This PDF file contains the front matter associated with SPIE Proceedings Volume 7453, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is in its final stages of development. Flying in the stratosphere, SOFIA allows observations throughout the infrared and submillimeter region, with an average transmission of greater than 80%. SOFIA's first generation instrument complement includes high-speed photometers, broadband imagers, moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, and high resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at km/s resolution. These instruments will enable SOFIA to make unique contributions to a broad array of science topics. First science flights will begin in 2010, and the observatory is expected to operate for more than 20 years. The sensitivity, characteristics, science instrument complement, future instrument opportunities and examples of first light science will be discussed.

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is an airborne observatory that will study the universe in the infrared spectrum. A Boeing 747-SP aircraft will carry a 2.5 m telescope designed to make sensitive infrared measurements of a wide range of astronomical objects. In 2008, SOFIA's primary mirror was demounted and coated for the first time. After reintegration into the telescope assembly in the aircraft, the alignment of the telescope optics was repeated and successive functional and performance testing of the fully integrated telescope assembly was completed on the ground. The High-speed Imaging Photometer for Occultations (HIPO) was used as a test instrument for aligning the optics and calibrating and tuning the telescope's pointing and control system in preparation for the first science observations in flight. In this paper, we describe the mirror coating process, the subsequent telescope testing campaigns and present the results.

The EXIST (Energetic X-ray Imaging Survey Telescope) mission includes the 1.1 m optical Infra-Red Telescope (IRT) which provides the capability to locate, identify, and obtain spectra of transient events, in particular GRB afterglows at redshifts up to epoch of reionization. The instrument includes a high spatial resolution imager, low spectral resolution spectrometer (R~ 30) and high resolution slit spectrometer (R~ 3000). This instrument, with the observatory's rapid reaction response will quickly identify the GRB afterglow, measure its brightness curves, redshift, measure spectral characteristics of the afterglows and measure absorption spectra of the intervening intergalactic medium. With this instrument, high redshift GRBs become important tools for studying the growth of structure, observing the processes through which the universe is reionized.

MERTIS (MERcury Thermal infrared Imaging Spectrometer) is an advanced infrared remote sensing instrument that is part of the ESA mission BepiColombo to the planet Mercury. The scientific goals of MERTIS science are surface composition analyses, identification of rock-forming minerals, mapping of the surface mineralogy, and studies of surface temperature variations. MERTIS combines a push-broom IR grating spectrometer (TIS) with a radiometer (TIR), which operate in the wavelength region of 7-14 μm (TIS) and 7-40 μm (TIR), respectively. The instrument represents a modular concept of the sensor head, electronic units and power/calibration systems. The integrated instrument approach allows the subsystems TIS and TIR to share the same optics, instrument electronics and in-fight calibration components. The instrument is designed to achieve a signal-to-noise ratio above 100 in the 7-14 μm wavelength range with a spectral channel width of 90 nm. The TIS optical design combines a three mirror anastigmat (TMA) with a modified Offner spectrometer. The spatial resolution will be about 500 m globally and better than 500 m for 5-10% of the Mercury's surface. With an uncooled microbolometer detector, the instrument can be operated in the hot environment of Mercury without the need for a cryogenic cooling system. We are reporting on the measurement requirements, the status of the instrument development, and ongoing qualification efforts.

MERTIS (MERcury Thermal infrared Imaging Spectrometer) is an advanced infrared remote sensing instrument that is part of the ESA mission BepiColombo to planet Mercury. The enabling technology that allows sending the first spectrometer for the thermal infrared spectral range to Mercury is an uncooled microbolometer. With this detector the instrument can be operated in the hot environment of Mercury without the need of a cryogenic cooling system. The challenge is the calibration of the instrument. A radiometric and a spectroscopic breadboard model of MERTIS were used to develop proper calibration methods and to derive system parameters that support the setup of an end-to-end simulation which can process spectra of planetary analog materials from the DLR Planetary Emissivity Laboratory (PEL) as input signal in order to create a realistic representation of the MERTIS output signal. In the context of the calibration we are reporting on the ongoing efforts to remove the background signal which is contained in the raw image data sets and actually being the dominating signal portion. A background measuring method with using a shutter together with a noise reduction method based on a pixel-by-pixel correlation approach - are discussed and related to the remaining errors of the emissivity spectra which were calculated from raw images of laboratory experiments using onground calibration data sets. The results of the error evaluation and new emissivity spectra from the PEL for high temperatures of planetary analog materials are input parameters for the end-to-end simulation of MERTIS. Regarding the instrument´s SNR a comparison of the simulation results and the experimental data is given and the effect of the noise reduction method.

High resolution images in the Thermal infrared provide a way to detect irrigated fields, to measure evapo-transpiration and detect plant water stress. Models and algorithms have largely improved to yield very good results. However the only in-orbit satellites providing high resolution images in the thermal infrared domain (Landsat, Aster) are long beyond their design lifetime. Furthermore, they do not provide frequent acquisitions (1 image every 16 days for Landsat and Aster, while 1 image per couple of days would be required to monitor plant water stress). There is indeed a need for high resolution and high repetitivity thermal infrared data for hydrological applications. CNES carried out a feasibility study of such a mission on a microsatellite. The mission is called MISTIGRI (MicroSatellite for Thermal InfraRed Ground Surface Imaging). The preliminary payload design was performed by Thales Alenia Space for CNES. An instrumental concept was proposed which fulfils the mission requirements. The study addressed both cooled and uncooled solutions, although a micro-bolometer detector was preferred after trade-off. This paper addresses the results of the MISTIGRI payload feasibility study; it presents the mission requirements, the proposed instrumental concept, describes the major subsystems and provides the preliminary performance budgets.

Aquarius/SAC-D is a cooperative international mission conducted jointly by the National Aeronautics and Space Administration of the United States of America and the Comisión Nacional de Actividades Espaciales of Argentina. Jointly developed by CONAE and the Canadian Space Agency, the New IR Sensor Technology (NIRST) instrument will monitor high temperature events. NIRST has one band in the mid-wave infrared and two bands in the thermal infrared. The baseline design of the NIRST is based on microbolometer technology developed jointly by INO and the CSA. This paper will first present an overview of the design of the NIRST camera module. The manufacturing and qualification activities for the Flight Model will be described and key performance parameters, as measured during the verification campaign, will be reported.

EUMETSAT and ESA initiated in 2000 joint preparatory activities for the formulation and definition of the Meteosat Third Generation (MTG) geostationary system, to ensure continuity and improvement of current Meteosat Second Generation (MSG) services. MTG will become the backbone of the European operational meteorological applications taking the relay from MSG by 2017, and warranting the continuation of the earth imagery mission supported by the Spin Enhanced Visible and Infrared Imager (SEVIRI). The early program definition phases were devoted to the discussion and consolidation of end user requirements and their priorities in meteorology fields as Nowcasting and Very Short Term Weather Forecasting (NWC), Medium/Short Range global and regional Numerical Weather Prediction (NWP), Climate and Air Composition Monitoring and the identification of the relevant observation techniques. In the system conceptualization process, the following missions have been analyzed: • Full Disc High Spectral resolution Imagery (FDHSI) • High Resolution and Fast Imagery (HRFI) • Lightning detection Mission (LI) • IR Sounding Mission (IRS) • UV-VIS-NIR Sounding Mission as a payload complement (UVN). After pre-phase A mission studies (2003-2006), where preliminary instrument concepts were investigated allowing the consolidation of the most critical and demanding technical requirements, phase A studies were launched at the beginning of February (2007-2008) addressing both the space segment system feasibility and ground and operations programmatic aspects. The space segment, phase A level, studies covered the entire suite of optical instruments identified in the preliminary assessments including: 1) a flexible combined imager for both FDHSI and HRFI missions; 2) a Fourier Transform Spectrometer for IRS observations; and 3) a lightning detector sensor. The study of concepts and implementation of the UVN mission are covered by the efforts of ESA and the European Union (EU) in the framework of the Global Monitoring for Environment and Security (GMES) Sentinel 4 program. This paper provides an overview of the outcome of the MTG System analyses at the end of phase A confirming its technical feasibility, the key characteristics of the intended missions, and the progress accomplished in the definition of the satellite optical payloads.

It is well known that the varying geometrical relationships between the Sun and the Earth throughout the year affect to some degree the performance of the instruments onboard Earth orbiting satellites. Following the commissioning of MetOp-A, EUMETSAT and NOAA have continued monitoring the in-orbit performance of AVHRR, HIRS and AMSU-A. The data acquired since the launch of the satellite has allowed studying how the yearly seasonal variations affect the instrument performance.

AIRS was launched on EOS Aqua on May 4, 2002, together with AMSU-A and HSB, to form a next generation polar orbiting infrared and microwave atmospheric sounding system. AIRS is a grating spectrometer with a number of linear arrays of detectors with each detector sensitive to outgoing radiation in a characteristic frequency υ_i with a spectral band pass Δυ_i of roughly υ_i/1200 AIRS contains 2378 spectral channels covering portions of the spectral region 650 cm^-1 (15.38 μm) - 2665 cm^-1 (3.752 μm). These spectral regions contain significant absorption features from two CO₂ absorption bands, the 15 μm (longwave) CO₂ band, and the 4.3 μm (shortwave) CO₂ absorption band. There are also two atmospheric window regions, the 12 μm - 8 μm (longwave) window, and the 4.17 μm - 3.75 μm (shortwave) window. Historically, determination of surface and atmospheric temperatures from satellite observations was performed using primarily observations in the longwave window and CO₂ absorption regions. One reason for this was concerns about the effects, during the day, of reflected sunlight and non-Local Thermodynamic Equilibrium (non-LTE) on the observed radiances in the shortwave portion of the spectrum. According to cloud clearing theory, more accurate soundings of both surface skin and atmospheric temperatures can be obtained under partial cloud cover conditions if one uses the longwave channels to determine cloud cleared radiances R_i for all channels, and uses R_i only from shortwave channels in the determination of surface and atmospheric temperatures. This procedure is now being used by the AIRS Science Team in preparation for the AIRS Version 6 Retrieval Algorithm. This paper describes how the effects on the radiances of solar radiation reflected by clouds and the Earth's surface, and also of non-LTE, are accounted for in the analysis of the data. Results are presented for both daytime and nighttime conditions showing improved surface and atmospheric soundings under partial cloud cover resulted from not using R_i in the retrieval process for any longwave channels sensitive to cloud effects. This improvement is made possible because AIRS NEDT in the shortwave portion of the spectrum is extremely low.

The AIRS Science Team Version 5 retrieval algorithm has been finalized and is now operational at the Goddard DAAC in the processing (and reprocessing) of all AIRS data. The AIRS Science Team Version 5 retrieval algorithm contains two significant improvements over Version 4: 1) Improved physics allows for use of AIRS observations in the entire 4.3 μm CO₂ absorption band in the retrieval of temperature profile T(p) during both day and night. Tropospheric sounding 15 μm CO₂ observations are now used primarily in the generation of cloud cleared radiances R_i. This approach allows for the generation of accurate values of R_i and T(p) under most cloud conditions. 2) Another very significant improvement in Version 5 is the ability to generate accurate case-by-case, level-by-level error estimates for the atmospheric temperature profile, as well as for channel-by-channel error estimates for R_i. These error estimates are used for Quality Control of the retrieved products. We have conducted forecast impact experiments assimilating AIRS temperature profiles with different levels of Quality Control using the NASA GEOS-5 data assimilation system. Assimilation of Quality Controlled T(p) resulted in significantly improved forecast skill compared to that obtained from analyses obtained when all data used operationally by NCEP, except for AIRS data, is assimilated. We also conducted an experiment assimilating AIRS radiances uncontaminated by clouds, as done operationally by ECMWF and NCEP. Forecast resulting from assimilated AIRS radiances were of poorer quality than those obtained assimilating AIRS temperatures.

EarthCARE, the third of ESA's Earth Explorer Core Missions, is aimed at improving the understanding of interactions between clouds, aerosols and radiation - three factors believed to be important in the understanding of global warming. The Broadband Radiometer instrument will serve to confirm the radiated energy estimates which will be derived from the profiles of clouds and aerosols measured by the other instruments on the satellite. The BBR instrument will use 3 arrays of uncooled microbolometers to measure the Top Of the Atmosphere flux in 2 channels (0.2μm - 4μm, 0.2μm - 50μm), simultaneously in 3 directions (nadir, forward and backward). The long wave channel will be inferred from subtraction of the short wave from the total wave measurements. This paper will describe the status of the BBR instrument design, trade-offs and performance. A novel design is required to perform at much higher spatial resolutions than previous Earth Radiation Budget instruments and the method of achieving this will be described.

Ball Aerospace & Technologies Corp. (BATC) has added a powerful capability to its existing imaging spectrometer alignment and test facilities: Scanning Fabry-Perot source filters. These interferometers provide a means for efficient instrument testing with full characterization from the ultra-violet (UV) to longwave infrared (LWIR). Spectral Response Functions (SRF) and geometric distortions are accurately determined with a common approach. The techniques were demonstrated with a two band cryogenic LWIR spectrometer and with the mid-wave infrared (MWIR) Spaceborne InfraRed Atmospheric Sounder for Geosynchronous Earth Orbit (SIRAS-G) laboratory demonstration imaging spectrometer. The spectrometer testing and performance is presented.

We have analyzed photoconductivity in PbSnTe(In) under the action of ~100 ns long terahertz laser pulses with the wavelength 90 - 500 μm in the temperature range 4.2-300 K. Strong photoresponse has been observed at all wavelengths used. Positive persistent photoconductivity is observed at T < 10 K, whereas negative non-persistent photoresponse prevails at higher temperatures T ~ 25 K. Specific features of photoconductivity are discussed.

The feasibility of developing a network of telescopes to monitor the composition of the nighttime atmosphere using stellar spectrophotometry is explored. Spectral measurements of the extinction of starlight by the atmosphere would allow, for instance, quantification of aerosol, cloud, water-vapor, and ozone levels over the full range of elevation and azimuth. These measurements, when combined with data from solar spectrophotometry derived from other instruments, would provide continuous day/night monitoring of the atmospheric composition from the ground. The foundation for such an effort would be a set of stable standard stars with known top-of-the-atmosphere spectral irradiances traceable to international standards based on the SI system of units. Fully automated, reliable, easily maintained and highly costeffective replicas of the spectrophotometric telescope used to calibrate the standard stars can be deployed worldwide at sites such as atmospheric and astronomical observatories.

The spectral irradiance responsivity calibrations of InSb radiometers measured on the tunable-laser based Infrared Spectral Irradiance and Radiance Responsivity Calibration with Uniform Sources (IR-SIRCUS) facility are discussed. This work describes the following changes undertaken to reduce the uncertainties of the calibrations: improve the spatial uniformity, reduce the laser-induced speckle from the gold-coated integrating spheres between 1 μm and 5 μm, improve the stability of the optical parametric oscillator (OPO) tunable laser, reduce the noise from the signal-to-monitor ratio, increase the repeatability of measurements, and reduce the stray light and fringe problems of the radiometer under test. Measurements of the spatial uniformity with the use of polytetrafluoroethylene (PTFE) and gold-coated integrating spheres at different wavelengths have been performed. Different approaches for generating a uniform source, removing the speckle, stabilizing the laser, and improving the signal-to-monitor ratio are also described. The spatial non-uniformity after using these approaches has been shown to be reduced to < 1 %. The uncertainty budget of spectral irradiance responsivity calibrations is discussed, and is found to be mainly due to the measurement repeatability uncertainty component of 1 %. Calibrated radiometers are tested against a source-based scale from the calculated spectral irradiances obtained using a precision aperture and a blackbody (BB) with a known temperature.

The Bidirectional Reflectance Distribution Function (BRDF) has a well defined and studied diffuse measurement standard in the ultraviolet, visible and near infrared (NIR), Spectralon®. It is predictable, stable, repeatable, and has low surface variation because it is a bulk scatterer. In the mid-wave IR (MWIR) and long-wave IR (LWIR), there is not such a well-defined standard. There are well-defined directional hemispherical reflectance (DHR) standards, but the process of integrating BRDF measurements into DHR for the purpose of calibration is problematic at best. Direct BRDF measurement standards are needed. This study systematically investigates the BRDF and its variation for six potential MWIR diffuse BRDF standards. The currently accepted reflectance standard in the MWIR, Infragold®, is compared against two alternative gold-electroplated arc-sprayed aluminum samples, a silver-painted arc-sprayed aluminum sample, a black-paint sample, Spectralon®, and a novel a laser beam diffuser that has been gold coated. Diffuseness is compared by fitting the data to BRDF models, and repeatability is measured by using the standard deviation and percent difference from the mean calculated from multiple BRDF measurements across the surface of the samples.

The wavelength coverage of the IR optical scattering instrument developed at the National Institute of Standards and Technology has been extended to cover the continuous range from 1 μm to 5 μm. Besides the previously available diode lasers at wavelengths of 785 nm, 1.32 μm, and 1.55 μm as well as a line tunable CO₂ lasers from 9.2 μm to 11.2 μm, a PPLN OPO tunable laser is used to generate the desired IR source radiation from 1 μm to 5 μm. We present a brief description of the existing BRDF instrument, as well as the steps required to couple the tunable IR source into the BRDF system, such as improvement of beam profile, polarization control, and sample alignment. The associated results of BRDF measurements for typical specular and diffuse samples are also shown. For specular samples, the BRDF collection aperture size is varied to both 1) resolve the specular component and 2) obtain sufficient signal for the low level diffuse component. The input beam is characterized directly by a pyroelectric sensor array camera in comparison to the BRDF results. The dynamic range of detection, sample alignment, and the averaging of multiple spots for the specular sample measurement are discussed. For diffuse samples, the approach employed for speckle suppression is a combination of translation and rotation averaging. The directional-hemispherical reflectance (DHR) is calculated by integration of the BRDF data, which is found to have good agreement with the DHR results from FTIR integrating sphere measurements.

Wavelength tunable emitters and detectors in the mid-IR wavelength region allow applications including thermal imaging and spectroscopy. Such devices may be realized using a resonant cavity. By mechanically changing the cavity length with MEMS mirror techniques, the wavelengths may be tuned over a considerable range. Vertical external cavity surface emitting lasers (VECSEL) may be applied for gas spectroscopy. Resonant cavity enhanced detectors (RCED) are sensitive at the cavity resonance only. They may be applied for low resolution spectroscopy, and, when arrays of such detectors are realized, as multicolor IR-FPA or IR-AFPA (IR-adaptive focal plane arrays). We review mid-infrared RCEDs and VECSELs using narrow gap IV-VI (lead chalcogenide) materials like PbTe and PbSe as the active medium. IV-VIs are fault tolerant and allow easy wavelength tuning. The VECSELs operate up to above room temperature and emit in the 4 - 5 μm range with a PbSe active layer. RCEDs with PbTe absorbing layers above 200 K operating temperature have higher sensitivities than the theoretical limit for a similar broad-band detector coupled with a passive tunable band-filter.

The Broadband Radiometer (BBR) is an instrument being developed for the ESA EarthCARE satellite. The BBR instrument objective is to provide top-of-atmosphere (TOA) radiance measurements in two spectral channels, and over three along-track directions. The instrument has three fixed telescopes (one for each view) each containing a broadband detector. Each detector consists of an uncooled 30-pixel linear focal plane array (FPA) coated with gold black in order to ensure uniform spectral responsivity from 0.2 μm to 50 μm. The FPA is hybridized with a readout integrated circuit (ROIC) and a proximity electronics circuit-card assembly (CCA) packaged in an aluminum base plate with cover. This paper provides a technical description of the detector design and operation. Performance data at the FPA pixel level as well as unit-level test results on early prototypes of the detectors are also presented.

Use of infrared vision in automotive industry has mainly focused on detection of pedestrians or animals at night or under poor weather conditions. In those approaches, the road infrastructure behavior in infrared range has not been investigated. So, research work was realized using numerical simulations associated with specific experiments in a fog tunnel. The present paper deals with numerical simulations developed for both visible spectrum (visibility in fog) and infrared vision applied to road infrastructure perception in foggy night conditions. Results obtained as a function of fog nature (radiation or advection) are presented and discussed.

The European Extremely Large Telescope will be a large optical/infrared telescope with a segmented primary mirror of 42-m diameter, and 84-m radius of curvature. Each segment, about 1.2-meters across, implies great manufacturing and measuring challenges. To determine the most adequate metrology technique for testing these segments, we report a brief comparative analysis of the four most important testing techniques used for large surfaces. The study shows that the stitching method is the most appropriate technique. We implement a proof of concept to demonstrate the viability of this technique for studying surfaces with a small curvature and estimate the challenges to overcome. The analysis confirms that the success of the stitching technique, in curved elements, ensues because the roughness does not contribute significantly to the surface tendency. Therefore, we propose the use of tendency information to solve Procrustes' problem and to improve the resultant shape of the unified map for surfaces with small curvature, as in the case of the segments of a large primary mirror.

Pulse oximetry technique is a non invasive method useful to monitor the quantity of oxygen in hemoglobin, used in medical diagnosis and clinical decision-making. It is based on the ratio between the red and infrared light absorbance corresponding to the oxygenated (HbO₂) and non-oxygenated (Hb) state of the hemoglobin. We develop the mathematical model to obtain the oxygen saturation value observing that it depends on four known parameters: two transillumination values assessed at the common pulse oximetry wavelengths (λ₁ = 660 nm y λ₂ = 940 nm), and the extinction coefficients for the oxy- and deoxy-hemoglobin at these given wavelengths. Analyzing the extinction curves for oxy- and deoxy-hemoglobin we note that at λ equal to 660 nm the HbO₂ component almost does not contribute to the attenuation of incidance when we transilluminate tissue (7.479x10^-5 cm^-1M^-1). In this case is the Hb component that gives the significant attenuation value (7.863x10^-4 cm^-1M^-1). In 940 nm the extinction coefficient of the Hb is 2.589x10^-5 cm^-1M^-1 and we can ignore it when we count attenuation. At this λ we assume that the pulsate component is only affected by the HbO₂ (2.099x10^-4 cm^-1M^-1). This analysis of hemoglobin extinction coefficients in the absorption curves highlights the signal to noise ratio between these two oxygen dependent elements. We are interested in accentuate the better contrast interval (λ pair), where this signal-to-noise ratio is higher, looking for more transillumination information and more precise SO₂ value. We propose to use a transillumination waveform simulator to study the different effects (respiration, artifact body movement, absorption, low perfusion, etc) presented in complex physiological signals and to know the optical path-integrated behavior when we transilluminate tissue. This is practical for acquisition and processing transillumination signals. The present work is the first part of a λ selection method to guaratee the optimum S/N for measurements in blood using pulse oximetry and spectroscopic techniques at near infrared.

We are developing a system to convert infrared into visible radiation, employing β-diketonate chelate europium (III) thenoyltrifluoroacetonate (EuTTA) as the active medium of conversion. The operational principle of the proposed device is based on the variation of EuTTA fluorescence spectral power and lifetime with temperature. Previously, we characterized the fluorescence properties of the EuTTA in order to achieve IR-to-visible conversion and presented the work performed in order to calibrate our experimental setup. The results showed that a relation between the temperature variations of EuTTA film and those of the impinging IR radiation could be established. However, experimental data exhibited sufficient noise to cause significant errors between the measured and the actual temperature. In this work, we apply a filtering analysis using Fourier theory in order reduce the error in the data, increasing the resolution of our system. After the filtering, the standard deviation in the calculation of fluorescence parameters was reduced and therefore the thermal resolution of our system improved to 0.07 K.

We discuss different arrangements of rotational shearing interferometers intended for the observation of faint companions to nearby stars. Several methods have been proposed for nullifying the radiation of the star to enable the detection planet. One proposal is the rotational shearing interferometer (RSI). The concept of the RSI is based on the idea of comparing a wave front to a rotated version of the wave front. We analyze different previously proposed arrangements of the RSI and find that some represents different instruments.

We propose tissue characterization with ballistic photons, those whose direction or propagation speed is not affected by the presence of tissue. The most critical aspect of the tissue characterization problem is calibration of experimental measurements. The calibration method relates the fringe irradiance (power modulation in one interferometer arm) with the sample concentration under controlled conditions. During this step, the absorption and scattering indices β_a and β_sc are determined as a function of concentration for each material or tissue of interest, using a set of containers to vary travel distance D. It is assumed that linear scattering coefficient, k_sc (absorption coefficient, α_a), is proportional to the number of scattering particles per unit volume, or particle concentration, c, in [ml/l]. Attenuation is proportional to concentration of scattering (absorption) centers and the sample length. The sensitivity of method is estimated at 10^-19 with uncoated plate beam-splitters and intensified photon-counting detector.

We perform a rigorous, diffraction-based analysis to find an analytical expression for the point spread function of the multiple Bracewell interferometric (in-line, even, multi-aperture) configuration, in a single and double embodiment, proposed for extra-solar planet detection. The number of apertures, total length of the linear interferometer array, and the diameter of individual aperture control the shape of this function. The square of the Bessel function modulates the square of the multiple-beam interference term, attenuating it rapidly for off-axis values of the angle.

We analyze the power collection ability of a multiple aperture configuration for geometry where the source and the collector lateral distances are enormously smaller than their separation, as in the case of detection of a nearby planetary system from the Earth or its vicinity. We show that the size, shape, orientation of, or spacing between the individual apertures in a multiple aperture configuration does not impact the amount of power originating at the planet or the star, and therefore does not reduce the signal-to-noise ratio. The collection of power from the star, the planet, and the debris is increased in the same linear fashion by increasing the projected area of all apertures, as by increasing the signal-collection time. In addition, we find that the phase delay between apertures is not of importance. Finally, we demonstrate that no planet is sufficiently close to its star that its image would fall on the zero incidance pattern, according to the laws of Keplerian motion.