum and image of Cygnus X-1, and measurements of the hard X-ray CZT background obtained with the SWIN detector on Infocus.

We present recent measurements obtained using a new method for characterizing transition edge sensor (TES) calorimeters: We measured the electrical impedance of a TES calorimeter throughout the superconducting to normal metal phase transition. The impedance method enables us to previously measure how the resistance and heat capacity of the TES varied throughout the phase transition. These measurements probe the internal state of oru Mo/Au TES. We also present recent results from measurements of noise in our TESs. Our measurements are instrumental toward understanding and optimizing our TES calorimeters.

We are developing a superconducting Transition-Edge Sensor (TES) calorimeter array. We adopt calorimeter multiplex in frequency domain to read signals from the calorimeter array with a small number of front-end electronics and wirings. We further utilize Calorimeter Bridge Biased by an AC Generator (CABBAGE) approach to eliminate the AC carrier in the output. We tested the method using a TES calorimeter, which has a transition temperature of 390 mK. Because of the high operating temperature, energy resolution of the calorimeter is limited to 200 eV at 5.9 keV even when it is biased with a DC current. We operated the calorimeter in CABBAGE circuit with 30 kHz sinusoidal bias and obtained an energy resolution of 250 eV. We found that there remains a small-amplitude residual in the output even at the bridge balance point. The residual contains not only 30 kHz component but also odd-order harmonics. We consider that this is due to the variation of the TES resistance with bias current. The 50 eV degradation of the energy resolution from DC to AC biases can be explained by the fact that some of signal power is carried in the odd-order harmonics, which we did not utilize in the data reduction process. We also succeeded to operate the CABBAGE by 100 kHz, although the energy resolution was degraded to 380 eV probably due to low response of the signal readout circuit at the frequency.

We report on design updates for the XIS (X-ray Imaging Spectrometer) on-board the Astro-E2 satellite. Astro-E2 is a recovery mission of Astro-E, which was lost during launch in 2000. Astro-E2 carries a total of 5 X-ray telescopes, 4 of which have XIS sensors as their focal plane detectors. Each XIS CCD camera covers a field of view of 19×19 arcmin in the energy range of 0.4-12 keV. The design of the Astro-E2 XIS is basically the same as that for Astro-E, but some improvements will be implemented. These are (1) CCD charge injection capability, (2) a revised heat-sink assembly, and (3) addition of a 55Fe radio-isotope on the door. Charge injection may be used to compensate for and calibrate radiation-induced degradation of the CCD charge transfer efficiency. This degradation is expected to become significant after a few year's operation in space. The new heat-sink assembly is expected to increase the mechanical reliability and cooling capability of the XIS sensor. The new radio-isotope on the door will provide better calibration data. We present details of these improvements and summarize the overall design of the XIS.

The Chandra ACIS has seriously damaged by the low energy proton in orbit. Radiation hardness is an important characteristics of a device in space use. Therefore we applied the mesh experiment to a relatively low energy proton beam employing the CCD developed for the MAXI~(Monitor of All-sky X-ray Image) CCD camera named SSC that is scheduled to be onboard the International Space Station~(ISS) in 2005. It consists of 1024×1024 pixels with 24μm square. It is equipped with a `notch' structure in the middle of the pixel so that it is designed to be radiation hard. A mesh experiment is, so far, the only practical technique to study the CCD response with subpixel resolution. The mesh is made of gold with 10μm thick with many holes of 2μm in diameter. The proton beam is controlled so that the proton passing through the mesh hole can penetrate into the CCD chip with leaving damages near the buried channel inside.

At DSRI, in collaboration with the cyclotron facility at Copenhagen University Hospital, we have performed a study of radiation effects exposing a 2.7 mm thick CZT drift strip detector to 30 MeV protons. The detector characteristics were evaluated after exposure to a number of dose loads in the range from 2*10⁸ to 60*10⁸ p⁺/cm². Even for the highest dose loads, which had a dramatic effect on the spectroscopic performance, we were able to recover the detectors after an appropriate annealing procedure. The radiation damage was studied as function of depth inside the detector material. A numerical model that emulates the physical processes of the charge transport in the CZT detector was used to derive the charge trapping parameter , μτ_e (the product of charge mobility and trapping time) as function of dose. The analysis showed that the electron trapping increased proportional with the proton dose. The radiation contribution to the electron trapping was found to obey the following relation: (μτ_e)^-1_rad =(2.5±0.2)*10^-7*Φ (V/cm²) with the proton fluence, Φ in p⁺/cm². The trapping depth dependence, however, did not agree well the damage profile calculated using the standard Monte Carlo simulations, TRIM for the proton induced radiation effects. The present results suggest that proton induced nuclear reactions contribute significantly to the radiation damage. Further work will elaborate on these effects. The detector energy resolution was investigated as function of proton dose. It was found that the observed degradation is well explained by the decrease of μτ_e when the fluctuations of the electron path length are taken into account. The proton irradiation produced In meta stable isotopes in the CZT material. Their decay and production yield as function of depth were analyzed.

We report on the background study of the CCD camera of the MAXI mission on-board the International Space Station. Our study is based on the simulation using the Geant4 toolkit. We studied the background from cosmic electron in 3-100MeV range mainly. Our result shows that the design of collimator and slit is important to reduce the X-ray background (mainly bremsstrahlung). Thick collimator and slit is preferable. Material is also important.

We have investigated the radiation damage effects on a CCD to be employed in the Japanese X-ray astronomy mission including the Monitor of All-sky X-ray Image (MAXI) onboard the International Space Station (ISS). The X-ray CCD camera, ACIS, onboard Chandra have been seriously damaged by low energy protons having energy of ~150,keV since low energy protons release their energy mainly at the charge transfer channel, resulting a decrease of the charge transfer efficiency. We thus focused on the low energy protons in our experiments. A 171 keV to 3.91 MeV proton beam was irradiated to a given device. We measured the degradation of the charge transfer inefficiency (CTI) and dark current as a function of incremental fluence. A 292 keV proton beam degraded the CTI most seriously. Taking into account the proton energy dependence of the CTI, we confirmed that the transfer channel has a lowest radiation tolerance. On the other hand, dark current increased after proton irradiation for all energies except 171 keV. We have also developed the different device architectures to reduce the radiation damage in orbit. We then investigated the spatial distribution of the low energy protons in the orbit of the ISS. We found that their density has a peak around l ~20° and b ~-55° independent of the attitude. The peak value is roughly two orders of magnitude larger than that at the South Atlantic Anomaly. Taking into account the new anomaly and orbit of the ISS, we estimated the charge transfer inefficiency of MAXI CCDs to be 1.1 × 10^-5 per each transfer after two years of mission life in the worse case analysis if the highest radiation-tolerant device is employed. This value is well within the requirement and we have confirmed the high radiation-tolerance of MAXI CCDs.

The Quasiparticle Trapping Transistor (QuaTraTran, QTT) was proposed by Booth et al. as a new, multi-purpose superconducting electronic device for the amplification of low-level electrical signals at low temperatures. In this paper we consider its application as a cold 'pre-preamplifier' for signals coming from a superconducting tunnel junction (STJ) used as a soft X-ray detector. The mplification of signals in an STJ itself relies on multiple tunneling of quasiparticles, which has a large associated noise when compared to the Fano noise. In the soft X-ray domain (i.e for photon energies < 1 keV), tunnel noise is the limiting factor for the energy resolution. The amplification in a QTT, on the other hand, depends on the down-conversion of quasiparticles at the superconducting gap of a superconducting metal to the Fermi level when they enter a normal metal. The charge created in the absorber layer tunnels through an asymmetric SIS' junction with a high tunnel probability in one direction only. This SIS' junction is in direct contact with a NIS junction, together forming the QTT. We investigate the prospects of applying QTT read-out to a strip detector, and its possible advantages over a design based on STJs. The goal is to improve on the energy resolution of STJs, while retaining the advantages of the STJ approach, such as its application in imaging detectors and single photon detection. Estimates are made of influences on the noise of the SIS part of the QTT, the down-conversion process, thermal quasiparticles and recombination and thermal phonons.

We present the design and initial flight results of a balloon-borne hard X-ray detector system for observing high-resolution spectra of solar flares. The instrument is designed to achieve a 3 keV energy resolution over the energy range of 15-120 keV. The instrument uses sixteen 10×10×0.5mm cadmium telluride (CdTe) detectors with indium electrodes that act as Schottky barriers. Pre-flight tests confirmed that all detectors exceeded the target 3 keV resolution. The detector system is designed to optimize radiative cooling in order to achieve the operating temperature of 0°C without refrigeration mechanisms. The first flight took place on August 29, 2001 and while no major flares were observed, the instrument operation was verified and a detector temperature of -13° C was achieved. The second flight took place on May 24, 1974 and during the 8 hours of level flight at an altitude of 41km, we succeeded in observing a class M1.1 solar flare.

The second of NASA's 'Great Observatories', the Compton Gamma Ray Observatory (CGRO) was one of NASA's most successful missions. The scientific results changed our view of the hig-energy Universe in many fundamental ways. Originally designed as a two-year mission, CGRO continued to return hgih quality scientific data until a reference-gyro failure led NASA to de-orbit the spaceraft after nine years of operations while the capability for a controlled reentry remained. Success is a result of careful planning and wise leadership. It is useful to examine how such a mission was designed, developed, and implemented, as a model for future scientific missions. Careful scientific planning, a highly skilled and motivated project staff who worked closely with the scientists, a close working relationship with TRW, the mission contractor, a dedicated operations crew and strong support from the management of the Goddard Space Flight Center were all important to the success of CGRO. It is the purpose of this paper to examine CGRO activities from the initial science planning beginning in the eraly 1970's to the end of mission funding in 2002 to see what can be learned from the successes and the failures of this grand mission.

INTEGRAL is ESA's next gamma-ray astronomy mission and is set for launch on 2002 October 17, from Baikonur on a Russian Proton rocket into a 72 hour orbit with an apogee of 150,000 km and a perigee of 10,000 km. INTEGRAL will study some of the most extreme objects in the Universe such as black holes, neutron stars and the mysterious gamma-ray bursts, the most energetic explosions known. The payload consists of two gamma-ray telescopes - SPI, or Spectrometer on INTEGRAL, which will measure gamma-ray energies very precisely and IBIS, or Imager on Board the INTEGRAL Satellite, which will provide very fine images. The sensitivity of INTEGRAL is extended to lower energies by x-ray and optical monitors - the Joint European X-ray Monitor and the Optical Monitoring Camera. The improved imaging and spectral capabilities of INTEGRAL compared to previous gamma-ray missions, as well as the board-band monitoring will provide the scientific community with an unprecedented opportunity to investigate the nature of the extreme Universe.

The spectrometer SPI - one of the two main instruments aboard ESA's INTEGRAL - is dedicated to high resolution gamma-ray line spectroscopy with modest imaging. SPI will mainly concentrate on the study of lines from radioactive isotopes. A wealth of new information is expected from interstellar line emission with narrow line profiles. But existing results are also expected from profile measurements of individual line emitting objects such as supernovae, supernova remnants, novae or stellar black hole systems. In addition, sensitive measurements of continuum emission from compact sources and from interstellar space are expected, especially in the sub-MeV region.

IBIS, the INTEGRAL gamma-ray telescope designed to produce high-resolution images (12') over a wide field of view, covers the energy range 15 keV - 10 MeV. Its high sensitivity (mCrab level) and accurate timing (0.1 ms) are particularly well adapted to the study of the galactic and extragalactic accretion powered sources. Weekly scans of the galactic disc will allow for the detection of transient sources (e.g. X-ray novae) that may be considered as targets of opportunity. The spectral performance of IBIS (10% at 60 keV) will allow for the study of line emission from supernova remnants (⁴⁴Ti), pulsars (cyclotron lines) and X-ray novae. The wide field of view will permit the detection of many serendipitous sources such as AGNs and gamma-ray bursts. The polarimetric capabilities of the telescope may also give new insights into the gamma-ray burst phenomenon.

SPI, the Spectrometer on board the ESA INTEGRAL satellite, to be launched in October 2002, will study the gamma-ray sky in the 20 keV to 8 MeV energy band with a spectral resolution of 2 keV for photons of 1 MeV, thanks to its 19 germanium detectors spanning an active area of 500 cm². A coded mask imaging technique provides a 2° angular resolution. The 16° field of view is defined by an active BGO veto shield, furthermore used for background rejection. In April 2001 the flight model of SPI underwent a one-month calibration campaign at CEA in Bruyères le Châtel using low intensity radioactive sources and the CEA accelerator for homogeneity measurements and high intensity radioactive sources for imaging performance measurements. After integration of all scientific payloads (the spectrometer SPI, the imager IBIS and the monitors JEM-X and OMC) on the INTEGRAL satellite, a cross-calibration campaign has been performed at the ESA center in Noordwijk. A set of sources has been placed in the field of view of the different instruments in order to compare their performances and determine their mutual influence. We report on the scientific goals of this calibration activity, and present the measurements performed as well as some preliminary results.

The Gamma-ray Large Area Space Telescope (GLAST) is the next orbiting high-energy gamma-ray mission, scheduled for launch by NASA in 2006. The GLAST Observatory will have two scientific instruments: (1) the Large Area Telescope (LAT), an imaging, wide field-of-view telescope sensitive to radiation over the energy range from ~20 MeV to more than 300 GeV, and (2) the GLAST Burst Monitor (GBM), sensitive to transient bursts from 10 keV to 25 MeV. The GBM is described elsewhere in this proceedings by Lichti, et al. The LAT, a pair-conversion telescope, is being developed by an international collaboration from the United States, France, Italy, Japan, and Sweden. It will have sensitivity more than 40 times better than that of EGRET. In this paper the LAT instrument, its expected performance, and the current state of its development are described.

AGILE is an ASI gamma-ray astrophysics space Mission which will operate in the 30 MeV - 50 GeV range with imaging capabilities also in the 10 - 40 keV range. Primary scientific goals include the study of AGNs, gamma-ray bursts, Galactic sources, unidentified gamma-ray sources, diffuse Galactic and extragalactic gamma-ray emission, high-precision timing studies, and Quantum Gravity testing. The AGILE scientific instrument is based on an innovative design of three detecting systems: (1) a Silicon Tracker, (2) a Mini-Calorimeter, and (3) an ultralight coded mask system with Si-detectors (Super-AGILE). AGILE is designed to provide: (1) excellent imaging in the energy bands 30 MeV-50 GeV (5-10 arcmin for intense sources) and 10-40 keV (1-3 arcmin); (2) optimal timing capabilities, with independent readout systems and minimal deadtimes for the Silicon Tracker, Super-AGILE and Mini-Calorimeter; (3) large field of view for the gamma-ray imaging detector (~3 sr) and Super-AGILE (~1 sr). AGILE will be the only Mission entirely dedicated to source detection above 30 MeV during the period 2004-2006.

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is a NASA Small Explorer satellite designed to study hard x-ray and gamma-ray emission from solar flares. In addition, its high-resolution array of germanium detectors can see photons from high-energy sources throughout the Universe. Here we discuss the various algorithms necessary to extract spectra, lightcurves, and other information about cosmic gamma-ray bursts, pulsars, and other astrophysical phenomena using an unpointed, spinning array of detectors. We show some preliminary results and discuss our plans for future analyses. All RHESSI data are public, and scientists interested in participating should contact the principal author.

Swift is a first-of-its-kind multiwavelength transient observatory for gamma-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of gamma-ray bursts and their afterglows, as well as for using bursts to probe the early Universe. Swift will also monitor the soft gamma repeaters and perform the first sensitive hard X-ray survey of the sky. The mission is being developed by an international collaboration and consists of three instruments, the Burst Alert Telescope (BAT), the X-ray Telescope (XRT), and the Ultraviolet and Optical Telescope (UVOT). The BAT, a wide-field gamma-ray detector, will detect >100 gamma-ray bursts per year with a sensitivity 5 times that of BATSE. The sensitive narrow-field XRT and UVOT will be autonomously slewed to the burst location within 20 to 70 seconds to determine 0.3-5.0 arcsec positions and perform optical, UV, and X-ray spectrophotometry. Strong education/public outreach and follow-up programs will help to engage the public and the astronomical community. Swift launch is planned for September 2003.

One of the scientific objectives of the GLAST mission is the study of gamma-ray bursts (GRBs) which will be measured by the Large-Area Telescope, the main instrument of GLAST, in the energy range from ~20 MeV to ~300 GeV. In order to extend the energy measurement towards lower energies a secondary instrument, the GLAST Burst Monitor (GBM) will measure GRBs from ~10 keV to ~25 MeV and will thus allow the investigation of the relation between the keV and the MeV-GeV emission from GRBs. The GBM consists of 12 circular NaI crystal discs and 2 cylindrical BGO crystals. The NaI crystals are optimized for gamma radiation from ~10 keV to ~1 MeV and the BGO crystals from ~150 keV to ~25 MeV. The NaI crystals are oriented in such a way that the measured relative counting rates allow a rapid determination of the position of a gamma-ray burst within a wide FoV of ~8.6 sr. This position will be communicated within seconds to the LAT which may then be reoriented to observe the long-lasting high-energy gamma-ray emission from GRBs. This will allow the exploration of the unknown aspects of the high-energy burst emission and their connection with the well-known low-energy emission. Another important feature of the GBM is its high time resolution of ~10 microseconds for time-resolved gamma-ray spectroscopy.

ECLAIRs is a microsatellite devoted to the multi-wavelength observation of the prompt emission of GRBs. For about 100 GRBs per year, ECLAIRs will provide high time resolution high sensitivity spectral coverage from a few eV up to a few hundred keV and localization to 10' in near real time. This capability is achieved by combining wide field optical and X-ray cameras sharing a common field of view with a coded-mask gamma camera providing the trigger and the localization of the bursts. ECLAIRs relies upon an international collaboration involving theoretical and hardware groups from Europe and the United States. In particular, it builds upon the extensive knowledge and expertise that is currently being gained with missions such as HETE-2 and INTEGRAL.

LXeGRIT is the first prototype of a novel concept of Compton telescope, based on the complete 3D reconstruction of the sequence of interactions of individual γ-rays in one position sensitive detector. This balloon-borne telescope consists of an unshielded time projection chamber with an active volume of 400 cm² × 7 cm filled with high purity liquid xenon. Four VUV PMTs detect the fast xenon scintillation light signal, providing the event trigger. 124 wires and 4 anodes detect the ionization signals, providing the event spatial coordinates and total energy. In the period 1999-2001, LXeGRIT has been extensively tested both in the laboratory and at balloon altitude, and its response in the MeV region has been thoroughly characterized. Here we summarize some of the results on pre-flight calibration, even reconstruction techniques, and performance during a 27 hour balloon flight on October 4-5. We further present briefly the on-going efforts directed to improve the performance of this prototype towards the requirements for a base module of a next-generation Compton telescope.

A new telescope for Medium Energy Gamma-Ray Astronomy, MEGA, is being developed for the energy band 0.4 - 50 MeV as a successor to COMPTEL on CGRO. MEGA aims to improve the sensitivity for astronomical sources by at least an order of magnitude with respect to past instruments and will fill a severe sensitivity gap between already scheduled hard-X-ray and high-energy gamma-ray missions. MEGA records and images gamma rays by completely tracking Compton and pair creation events in a stack of double sided Si-strip track detectors surrounded by a pixelated CsI calorimeter. MEGA will have an effective area of ~100 square cm, a large field of view of ~130 degrees, angular resolution of ~2 degrees, and energy resolution of ~8% (all FWHM at ~2 MeV). Key science objectives for MEGA are the investigation of cosmic high-energy accelerators, nucleosynthesis sites with gamma-ray lines, and the mapping of large-scale structures in the Galaxy and beyond. If operated on a zenith pointing satellite MEGA will be an ideal continuous all-sky monitor for transient sources. This paper describes the development of a small scale prototype and the concept of a space mission for MEGA.

Our collaboration is developing a 2-detector prototype high resolution Compton telescope utilizing 3D imaging germanium detectors (GeDs) for a test balloon flight in Spring 2003. This instrument is a prototype for a full 12-GeD instrument, the Nuclear Compton Telescope. NCT is a balloon-borne soft gamma-ray (0.2-15 MeV) telescope designed to study astrophysical sources of nuclear line emission and polarization. The NCT program is designed to develop and test the technologies and analysis techniques crucial for the Advanced Compton Telescope, while studying gamma-ray radiation with very high spectral resolution, moderate angular resolution, and high sensitivity. NCT has a novel, ultra-compact design optimized for studying nuclear line emission in the critical 0.5-2 MeV range, and polarization in the 0.2-0.5 MeV range. This prototype flight will critically test the novel instrument technologies, analysis techniques, and background rejection procedures we have developed for high resolution Compton telescopes. We present the design and expected performance of this prototype NCT instrument.

A multi-Compton gamma-ray telescope based on high resolution semiconductor materials (Semiconductor Multi-Compton Telescope (SMCT) or Advanced Compton Telescope (ACT)) is a promising approach to achieve high sensitivity for gamma-rays with energies from several hundred keV up to several MeV. A SMCT utilizing several tens of layers of thin CdTe (Cadmium Telluride) detector is an attractive concept to obtain higher detection efficiency in comparison with Si-based SMCT. Recently we have developed high energy-resolution CdTe diode detectors. A large-area detector with dimensions of 2.15 × 2.15 cm² with a thickness of 0.5mm shows an energy resolution of better than 3 keV (FWHM) at 60 keV. In order to extend the application of CdTe diodes to the detection of MeV gamma-rays, we have constructed a stacked detector consisting of 40 layers of large CdTe diodes. Here we report the recent progress on the high-resolution CdTe diode and describe the conceptual design of new Multi-Compton Gamma-ray telescopes based on Monte Carlo simulation. An idea of active pair production telescope is briefly described.

The Advanced Compton Telescope (ACT) should provide well over an order-of-magnitude improvement in sensitivity compared to other previous or planned instruments in low-energy gamma-ray astronomy. This will be needed in the study of the nuclear line/MeV region of the gamma-ray spectrum. Such an instrument covers a broad range of science objectives, ranging from the study the ⁵⁶Ni light curves of supernovae and provide measurements of supernova dynamics, to ²⁶Al, ²²Na, and ⁶⁰Fe maps of the galaxy, and the first gamma-ray polarization observations probing the geometry of the emission regions of a variety of objects such as AGN, pulsars, and gamma ray bursts. These objectives depend critically on the sensitivity that can be achieved. We present a study of the sensitivity that can be achieved by the ACT, considering estimates of backgrounds, position resolution, energy resolution, Doppler broadening, and recoil electron tracking. Efficiency questions are considered that arise from passive materials within the active volume and track reconstruction. A sensitivity estimate for ACT is presented for a reasonable instrument size and configuration.

The gamma-ray telescope IBIS, on Board the INTEGRAL satellite, is expected to satisfy the mission's imaging objectives, by using two position sensitive detection planes, one with 16384 Cadmium Telluride pixels (ISGRI) at lower energies and the other with 4096 Caesium Iodide pixels (PICsIT) for higher energy detection. Given to the high complexity of the system, a dedicated Experiment Check Out Equipment (ECOE), was developed, capable not only to acquire, archive and monitor, the instrument data, but also to perform a fast data analysis, in order to deeply understand the instrument behavior in real-time. The system was used to support the IBIS Test and Calibration campaign campaigns, from the Engineering to the Flight model, and it will be used again during the Commissioning Phase, after launch. We describe here, the architecture of the ECOE system and the quick-look analysis tools that, with an user friendly graphical interface, allows the user to analyze, in an easy way, both the IBIS housekeeping and scientific data.

The INTEGRAL gamma-ray observatory is due to be launched in October 2002 on a Proton rocket from the Russian base in Baikonur in Kazakhstan. Its scientific payload contains two main instruments on board, one dedicated to spectrometry (SPI) and with moderate imaging capabilities, and the other (IBIS) designated to produce high angular resolution images with moderate energy resolution, in addition to X-ray and Optical monitors. The IBIS telescope itself consists of two main subsystem: a low energy (15 keV - 1 MeV) detector (ISGRI) and a plane (PICsIT) working at higher energies (170 keV - 10 MeV). Both these instruments use the same coded aperture mask in order to create images of the sky over the entire energy range with a resolution of 12 arcminutes and point source location accuracy down to tens of arcseconds for the strongest sources. The data from the satellite will be trasmitted to the INTEGRAL Science Data Centre (ISDC) located near Geneva for initial processing and distribution of the analysis results. The quantity of data is large, and each observation will typically consist of many individual pointings around the target, which will then be summed together. This allows a reduction of systematic effects in the creation of the spectral imaging images. Herein we describe the data structure of the PICsIT instrument from raw low-level data through to the high-level scientific products, indicating how the data sets are used to obtain images and spectra for celestial gamma-ray sources.

The IBIS telescope is the high angular resolution Gamma-Ray imager on-board the ESA satellite INTEGRAL. The scientific goal of IBIS is to address, complemented by the high resolution spectrometer (SPI), astrophysical processes from celestial sources and diffuse regions in the X and Gamma-Ray domain. IBIS, with its Cadmium Telluride detector of 16.384 pixels and Caesium Iodide detector of 4.096 pixels, is an instrument with an high degree of complexity, whose status is continuously monitored by thousands of parameters (count rates, temperatures, voltages, instruments status, etc.), transmitted to ground by the periodic and non-periodic satellite telemetry housekeeping packets. In this paper we present the 'Ibis Parameters MONitor' (IPAMON), the real-time quick look software, part of the IBIS Experiment Check Out Equipment (ECOE), used during the on-ground functional and calibration campaign of the IBIS flight model carried out in LABEN (Milano) and ESTEC (ESA, Noordwijk). Due the high number of parameters, the software was designed to be flexible. In fact using the instrument data base as input for the internal structure configuration, the software is then insensitive to modifications that can occurs in the contents of the packet telemetry. This capability allows IPAMON to be easily used for any other mission involving ESA packet structured telemetry.

ESA's INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) will be launched in October 2002. Its two main instruments are the imager IBIS and the spectrometer SPI. Both emply coded apertures to obtain directional information on the incoming radiation. SPI's detection plane consists of 19 hexagonal Ge detectors, its coded aperture has 63 tungsten-alloy elements of 30 mm thickness.

LXeGRIT is the first prototype of a novel Compton telescope for MeV γ-ray astrophysics based on a Liquid Xenon Time Projection Chamber (LXeTPC), sensitive in the energy band of 0.15-10 MeV. In this homogeneous, 3D position sensitive detector, γ-rays with at least two interactions in the sensitive volume of 2800 cm³, are imaged as in a standard Compton telescope. γ-rays with a single interaction cannot be imaged and constitute a background which can be easily identified and rejected. Charged particles and localized β-particles background is also easily suppressed based on the TPC localization capability with millimeter resolution. A measurement of the total γ-ray background rate in near space conditions and the background rejection power of the LXeTPC was a primary goal of the LXeGRIT balloon flight program. We present here a preliminary analysis addressing this question, based on balloon flight data acquired during the Oct 4-5, 2000 LXeGRIT balloon flight from Ft. Sumner, NM. In this long duration balloon experiment, the LXeGRIT TPC was not surrounded by any γ-ray or charged particle shield. Single site events and charged particles were mostly rejcted on-line at the first and second trigger level. The remaining count rate of single-site γ-ray events, at an average atmospheric depth of 3.2 g cm^-2, is consistent with that expected from atmospheric and diffuse γ-ray background, taking into account the instrument mass model and response.

Many expectations are haven to the INTEGRAL satellite and the development and plan of devices in the next generation, which will exceed existing devices in a future, are also in progress. As a detector technology for the next generation, we have developed a liquid Xe Time Prjection Chamber(TPC) for MeV gamma-ray observations. It is designed to image gamma-rays in the energy range of about ~200keV to 10 MeV. The chamber consists of two sensitive volumes of 20cm×20cm×5cm. Two anode systems are at the center of effective area and made with a print substrate that has strip type anodes and induction electrodes.

The angular resolution of a telescope which detects gamma-rays via the Compton effect is fundamentally limited below a few hundred keV by the fact that the target electrons have an indeterminable momentum inside their atoms which introduces an uncertainty in the recoil energy of the Compton electron and the scattered photon. This additional component in the energy and momentum equation results in a Doppler broadening of the angular resolution compared to the standard Compton equation for a target at rest. The deterioration in resolution is most pronounced for low photon energy, high scatter angle, and high Z of the scatter material. This physical limit to the angular resolution of a Compton telescope is present even if all other parameters (e.g. energy and position) are measured with high accuracy. For different Compton scatter materials such as silicon, germanium and xenon, which are used in current telescope designs, the best possible angular resolution as a function of photon energy and scatter angle is calculated. Averaged over all scatter angles and energies, the Doppler-limited angular resolution of silicon is a factor of ~1.6 better than that of germanium and a factor of ~1.9 better than that of xenon. Looking at the Doppler limit of materials from Z=1 to 90 the best angular resolution can be reached for alkaline and alkaline earth metals, the worst for elements with filled p-orbitals (noble gases) and d-orbitals (e.g. Pd and Au). Of all semiconductors which might be used in a next generation Compton telescope, silicon seems to be the best choice.

The Wide-field X-ray Monitor (WXM) is one of the scientific instruments carried on the High Energy Transient Explorer 2 (HETE-2) satellite launched in October 2000. The WXM consists of three elements: (1) four identical Xe-filled one-dimensional position-sensitive proportional counters, two in the spacecraft X-direction and two in the Y-direction, (2) two sets of one-dimensional coded apertures orthogonally mounted above the counters in the X and Y-direction, and (3) the main electronics that processes analog signals from the counters. The WXM counters are sensitive to X-rays between 2 keV and 25 keV within a field-of-view of about 1.5 sr with a total detector area of about 350 cm². The combination of the apertures and the counters provides GRB locations with accuracy ~10 arcmin. The counters and electronics are developed and fabricated by RIKEN, and the apertures and on-board software are designed and provided by Los Alamos National Laboratory. The WXM plays a major roll in the GRB localization and its spectroscopy in the energy range between 2 keV and 25 keV. During the first year of observations, a number of steady X-ray sources as well as high-energy transients were detected with the WXM. Observing Crab nebula and Sco X-1, we have calibrated the detector alignment between the WXM and the optical camera system with 2 arcmin accuracy. As of 29 July 2002, nineteen GRBs have been localized with the WXM in the 18 months of stable operations. Twelve of them were reported to the GCN within a delay of 10 hours, and 4 optical transients were identified by ground based telescopes. The energy response of the detectors has also been calibrated using the Crab spectrum. We report the in-orbit performance of the WXM instrument during the first 18 months.

The Swift Gamma-Ray Burst Explorer will be launched late in 2003 to make prompt multiwavelength observations of Gamma-Ray Bursts and Afterglows. The X-ray Telescope (XRT) provides key capabilities that permit Swift to determine GRB positions with several arcsecond accuracy within 100 seconds of the burst onset. The XRT is designed to observe GRB afterglows covering over seven orders of magnitude in flux in the 0.2-10 keV band, with completely autonomous operation. GRB positions are determined within seconds of target acquisition, and accurate positions are sent to the ground for distribution over the GCN. The XRT can also measure redshifts of GRBs for bursts with Fe line emission or other spectral features.

The 2.6 square meter coded aperture mask is a vital part of the Burst Alert Telescope on the Swift mission. A random, but known pattern of more than 50,000 lead tiles, each 5 mm square, was bonded to a large honeycomb panel which projects a shadow on the detector array during a gamma ray burst. A two-year development process was necessary to explore ideas, apply techniques, and finalize procedures to meet the strict requirements for the coded aperture mask. Challenges included finding a honeycomb substrate with minimal gamma ray attenuation, selecting an adhesive with adequate bond strength to hold the tiles in place but flexible enough to allow the tiles to expand and contract without distorting the panel under large temperature gradients, and eliminating excess adhesive from all untiled areas. Finding an efficient way to bond the > 50,000 lead tiles to the panel while maintaining positional tolerances within +0.1 mm was no small task. In order to generate the desired bondline, adhesive was applied and allowed to cure to each tile. The 'pre-cured' tiles were located in a tool to maintain positional accuracy, wet adhesive was applied to the panel, and the wetted substrate was lowered to the tile surface with synchronized actuators. Using this procedure, the entire tile pattern was transferred to the large honeycomb panel in a single bond. The pressure for the bond was achieved by enclosing the entire system in a vacuum bag. Thermal vacuum and acoustic tests validated this approach. This paper discusses the methods, materials, and techniques used to fabricate this very large and unique coded aperture mask for the Swift mission.

The spectrometer SPI, one of the two main instruments of the INTEGRAL spacecraft, has strong capabilities in the field of Gamma-Ray Burst (GRB)detections. In its 16° field of view (FoV) SPI is able to trigger and to localize GRBs. With its large anticoincidence shield (ACS) of 512 kg of BGO crystals SPI is able to detect GRBs quasi omnidirectionally with a very high sensitivity. The ACS GRB alerts will provide GRB arrival times with high accuracy but with no or very rough positional information. The expected GRB detection rate in SPI's FoV will be one per month and for the ACS around 300 per year. At MPE two SPI software contributions to the real-time INTEGRAL burst-alert system (IBAS) at the INTEGRAL science data centre ISDC have been developed. The SPI-ACS branch of IBAS will produce burst alerts and light-curves with 50 ms resolution. It is planned to use ACS burst alerts in the 3rd interplanetary network. The SPI-FoV branch of IBAS is currently under development at MPE. The system is using the energy and timing information of single and multiple events detected by the Germanium-camera of SPI. Using the imaging algorithm developed at the University of Birmingham the system is expected to locate strong bursts with an accuracy of better than 1°.

The Swift X-ray Telescope (XRT)[1] is designed to make astrometric, spectroscopic, and photometric observations of X-ray emission from Gamma-ray Bursts and their afterglows in the energy band 0.2-10 keV. The XRT has a variety of readout modes which it automatically selects in order to observe objects covering 7 orders of magnitude in flux and to extract the maximum possible science from each one, in response to the flux from the burst diminishing. The primary goal of the XRT is to locate the position of the Gamma-Ray Burst to 1 arcsec and to transmit this position to the UVOT and the ground within 100 seconds of the initial observation of the burst. We describe in detail the use of imaging mode and a centroid algorithm to determine the position of the Gamma-Ray Burst with sub-pixel accuracy.

We have studied the design of astronomical multilayer telescopes optimized for performance from 5 to 200 keV. This region of the spectrum contains important nuclear lines that are observable in supernovae and their remnants. The study of these lines can help to differentiate currently competing theories of supernova explosion. Our telescope design will enable us to measure the spectral lines of isotopes such as Ni-56 in Type Ia supernovae and Ti-44 in core-collapse remnants, as well as to observe active galactic nuclei at gamma-ray energies. We considered the performances of multilayers of various material pairs, including W/Si, Pt/C and Ni93V7/Si, as employed in conical-approximation Wolter I optics. We experimented with dividing the energy band of interest into several sections, and optimizing different groups of mirror shells within a single telescope for each smaller energy band. Different material pairs are also used for different energy bands, in order to obtain a higher overall performance. We also consider the significance of the energy bandwidth on the effectiveness of Joensen's parametrization of the multilayer thickness profile, and on the mirror performance within the band.

Fresnel lenses can focus gamma-rays by using a combination of diffraction and refraction. Such lenses (and variations on them in which the chromatic aberration is much reduced) have the potential for revolutionizing gamma-ray astronomy. Diffraction-limited lenses of several meters in size are feasible and do not require high technology for their manufacture. Focal lengths are long - up to a million kilometers - but developments in formation flying of spacecraft make possible a mission in which the lens and detector are on two separate spacecraft separated by this distance. A telescope based on these principles can have angular resolution better than a micro second of arc - sufficient to resolve the event horizon of black holes in the nucleii of AGNs. At the same time, the sensitivity can be three orders of magnitude better than that of current instrumentation.

The Burst Alert Telescope (BAT) on Swift has a graded-Z Shield that closes out the volume between the coded aperture mask and the Cadmium-Zinc-Telluride (CZT) detector array. The purpose of the 37-kilogram shield is to attenuate gamma rays that have not penetrated the coded aperture mask of the BAT instrument and are therefore a major source of noise on the detector array. Unlike previous shields made from plates and panels, this shield consists of multiple layers of thin metal foils (lead, tantalum, tin, and copper) that are stitched together much like standard multi-layer insulation blankets. The shield sections are fastened around BAT, forming a curtain around the instrument aperture. Strength tests were performed to validate and improve the design, and the shield will be vibration tested along with BAT in late 2002. Practical aspects such as the layup design, methods of manufacture, and testing of this new kind of graded-Z Shield are presented.