The Reionization And Transients Infra-Red camera has been built for rapid Gamma-Ray Burst followup and
will provide simultaneous optical and infrared photometric capabilities. The infrared portion of this camera
incorporates two Teledyne HgCdTe HAWAII-2RG detectors, controlled by Teledyne’s SIDECAR ASICs. While
other ground-based systems have used the SIDECAR before, this system also utilizes Teledyne’s JADE2 interface
card and IDE development environment. Together, this setup comprises Teledyne’s Development Kit, which is
a bundled solution that can be efficiently integrated into future ground-based systems. In this presentation, we
characterize the system’s read noise, dark current, and conversion gain.
The Reionization And Transients InfraRed (RATIR) camera has been built for rapid Gamma-Ray Burst (GRB)
followup and will provide quasi-simultaneous imaging in ugriZY JH. The optical component uses two 2048 × 2048
pixel Finger Lakes Imaging ProLine detectors, one optimized for the SDSS u, g, and r bands and one optimized
for the SDSS i band. The infrared portion incorporates two 2048 × 2048 pixel Teledyne HgCdTe HAWAII-2RG
detectors, one with a 1.7-micron cutoff and one with a 2.5-micron cutoff. The infrared detectors are controlled by
Teledyne's SIDECAR (System for Image Digitization Enhancement Control And Retrieval) ASICs (Application
Specific Integrated Circuits). While other ground-based systems have used the SIDECAR before, this system
also utilizes Teledyne's JADE2 (JWST ASIC Drive Electronics) interface card and IDE (Integrated Development
Environment). Here we present a summary of the software developed to interface the RATIR detectors with
Remote Telescope System, 2nd Version (RTS2) software. RTS2 is an integrated open source package for remote
observatory control under the Linux operating system and will autonomously coordinate observatory dome,
telescope pointing, detector, filter wheel, focus stage, and dewar vacuum compressor operations. Where necessary
we have developed custom interfaces between RTS2 and RATIR hardware, most notably for cryogenic focus stage
motor drivers and temperature controllers. All detector and hardware interface software developed for RATIR
is freely available and open source as part of the RTS2 distribution.
In this article we present the mechanical design and the manufacturing of the support structure for the Reionization And
Transients InfraRed (RATIR) camera. The instrument is mounted at the f/13 Cassegrain focus of the 1.5-meter Harold
Johnson telescope of the Observatorio Astronómico Nacional at San Pedro Mártir (OAN/SPM) in Mexico. We describe
the high-level requirements and explain their translation to the mechanical specifications and requirements. We describe
the structural finite-element analysis and the boundary conditions, loads, and general assumptions included in the
simulations. We summarize the expected displacements, rotations and stresses. We present the optomechanical
components and the elements used to attach the instrument to the telescope. Finally, we show the instrument installed on
The Reionization and Transients InfraRed camera (RATIR) is a simultaneous optical/NIR multi-band imaging
camera which is 100% time-dedicated to the followup of Gamma-ray Bursts. The camera is mounted on the
1.5-meter Johnson telescope of the Mexican Observatorio Astronomico Nacional on Sierra San Pedro Martir in
Baja California. With rapid slew capability and autonomous interrupt capabilities, the system will image GRBs
in 6 bands (i, r, Z, Y, J, and H) within minutes of receiving a satellite position, detecting optically faint afterglows
in the NIR and quickly alerting the community to potential GRBs at high redshift (z>6-10). We report here
on this Spring's first light observing campaign with RATIR. We summarize the instrumental characteristics,
capabilities, and observing modes.
The Reionization And Transients Infra-Red (RATIR) camera is intended for robotic operation on the 1.5-meter Harold
Johnson telescope of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
This paper describes the work we have carried out to successfully automate the telescope and prepare it for RATIR. One
novelty is our use of real-time absolute astrometry from the finder telescopes to point and guide the main telescope.
The James Webb Space Telescope (JWST) relies on several innovations to complete its five year mission. One vital
technology is microshutters, the programmable field selectors that enable the Near Infrared Spectrometer (NIRSpec) to
perform multi-object spectroscopy. Mission success depends on acquiring spectra from large numbers of galaxies by
positioning shutter slits over faint targets. Precise selection of faint targets requires field selectors that are both high in
contrast and stable in position. We have developed test facilities to evaluate microshutter contrast and alignment stability
at their 35K operating temperature. These facilities used a novel application of image registration algorithms to obtain
non-contact, sub-micron measurements in cryogenic conditions. The cryogenic motion of the shutters was successfully
characterized. Optical results also demonstrated that shutter contrast far exceeds the NIRSpec requirements. Our test
program has concluded with the delivery of a flight-qualified field selection subsystem to the NIRSpec bench.
The Johns Hopkins University sounding rocket group is entering the final fabrication phase of the Far-ultraviolet Off
Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS); a sounding rocket borne multi-object spectro-telescope
designed to provide spectral coverage of 43 separate targets in the 900 - 1800 Angstrom bandpass over a 30' x 30' field-of-
view. Using "on-the-fly" target acquisition and spectral multiplexing enabled by a GSFC microshutter array, FORTIS
will be capable of observing the brightest regions in the far-UV of nearby low redshift (z ~ 0.002 - 0.02) star forming
galaxies to search for Lyman alpha escape, and to measure the local gas-to-dust ratio. A large area (~ 45 mm x 170 mm)
microchannel plate detector built by Sensor Sciences provides an imaging channel for targeting flanked by two redundant
spectral outrigger channels. The grating is ruled directly onto the secondary mirror to increase efficiency. In this paper, we
discuss the recent progress made in the development and fabrication of FORTIS, as well as the results of early calibration
and characterization of our hardware, including mirror/grating measurements, detector performance, and early operational
tests of the microshutter arrays.
We have developed a high throughput infrared spectrometer for zodiacal light Fraunhofer lines measurements. The instrument is based on a cryogenic dual silicon Fabry-Perot etalon which is designed to achieve high signal to noise Franuhofer line profile measurements. Very large aperture silicon Fabry-Perot etalons wand fast camera optics make these measurements possible. The results of the absorption line profile measurements will provide a model free measure of the zodiacal light intensity in the near infrared. The knowledge of the zodiacal light brightness is crucial for accurate subtraction of zodiacal light foreground for accurate measure of the extragalactic background light after the subtraction of zodiacal light foreground. We present the final design of the instrument and the first results of its performance.
The Johns Hopkins University sounding rocket group is building the Far-ultraviolet Off Rowland-circle Telescope for
Imaging and Spectroscopy (FORTIS), which is a Gregorian telescope with rulings on the secondary mirror. FORTIS will
be launched on a sounding rocket from White Sand Missile Range to study the relationship between Lyman alpha escape
and the local gas-to-dust ratio in star forming galaxies with non-zero redshifts. It is designed to acquire images of a 30'
x 30' field and provide fully redundant "on-the-fly" spectral acquisition of 43 separate targets in the field with a bandpass
of 900 - 1800 Angstroms. FORTIS is an enabling scientific and technical activity for future cutting edge far- and near-uv
survey missions seeking to: search for Lyman continuum radiation leaking from star forming galaxies, determine the
epoch of He II reionization and characterize baryon acoustic oscillations using the Lyman forest. In addition to the high
efficiency "two bounce" dual-order spectro-telescope design, FORTIS incorporates a number of innovative technologies
including: an image dissecting microshutter array developed by GSFC; a large area (~ 45 mm x 170 mm) microchannel
plate detector with central imaging and "outrigger" spectral channels provided by Sensor Sciences; and an autonomous
targeting microprocessor incorporating commercially available field programable gate arrays. We discuss progress to date
in developing our pathfinder instrument.
We are developing a near infrared spectrometer for measuring solar absorption lines in the zodiacal light in the
near infrared region. it has been recently demonstrated1 that observing single Fraunhofer line can be a powerful
tool for extracting zodiacal light parameters based on the measurements of the profile of the Mg I line at 5184 A.
We are extending this technique to the near infrared with the primary goal of measuring the absolute intensity of
the zodiacal light. This measurement will provide the crucial information needed to accurately subtract zodiacal
emission from the DIRBE (Diffuse Infrared Background Experiment) diffuse sky measurements to determine
the intensity of the extragalactic infrared background. The instrument design is based on a dual Fabry-Perot
interferometer with a narrow band filter. Its double etalon design allows to achieve high spectral contrast to
reject the bright out of band atmospheric hydroxyl emission. High spectral contrast is absolutely necessary to
achieve detection limits needed to accurately measure the intensity of the absorption line. We present the design,
the estimated performance of the instrument, and the expected results of the observing program.
Microshutter arrays are one of the novel technologies developed for the James Webb Space Telescope (JWST).
It will allow Near Infrared Spectrometer (NIRSpec) to acquire spectra of hundreds of objects simultaneously
therefore increasing its efficiency tremendously. We have developed these programmable arrays that are based
on Micro-Electro Mechanical Structures (MEMS) technology. The arrays are 2D addressable masks that can
operate in cryogenic environment of JWST. Since the primary JWST science requires acquisition of spectra
of extremely faint objects, it is important to provide very high contrast of the open to closed shutters. This
high contrast is necessary to eliminate any possible contamination and confusion in the acquired spectra by
unwanted objects. We have developed and built a test system for the microshutter array functional and optical
characterization. This system is capable of measuring the contrast of the mciroshutter array both in visible and
infrared light of the NIRSpec wavelength range while the arrays are in their working cryogenic environment. We
have measured contrast ratio of several microshutter arrays and demonstrated that they satisfy and in many
cases far exceed the NIRSpec contrast requirement value of 2000.
One of the James Webb Space Telescope's (JWST) primary science goals is to characterize the epoch of galaxy formation in
the universe and observe the first galaxies and clusters of galaxies. This goal requires multi-band imaging and spectroscopic
data in the near infrared portion of the spectrum for large numbers of very faint galaxies. Because such objects are
sparse on the sky at the JWST resolution, a multi-object spectrograph is necessary to efficiently carry out the required
observations. We have developed a fully programmable array of microshutters that will be used as the field selector
for the multi-object Near Infrared Spectrograph (NIRSpec) on JWST. This device allows apertures to be opened at the
locations of selected galaxies in the field of view while blocking other unwanted light from the sky background and bright
sources. In practice, greater than 100 objects within the field of view can be observed simultaneously. This field selection
capability greatly improves the sensitivity and efficiency of NIRSpec. In this paper, we describe the microshutter arrays,
their development, characteristics, fabrication, testing, and progress toward delivery of a flight-qualified field selection
subsystem to the NIRSpec instrument team.
We have developed microshutter array systems at NASA Goddard Space Flight Center for use as multi-object
aperture arrays for a Near-Infrared Spectrometer (NIRSpec) instrument. The instrument will be carried on the
James Webb Space Telescope (JWST), the next generation of space telescope, after the Hubble Space
Telescope retires. The microshutter arrays (MSAs) are designed for the selective transmission of light from
objected galaxies in space with high efficiency and high contrast. Arrays are close-packed silicon nitride
membranes with a pixel size close to 100x200 μm. Individual shutters are patterned with a torsion flexure
permitting shutters to open 90 degrees with minimized stress concentration. In order to enhance optical
contrast, light shields are made on each shutter to prevent light leak. Shutters are actuated magnetically,
latched and addressed electrostatically. The shutter arrays are fabricated using MEMS bulk-micromachining
and packaged utilizing a novel single-sided indium flip-chip bonding technology. The MSA flight system
consists of a mosaic of 2 x 2 format of four fully addressable 365 x 171 arrays. The system will be placed in
the JWST optical path at the focal plane of NIRSpec detectors. MSAs that we fabricated passed a series of
qualification tests for flight capabilities. We are in the process of making final flight-qualified MSA systems
for the JWST mission.
A complex MEMS device, microshutter array system, is being developed at NASA Goddard Space Flight
Center for use as an aperture array for a Near-Infrared Spectrometer (NirSpec). The instrument will be
carried on the James Webb Space Telescope (JWST), the next generation of space telescope after Hubble
Space Telescope retires. The microshutter arrays (MSAs) are designed for the selective transmission of light
with high efficiency and high contrast. Arrays are close-packed silicon nitride membranes with a pixel size
close to 100x200 &mgr;m. Individual shutters are patterned with a torsion flexure permitting shutters to open 90
degrees with a minimized mechanical stress concentration. Light shields are made on to each shutter for light
leak prevention so to enhance optical contrast. Shutters are actuated magnetically, latched and addressed
electrostatically. The shutter arrays are fabricated using MEMS bulk-micromachining technologies and
packaged using single-sided indium flip-chip bonding technology. The MSA flight concept consists of a
mosaic of 2 x 2 format of four fully addressable 365 x 171 arrays placed in the JWST optical path at the focal
MEMS microshutter arrays (MSAs) are being developed at NASA Goddard Space Flight Center for use as an aperture
array for the Near-Infrared Spectrometer (NirSpec). The instruments will be carried on the James Webb Space
Telescope (JWST), the next generation of space telescope after Hubble Space Telescope retires. The microshutter arrays
are designed for the selective transmission of light with high efficiency and high contrast. Arrays are close-packed
silicon nitride membranes with a pixel size of 105x204 μm. Individual shutters are patterned with a torsion flexure
permitting shutters to open 90 degrees with a minimized mechanical stress concentration. Light shields are made on each
shutter for light leak prevention to enhance optical contrast. Shutters are actuated magnetically, latched and addressed
electrostatically. The shutter arrays are fabricated using MEMS technologies. Single-side indium flip chip bonding is
performed to attach microshutter arrays to substrates.
Micro Electromechanical System (MEMS) microshutter arrays are being developed at NASA Goddard Space Flight Center for use as a field selector of the Near Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST). The microshutter arrays are designed for the spontaneous selection of a large number of objects in the sky and the transmission of light to the NIRSpec detector with high contrast. The JWST environment requires cryogenic operation at 35 K. Microshutter arrays are fabricated out of silicon-on-insulator (SOI) silicon wafers. Arrays are close-packed silicon nitride membranes with a pixel size of 100 x 200 μm. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. Light shields are processed for blocking light from gaps between shutters and frames. The mechanical shutter arrays are fabricated using MEMS technologies. The processing includes multi-layer metal depositions, the patterning of magnetic stripes and shutter electrodes, a reactive ion etching (RIE) to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, followed by a deep RIE (DRIE) back-etch to form mechanical supporting grids and release shutters from the silicon substrate. An additional metal deposition is used to form back electrodes. Shutters are actuated by a magnetic force and latched using an electrostatic force. Optical tests, addressing tests, and life tests are conducted to evaluate the performance and the reliability of microshutter arrays.
The Near Infrared Spectrograph (NIRSpec) for the James Webb Space Telescope (JWST) is a multi-object spectrograph operating in the 0.6-5.0 μm spectral range. One of the primary scientific objectives of this instrument is to measure the number and density evolution of galaxies following the epoch of initial formation. NIRSpec is designed to allow simultaneous observation of a large number of sources, vastly increasing the capability of JWST to carry out its objectives. A critical element of the instrument is the programmable field selector, the Microshutter Array. The system consists of four 175 x 384 close packed arrays of individually operable shutters, each element subtending 0.2” x 0.4”on the sky. This device allows simultaneous selection of over 200 candidates for study over the 3.6’ x 3.6’ field of the NIRSpec, dramatically increasing its efficiency for a wide range of investigations. Here, we describe the development, production, and test of this critical element of the NIRSpec.
We have developed a high resolution near-infrared temperature tunable cryogenic spectrometer with solid Fabry-Perot etalons. It is designed and built for diffuse emission of ionized hydrogen Brγ studies, although with the appropriate pre-filter it can be configured for any near infrared lines. The etalons made from silicon and germanium operate near 77K. The high refractive index of these etalons allows for the construction of a very compact spectrometer. Germanium etalon with 20mm clear aperture is equivalent to a gas spaced Fabry-Perot interferometer of about 80 mm in diameter. A strong temperature dependence of the refractive index for these two materials makes it easy to tune etalons. Combination of these factors allowed to build a compact, high resolution (R=12000) high throughput instrument.
Magnetically actuated MEMS microshutter arrays are being developed at the NASA Goddard Space Flight Center for use in a multi-object spectrometer on the James Webb Space Telescope (JWST), formerly Next Generation Space Telescope (NGST). The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast. The JWST environment requires cryogenic operation at 45K. Microshutter arrays are fabricated out of silicon-on-insulator (SOI) wafers. Arrays consist of close-packed shutters made on silicon nitride (nitride) membranes with a pixel size of 100 × 100 m. Individual shutters are patterned with a torsion flexure permitting shutters to open 90°, with a minimized mechanical stress concentration. Shutters operated this way have survived fatigue life test. The mechanical shutter arrays are fabricated using MEMS technologies. The processing includes a multi-layer metal deposition, patterning of shutter electrodes and magnetic pads, reactive ion etching (RIE) of the front side to form shutters in a nitride film, an anisotropic back-etch for wafer thinning, and a deep RIE (DRIE) back-etch, down to the nitride shutter layer, to form support frames and relieve shutters from the silicon substrate. An additional metal deposition and patterning has recently been developed to form electrodes on the vertical walls of the frame. Shutters are actuated using a magnetic force, and latched electrostatically. One-dimensional addressing has been demonstrated.
SIRTF requires detector arrays with extremely high sensitivity, limited only by the background irradiance. Especially critical is the near infrared spectral region around 3 micrometers , where the detector current due to the zodiacal background is a minimum. IRAC has two near infrared detector channels centered at 3.6 and 4.5 micrometers . We have developed InSb arrays for these channels that operate with dark currents of < 0.2 e/s and multiply-sampled noise of approximately 7 e at 200 s exposure. With these specifications the zodiacal background limited requirements has been easily met. In addition, the detector quantum efficiency of the InSb devices exceeds 90% over the IRAC wavelength range, they are radiation hard, and they exhibit excellent photometric accuracy and stability. Residual images have been minimized. The Raytheon 256 X 256 InSb arrays incorporate a specially developed (for SIRTF) multiplexer and high-grade InSb material.