The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities have been viewed as a first comprehensive assessment of the Observatory's performance and will be used to address the development activity that
is planned for 2012, as well as to identify additional Observatory upgrades. A series of 8 SOFIA Characterization
flights have been conducted from June to December 2011. The HIPO science instrument in
conjunction with the DSI Super Fast Diagnostic Camera (SFDC) have been used to evaluate pointing stability,
including the image motion due to rigid-body and
flexible-body telescope modes as well as possible aero-optical
image motion. We report on recent improvements in pointing stability by using an Active Mass Damper system
installed on Telescope Assembly. Measurements and characterization of the shear layer and cavity seeing, as
well as image quality evaluation as a function of wavelength have been performed using the HIPO+FLITECAM
Science Instrument conguration (FLIPO). A number of additional tests and measurements have targeted basic
Observatory capabilities and requirements including, but not limited to, pointing accuracy, chopper evaluation
and imager sensitivity. This paper reports on the data collected during these
flights and presents current SOFIA
Observatory performance and characterization.
The NIRCam instrument on the James Webb Space Telescope (JWST) will provide a coronagraphic
imaging capability to search for extrasolar planets in the 2 - 5 microns wavelength range. This capability is
realized by a set of Lyot pupil stops with patterns matching the occulting mask located in the JWST
intermediate focal plane in the NIRCam optical system. The complex patterns with transparent apertures
are made by photolithographic process using a metal coating in the opaque region. The optical density
needs to be high for the opaque region, and transmission needs to be high at the aperture. In addition, the
Lyot stop needs to operate under cryogenic conditions. We will report on the Lyot stop design, fabrication
and testing in this paper.
The Bandpass Filters in the NIRCam instrument are required to have high throughput in bandpass spectral region and excellent
out-of-band blocking over the entire region of detector spectral response. The high throughput is needed for the instrument to have high sensitivity for detecting distant galaxies, and the out-of-band
blocking is needed for accurate calibration on James Webb Space Telescope. The operating temperature of the instrument is at cryogenic temperature from 32 Kelvin to 39.5 Kelvin. We have performed spectral measurement of NIRCam bandpass filters at cryogenic temperature after three cryo-to-ambient cycles. We will report the experiment and results in this paper. This work was performed and funded by NASA Goddard Space Flight Center under Prime Contract NAS5-02105.
The NIRCam instrument on the James Webb Space Telescope will provide coronagraphic imaging from λ =1-5 μm of
high contrast sources such as extrasolar planets and circumstellar disks. A Lyot coronagraph with a variety of circular
and wedge-shaped occulting masks and matching Lyot pupil stops will be implemented. The occulters approximate
grayscale transmission profiles using halftone binary patterns comprising wavelength-sized metal dots on anti-reflection
coated sapphire substrates. The mask patterns are being created in the Micro Devices Laboratory at the Jet Propulsion
Laboratory using electron beam lithography. Samples of these occulters have been successfully evaluated in a
coronagraphic testbed. In a separate process, the complex apertures that form the Lyot stops will be deposited onto
optical wedges. The NIRCam coronagraph flight components are expected to be completed this year.
The near-infrared camera (NIRCam) on the James Webb Space Telescope (JWST) will incorporate 2 identical
grisms in each of its 2 long wavelength channels. These transmission gratings have been added to assist with
the coarse phasing of the JWST telescope, but they will also be used for slitless wide-field scientific observations
over selectable regions of the λ = 2.4 − 5.0 μm wavelength range at spectroscopic resolution R ≡ λ/δλ ≃ 2000.
We describe the grism design details and their expected performance in NIRCam. The grisms will provide point-source
continuum sensitivity of approximately AB = 23 mag in 10,000 s exposures with S/N = 5 when binned
to R = 1000. This is approximately a factor of 3 worse than expected for the JWST NIRSpec instrument, but
the NIRCam grisms provide better spatial resolution, better spectrophotometric precision, and complete field
coverage. The grisms will be especially useful for high precision spectrophotometric observations of transiting
exoplanets. We expect that R = 500 spectra of the primary transits and secondary eclipses of Jupiter-sized
exoplanets can be acquired at moderate or high signal-to-noise for stars as faint as M = 10 − 12 mag in 1000 s of
integration time, and even bright stars (V = 5 mag) should be observable without saturation. We also discuss
briefly how these observations will open up new areas of exoplanet science and suggest other unique scientific
applications of the grisms.
The expected stable point spread function, wide field of view, and sensitivity of the NIRCam instrument on the James
Webb Space Telescope (JWST) will allow a simple, classical Lyot coronagraph to detect warm Jovian-mass companions
orbiting young stars within 150 pc as well as cool Jupiters around the nearest low-mass stars. The coronagraph can also
be used to study protostellar and debris disks. At λ = 4.5 μm, where young planets are particularly bright relative to their
stars, and at separations beyond ~0.5 arcseconds, the low space background gives JWST significant advantages over
ground-based telescopes equipped with adaptive optics. We discuss the scientific capabilities of the NIRCam
coronagraph, describe the technical features of the instrument, and present end-to-end simulations of coronagraphic
observations of planets and circumstellar disks.
The Lockheed Martin - University of Arizona Infrared Spectrometer (LAIRS) is designed to image the emission
lines of celestial objects in the 1.3-2.5 μm regime. The Instrument has been built and tested at the Lockheed
Martin Space Systems Advanced Technology Center, and demonstrated to work at cryogenic
temperatures. The Instrument employs a tunable Fabry-Perot Interferometer (FPI) to select the wavelength at
which the Instrument images targets. The FPI employs voice coil actuators and capacitive sensors to maintain
parallelism of its reflective lenses and control their gap spacing. During functional tests of the FPI and the
LAIRS instrument, finesse numbers of 60 and 24 were measured for the interferometer at room temperature
and 80K, respectively. This measurement was performed using a laser operating at 1529.33 nm. This paper
presents an overview of the optical, mechanical, and control design of the FPI, as well as a summary of cryogenic
The Terrestrial Planet Finder Coronagraph (TPF-C) is a deep space mission designed to detect and characterize Earth-like planets around nearby stars. TPF-C will be able to search for signs of life on these planets. TPF-C will use spectroscopy to measure basic properties including the presence of water or oxygen in the atmosphere, powerful signatures in the search for habitable worlds. This capability to characterize planets is what allows TPF-C to transcend other astronomy projects and become an historical endeavor on a par with the discovery voyages of the great navigators.
The CorECam Instrument Concept Study (ICS) addressed the requirements and science program for the
Terrestrial Planet Finder Coronagraph's (TPF-C) primary camera. CorECam provides a simple interface to
TPF-C's Starlight Suppression System (SSS) which would be provided by the TPF-C Program, and
comprises camera modules providing visible, and near-infrared (NIR) camera focal plane imaging. In its
primary operating mode, CorECam will conduct the core science program of TPF-C, detecting terrestrial
planets at visible wavelengths. CorECam additionally provides the imaging capabilities to characterize
terrestrial planets, and conduct an extended science program focused on investigating the nature of the
exosolar systems in which terrestrial planets are detected. In order to evaluate the performance of CorECam
we developed a comprehensive, end-to-end model using OSCAR which has provided a number of key
conclusions on the robustness of the TPF-C baseline design, and allows investigation of alternative
techniques for wavefront sensing and control. CorECam recommends photon counting detectors be
baselined for imaging with TPF-C since they provide mitigations against the background radiation
environment, improved sensitivity and facilitate alternative WFSC approaches.
Relative to ground-based telescopes, the James Webb Space Telescope (JWST) will have a substantial sensitivity advantage in the 2.2-5μm wavelength range where brown dwarfs and hot Jupiters are thought to have significant brightness enhancements. To facilitate high contrast imaging within this band, the Near-Infrared Camera (NIRCAM) will employ a Lyot coronagraph with an array of band-limited image-plane occulting spots. In this paper, we provide the science motivation for high contrast imaging with NIRCAM, comparing its expected performance to that of the Keck, Gemini and 30 m (TMT) telescopes equipped with Adaptive Optics systems of different capabilities. We then describe our design for the NIRCAM coronagraph that enables imaging over the entire sensitivity range of the instrument while providing significant operational flexibility. We describe the various design tradeoffs that were made in consideration of alignment and aberration sensitivities and present contrast performance in the presence of JWST's expected optical aberrations. Finally we show an example of a two-color image subtraction that can provide 10-5 companion sensitivity at sub-arcsecond separations.
The James Webb Space Telescope (JWST) is the scientific successor to both the Hubble Space Telescope and the Spitzer Space Telescope. It is envisioned as a facility-class mission. The instrument suite provides broad wavelength coverage and capabilities aimed at four key science themes: 1)The End of the Dark Ages: First Light and Reionization; 2) The Assembly of Galaxies; 3) The Birth of Stars and Protoplanetary Systems; and 4) Planetary Systems and the Origins of Life. NIRCam is the 0.6 to 5 micron imager for JWST, and it is also the facility wavefront sensor used to keep the primary mirror in alignment.
The NIRCam science objectives are the detection and identification of "first light" objects, the study of star and brown dwarf formation, and the detection and characterization of planetary systems and their formation. These three science programs are also the key objectives of the JWST program as a whole. The NIRCam instrument design is optimized for these objectives within the mission constraints. NIRCam consists of two optics modules, each with a field of view of 2.2 arcmin square. The modules are identical except for the mechanical layout. Each module consists of two channels divided by a dichroic beamsplitter. The short wavelength channel has a band pass of 0.6 - 2.3 microns, with pixels sized for Nyquist sampling of the PSF at 2.0 microns. The long wavelength channel has a band pass of 2.4 - 5.0 microns, with pixels sized for Nyquist sampling at 4.0 microns. Selections of wide (R~4), intermediate (R~10), and narrow (R~100) bandwidth filters are provided in each of the four channels, along with coronagraphic occulting masks and pupil stops. A refractive optical design results in a smaller instrument volume and mass, provides good images at the pupils for wavefront sensing and coronagraphy, allows good access to the pupils and focal planes, and relaxes the alignment requirements compared to a reflective design. The NIRCam instrument is funded by NASA/GSFC under contract NAS5-02105.
The science program for the Next Generation Space Telescope (NGST) relies heavily on a high performance nearinfrared imager. A design which supports the observations outlined in the Design Reference Mission (DRM) and which also supports enhanced searches for "first light" objects and planets has been developed. Key features of the design include use of refractive optics to minimize the volume and mass required, tunable filters for spectroscopic imaging, and redundant imagers for fail-safe wavefront sensing.
Advances in systems engineering, applied sciences, and manufacturing technologies have enabled the development of large ground based and spaced based astronomical instruments having a large Field of View (FOV) to capture a large portion of the universe in a single image. A larger FOV can be accomplished using light weighted optical elements, improved support structures, and the development of mosaic Focal Plane Assemblies (mFPA). A mFPA designed for astronomy can use multiple Charged Coupled Devices (CCD) mounted onto a single camera baseplate integrated at the instrument plane of focus. Examples of current, or proposed, missions utilizing mFPA technology include FAME, GEST, Kepler, GAIA, LSST, and SNAP. The development of a mFPA mandates tighter control on the design trades, component development, CCD characterization, component integration, and performance verification testing. This paper addresses the capability Lockheed Martin Space Systems Company's (LMSSC) Advanced Technology Center (ATC) has developed to perform CCD characterization, mFPA assembly and alignment, and mFPA system level testing.
FAME is a MIDEX astrometry mission designed to map the position of 40,000,000 stars to an accuracy of 50 micro-arc seconds. Optimized between mission requirements, size, weight, and cost, the FAME instrument consists of a 0.6 X 0.5 m2 aperture whose point spread function central peak is linearly sampled by two pixels. To achieve its astrometric mapping mission requirements, this instrument must achieve a single look centroiding accuracy on a visual magnitude 9.0 (or brighter) star of < 0.003 pixels while operating the focal plane in a time domain integration, TDI, mode. As this performance requirement represents a significant improvement over the current state of the art of 0.02 to 0.01 pixel resolution, a risk reduction experiment was conducted to determine our centroiding ability using a flight traceable CCD operated in TDI mode.
The Full-sky Astrometric Mapping Explorer (FAME) is a MIDEX class Explorer mission designed to perform an all-sky, astrometric survey with unprecedented accuracy, determining the positions, parallaxes, proper motions, and photometry of 40 million stars. It will create a rigid, astrometric catalog of stars from an input catalog with 5 < mv < 15. For bright stars, 5 < mv < 9, FAME's goal is to determine positions and parallaxes accurate to < 50 (mu) as, with proper motion errors < 50 (mu) as/year. For fainter stars, 9 < mv < 15, FAME's goal is to determine positions and parallaxes accurate to < 500 (mu) as, with proper motion errors < 500 (mu) as/year. It will also collect photometric data on these 40 million stars in four Sloan DSS colors.
The Medium Resolution Spectrograph (MRS) is a high throughput, versatile, fiber-fed echelle spectrograph for the Hobby-Eberly Telescope (HET). This instrument is designed for a wide range of scientific investigations; it includes single-fiber inputs for the study of point-like sources, synthetic slits of fibers for long slit spectroscopy, multi-fiber inputs for multi- object spectroscopy, and an optical fiber integral field unit. The MRS will have resolution settings between 3500 less than (lambda) /(Delta) (lambda) less than 21000 and will consist of two beams. The initial, visible wavelength beam will have wavelength coverage from 450 - 900 nm in a single exposure. This beam will also have capability in the ranges 390 - 450 and 900 - 950 nm by altering the angles of the echelle and/or cross-disperser gratings. Later, a second beam operating in the near-infrared will be added which will have coverage of 950 - 1300 nm in a single exposure and capability out to 1800 nm. The HET Fiber Instrument Feed (FIF) is mounted at the focal plane of the telescope and positions the fibers feeding the MRS and the High Resolution Spectrograph (HRS). The unique and economical design of the FIF enables the HET's versatility in performing a wide range of scientific investigations with the telescope operating in a queue-scheduled mode.
The optical/UV monitor (OM) on the ESA x-ray cornerstone mission XMM is designed to provide simultaneous optical and UV coverage of x-ray targets viewed by the observatory. The instrument consists of a 30 cm modified Ritchey-Chretien telescope. This feeds a compact photon counting detector operating in the blue part of the optical spectrum and the UV (1600 - 6000 angstrom). The OM has a square field of view of approximately 24 arcmin along the diagonal, and will cover the central region of the field of view of the EPIC x- ray cameras where the x-ray image quality is best. Because of the low sky background in space, the sensitivity of the OM for detecting stars will be comparable to that of a 4-m telescope at the Earth's surface; it should detect a B equals 24th magnitude star in a 1000 s observation using unfiltered light. The pixel size of the detector corresponds to 0.5 arc seconds on the sky in normal operation. In front of each of two redundant detectors are filter wheels containing broad band filters. The filter wheels also contain Grisms for low resolution spectroscopy of brighter sources (lambda/Delta lambda 200) and a 4x field expander which will allow high spatial resolution images of the field center to be taken in optical light.
A multi-national consortium of research groups are developing the XMM (x-ray multi-mirror mission) optical monitor to provide a capability for optical identification and photometry of x-ray sources observed by the XMM observatory. This will be the first multi-wavelength facility dedicated to monitoring the variability of diverse sources from the optical through to x-ray wavelengths. Here we describe the system design and discuss progress in the breadboard phase of the development program.