NESSI: the New Mexico Tech Extra(solar)planet Spectroscopic Survey Instrument is a ground-based multi-object
spectrograph that operates in the near-infrared and is being deployed this fall at the Magdalena Ridge Observatory 2.4 m
telescope. When completed later this year, it is expected to be used to characterize the atmospheres of transiting
exoplanets with unprecedented ground-based accuracies down to about K = 9 magnitude. The superior capabilities of
NEESI for this type of work lay, in part, in the design philosophy used for the instrument which is well-focused on the
exoplanet case. We report here on this design philosophy, detail and status of the design and assembly, and preparation
for first light in the fall of 2012.
NESSI: the New Mexico Tech Extrasolar Spectroscopic Survey Instrument is a ground-based multi-object
spectrograph that operates in the near-infrared. It will be installed on one of the Nasmyth ports of the
Magdalena Ridge Observatory (MRO) 2.4-meter Telescope. NESSI operates stationary to the telescope
fork so as not to produce differential flexure between internal opto-mechanical components during or
between observations. In this paper we report on NESSI's detailed mechanical and opto-mechanical design,
and the planning for mechanical construction, assembly, integration and verification.
Recently, the Keck interferometer was upgraded to do self-phase-referencing (SPR) assisted K-band spectroscopy at R ~ 2000. This means, combining a spectral resolution of 150 km/s with an angular resolution of 2.7 mas, while maintaining
high sensitiviy. This SPR mode operates two fringe trackers in parallel, and explores several infrastructural requirements
for off-axis phase-referencing, as currently being implemented as the KI-ASTRA project. The technology of self-phasereferencing
opens the way to reach very high spectral resolution in near-infrared interferometry. We present the scientific
capabilities of the KI-SPR mode in detail, at the example of observations of the Be-star 48 Lib. Several spectral lines of the
cirumstellar disk are resolved. We describe the first detection of Pfund-lines in an interferometric spectrum of a Be star, in
addition to Br γ. The differential phase signal can be used to (i) distinguish circum-stellar line emission from the star, (ii) to directly measure line asymmetries tracing an asymetric gas density distribution, (iii) to reach a differential, astrometric
precision beyond single-telescope limits sufficient for studying the radial disk structure. Our data support the existence of
a radius-dependent disk density perturbation, typically used to explain slow variations of Be-disk hydrogen line profiles.
ASTRA (ASTrometric and phase-Referencing Astronomy) is an upgrade to the existing Keck Interferometer
which aims at providing new self-phase referencing (high spectral resolution observation of YSOs), dual-field
phase referencing (sensitive AGN observations), and astrometric (known exoplanetary systems characterization
and galactic center general relativity in strong field regime) capabilities. With the first high spectral resolution
mode now offered to the community, this contribution focuses on the progress of the dual field and astrometric modes.
The Keck Interferometer (KI) combines the two 10m diameter Keck telescopes providing milliarcsecond angular
resolution. KI has unique observing capabilities such as sensitive K-band V2, L-band V2 and N-band nulling operations. The instrument status of the Keck Interferometer since the last SPIE meeting in 2008 is summarized. We discuss the
performance of new visibility observing capabilities including L-band and self-phase referencing modes. A simultaneous
dual-beam-combiner mode in the K and L-band has been demonstrated, nearly doubling operational efficiency for bright
targets. Operational improvements including simplified reliable operations with reduced personnel resources are
highlighted. We conclude with a brief review of the current and future developmental activities of KI. Details of ASTRA
developments, nulling performance and science results are presented elsewhere at this conference.
The Keck Interferometer combines the two 10 m Keck telescopes as a long baseline interferometer, funded by
NASA, as a joint development among the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the
Michelson Science Center. Since 2004, it has offered an H- and K-band fringe visibility mode through the Keck
TAC process. Recently this mode has been upgraded with the addition of a grism for higher spectral resolution.
The 10 um nulling mode, for which first nulling data were collected in 2005, completed the bulk of its engineering
development in 2007. At the end of 2007, three teams were chosen in response to a nuller key science call to
perform a survey of nearby stars for exozodiacal dust. This key science observation program began in Feb. 2008.
Under NSF funding, Keck Observatory is leading development of ASTRA, a project to add dual-star capability for
high sensitivity observations and dual-star astrometry. We review recent activity at the Keck Interferometer, with an
emphasis on the nuller development.
The Keck Interferometer combines the two 10m diameter Keck telescopes for near-infrared fringe visibility, and mid-infrared
nulling observations. We report on recent progress with an emphasis on new visibility observing capabilities,
operations improvements for visibility and nulling, and on recent visibility science. New visibility observing capabilities
include a grism spectrometer for higher spectral resolution. Recent improvements include a new AO output dichroic for
increased infrared light throughput, and the installation of new wave-front controllers on both Keck telescopes. We also
report on recent visibility results in several areas including (1) young stars and their circumstellar disks, (2) pre-main
sequence star masses, and (3) Circumstellar environment of evolved stars. Details on nuller instrument and nuller science
results, and the ASTRA phase referencing and astrometry upgrade, are presented in more detail elsewhere in this
conference.
The Keck interferometer has its V2 science mode open to its astronomical community and the Nuller science mode is
maturing in its development. In order to push on and improve the limits of the instrument a program of analyzing the
characteristics of its beamlines has begun. The purpose of this endeavor is to understand beamtrain characteristics for
assessing and improving overall system performance. In this paper we present some of the initial results from
measurements as well as preliminary analyses of polarization and wavefront quality. Polarization measurements were
made on the internal beamtrains for two orthogonal telescope azimuth positions. The wavefront test is a static beamline
measurement using a Shack-Hartmann sensor to sample the wavefront quality of the beamtrain. Also results from a
dynamic beamtrain monitoring scheme is presented that involves measurements from the angle tracking system during
on-sky operation.
The Keck Interferometer Nuller (KIN) is now largely in place at the Keck Observatory, and functionalities and
performance are increasing with time. The main goal of the KIN is to examine nearby stars for the presence of exozodiacal
emission, but other sources of circumstellar emission, such as disks around young stars, and hot exoplanets are
also potential targets. To observe with the KIN in nulling mode, knowledge of the intrinsic source spectrum is essential,
because of the wide variety of wavelengths involved in the various control loops - the AO system operates at visible
wavelengths, the pointing loops use the J-band, the high-speed fringe tracker operates in the K-band, and the nulling
observations take place in the N-band. Thus, brightness constraints apply at all of these wavelengths. In addition, source
structure plays a role at both K-band and N-band, through the visibility. In this talk, the operation of the KIN is first
briefly described, and then the sensitivity and performance of the KIN is summarized, with the aim of presenting an
overview of the parameter space accessible to the nuller. Finally, some of the initial observations obtained with the KIN
are described.
In this paper we report on progress at the Keck Interferometer since the 2004 SPIE meeting with an emphasis on the operations improvements for visibility science.
The Keck Interferometer Nuller (KIN) will be used to examine nearby stellar systems for the presence of circumstellar exozodiacal emission. A successful pre-ship review was held for the KIN in June 2004, after which the KIN was shipped to the Keck Observatory. The integration of the KIN's many sub-systems on the summit of Mauna Kea, and initial on-sky testing of the system, has occupied the better part of the past year. This paper describes the KIN system-level configuration, from both the hardware and control points of view, as well as the current state of integration of the system and the measurement approach to be used. During the most recent on-sky engineering runs in May and July 2005, all of the sub-systems necessary to measure a narrowband null were installed and operational, and the full nulling measurement cycle was carried out on a star for the first time.
One of the science goals of NASA's Navigator program is ground-based narrow-angle astrometry for extra-solar planet detection, which could be done as part of the proposed Outrigger Telescopes Project. The narrow-angle measurement process, which would use the outrigger telescopes, starts with the determination of the conventional interferometer astrometric baseline, determined from wide-angle astrometry of Hipparcos stars. A baseline monitor system would be employed at each outrigger telescope. This system monitors the pivot point of each telescope - the end point of the astrometric baseline - to measure telescope imperfections that would cause the baseline to vary with telescope rotation. The baseline monitor includes azimuth and elevation cameras that monitor runout along the azimuth and elevation axes of the telescopes. In conjunction with the baseline monitor system, a pivot monitor camera in the dual-star module is used to register the laser metrology corner-cube reflector to the telescope pivot, tying the narrow-angle baseline, which applies to the narrow-angle astrometric measurement, to the wide-angle baseline. In this paper we present the proposed designs for the baseline monitor and pivot-point camera.
The Keck Interferometer includes an autoalignment system consisting of pop-up targets located at strategic locations along the beam trains of each arm of the instrument along with a sensor and control system. We briefly describe the hardware of the system and then proceed to a description of the two operational modes of the system. These are: 1) to provide an initial alignment of the coude paths in each arm, and 2) to recover coude alignments between changes of the static delay sled positions. For the initial alignment mode, we review the system performance requirements along with the software used for image acquisition and centroiding. For coudé alignment recovery, we describe beam-train surveys through the static delay (Long Delay Line) and criteria for a successful recovery of a coudé alignment. Finally, we describe the results of testing of the autoalignment system.
The visibility science mode of the Keck Interferometer fully transitioned into operations with the successful completion of its operational readiness review in April 2004. The goal of this paper is to describe this science mode and the operations structure that supports it.
The NASA Outrigger Telescope Project is a ground-based component of NASA's Navigator Program. The proposed project would utilize four to six 1.8-meter telescopes with co-rotating domes configured as an interferometer. One of the project’s scientific goals is the detection of exoplanets, which would be accomplished with long baseline narrow-angle astrometry. This astrometry mode would be able to detect Uranus mass planets up to 60 light years away. The requirements of narrow-angle astrometry, both technically and operationally, levy requirements on the telescopes and enclosures, including, for example, wavefront quality, pivot stability, and slew speed. This paper will describe these requirements and how they were achieved in the design. It will also discuss the testing and verification of these requirements. Actual telescope performance as tested at EOS Technologies is presented elsewhere in these proceedings.
The W.M. Keck Observatory is conducting a focused effort to identify and mitigate facility vibrations that significantly affect optimal optical performance. This effort should improve the performance of both Keck adaptive optics systems, the laser guide star, the AO instruments, and the interferometer, and will benefit future high precision instruments.
We present our strategy for mitigating vibrations in a large ground-based telescope. Our approach is to establish reasonable confidence in identifying the facility vibration sources that most significantly deteriorate optical performance. For the interferometer we completed vibration surveys that correlate vibrations on the interferometer beam path with direct vibration measurements on the telescope structure and facility. We developed a metric to evaluate the effect of vibrations on the entire interferometer beamline. From our surveys, we prioritized facility components to be addressed, and developed approaches to mitigate key vibrations contributions. Initial results show large local improvements, and global improvements to our vibration environment.
The Keck Interferometer is entering a regular limited observational phase. A restricted number of observers are expected to use the instrument over the course of the next few years in a shared-risk capacity. To facilitate this, the W. M. Keck Observatory and the Jet Propulsion Laboratory are following a Handover procedure consisting of a number of stages related to the science modes of the instrument as they reach completion. The first of these is the Visibility Science mode that involves only the two Keck telescopes. Other modes to follow are Nulling, Differential Phase, Astrometry, and Imaging. The process includes defining a reasonable level of functionality of each mode, training observatory staff to maintain and schedule tasks related to the upkeep of each mode, and defining and documenting each of the subsystems related to each mode. Here we discuss the outline of the Handover plan and report on its progress to date.
KEYWORDS: Near field, Prisms, Near field optics, Near field scanning optical microscopy, Electromagnetism, Reflection, Optical microscopy, Dielectrics, Magnetism, Microscopy
In this paper we present a simplified but general theoretical model of the interaction of a near- field probe with evanescent fields. The predicted behavior exhibits some interesting features. We also describe an experiment to test these models and report our first results.
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