Robert E. McMurray

The Infrared Array Camera (IRAC) for the Spitzer Space Telescope

The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 � m. Two nearly adjacent 5A2 ; 5A2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 � m; 4.5 and 8 � m). All four detector arrays in the camera are 256 ; 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

In-flight performance and calibration of the Infrared Array Camera (IRAC) for the Spitzer Space Telescope

The Infrared Array Camera (IRAC) is one of three focal plane instruments on board the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 μm in two nearly adjacent fields of view. We summarize here the in-flight scientific, technical, and operational performance of IRAC.

Performance of the JWST/MIRI Si:As detectors

The Mid-Infrared Instrument (MIRI) is a 5 to 28 micron imager and spectrometer that is slated to fly aboard the JWST in 2013. Each of the flight arrays is a 1024×1024 pixel Si:As impurity band conductor detector array, developed by Raytheon Vision Systems. JPL, in conjunction with the MIRI science team, has selected the three flight arrays along with their spares. We briefly summarize the development of these devices, then describe the measured performance of the flight arrays along with supplemental data from sister flight-like parts.

Large Format Si:As IBC Array Performance for NGST and Future IR Space Telescope Applications

A mid-infrared(5-30 micron) instrument aboard a cryogenic space telescope can have an enormous impact in resolving key questions in astronomy and cosmology. A space platforms greatly reduced thermal backgrounds (compared to airborne or ground-based platforms), allow for more sensitive observations of dusty young galaxies at high redshifts, star formation of solar-type stars in the local universe, and formation and evolution of planetary disks and systems. The previous generations largest, most sensitive infrared detectors at these wavelengths are 256 x 256 pixel Si:As impurity band conduction devices built by Raytheon Infrared Operations for the SIRTF/IRAC instrument. Raytheon has successfully enhanced these devices, increasing the pixel count by a factor of 16 while matching or exceeding SIRTF/IRAC device performance. NASA-Ames Research Center in collaboration with Raytheon has tested the first high performance large format (1024 x 1024) Si:As IBC arrays for low background applications, such as for the mid-IR instrument on NGST and future IR Explorer missions. These hybrid devices consist of radiation-hard SIRTF/IRAC-type Si:As IBC material mated to a readout multiplexer that has been specially processed for operation at low cryogenic temperatures (below 10 K), yielding high device sensitivity over a wavelength range of 5-28 microns. In this paper, we present laboratory test results from these benchmark devices. Continued development in this technology is essential for conducting large-area surveys of the local and early universe through observation and for complementing future missions such as NGST, TPF, and FIRST.

Transient radiation effects in ultra-low noise HgCdTe IR detector arrays for space-based astronomy

We present measurements of proton-induced single event transients in ultra-low noise HgCdTe IR detector arrays being developed for space-based astronomy and compare to modeling results.

Radiation environment performance of JWST prototype FPAs

As the logical extension of the 20-year mission of the Hubble Space Telescope, NASA plans to launch the James Webb Space Telescope (JWST, formerly NGST) near the end of this decade. As Hubbles scientific and technological successor, equipped with a 6-meter-class deployable mirror, JWST will allow observations of the very early universe and initial formation of galaxies at levels not achievable today. JWSTs unprecedented sensitivity cannot be utilized without a new class of IR focal plane arrays whose performance matches that of the telescope. In particular, JWST focal planes must be able to withstand the ionizing-particle radiation environment expected for its Lagrange-point (L2) orbit and ten-year mission lifetime goal. To help determine their suitability for JWST, NASA is evaluating prototype megapixel-class readouts and hybrid detector arrays under proton bombardment to simulate the anticipated JWST lifetime radiation dose. This report describes the results of early tests on devices from two manufacturers using photovoltaic (HgCdTe or InSb) candidate near-infrared detector structures. Results to date have shown encouraging performance, along with some areas of continuing concern.

Development of Si:As impurity band conduction (IBC) detectors for mid-infrared applications

Si:As Impurity Band Conduction (IBC) detectors offer many significant advantages over other conventional photon detectors utilized for the infrared. SiAs offer excellent spectral response out to 28 μm with dark current in the 0.01e/second range at 7K over a wide bias range with no tunneling limitations. In addition, because of the perfect thermal match between the Si:As IBC detector and the readout IC (ROIC), hybrids formed by mating Si:As IBCs and ROICs are mechanically stable and have no hybrid reliability problems. Since Si:As IBC detectore are fabricated on readily available Si substrates, large formats are realizable. Si:As IBC detectors have been under development since the mid 80s at Raytheon Vision Systems (RVS). Under the NSAS SIRTF program, a 256 x 256 Si:As array was developed and successfully integrated into the SIRTF IRAC instrument. This same array is also utilized in the ASTRO-F IRC instrument. Both missions will be launched shortly and provide a significant improvement in our ability to measure the spectral signatures of solar type stars and galaxies at high redshifts under very low background conditions in space. Under the NASA Origins program, in collaboration with NASA Ames Research Center (ARC), RVS developed a high performance 1024 x 1024 Si:As IBC array. This array was tested at Ames Research Center. This paper will review the progress of Si:As IBC development at RVS, present test data from ARC, and discuss the more recent developments in Si:As IBC detectors for the JWST MIRI instrument and future missions such as SPICA, TPF, FIRST and DARWIN.

Low-noise, low-temperature 256 x 256 Si:As IBC staring FPA

Cryogenic space telescopes such as the Space Infrared Telescope Facility (SIRTF) require large-area focal plane arrays (FPAs) with high sensitivity. Such applications set requirements for the readout arrays to simultaneously provide low noise and low power dissipation at very low temperatures. The Hughes Technology Center (HTC) has developed a low-noise 256 X 256-pixel hybrid FPA composed of a PMOS readout array hybridized to an arsenic- doped silicon (Si:As) impurity-band conduction (IBC) detector which is designed to operate below 10 K. The readout unit cell employs a switched source-follower-per-detector (SFD) design where in signals are multiplexed onto four outputs. The detector was processed using high-purity, multilayered epitaxial processing. The readout was processed using the p-channel subset of HTCs CryoCMOS process.

Variable temperature performance of a Si(Li) detector stack

New experimental data is presented which displays /sup 137/Cs resolution of both single Si(Li) devices and a detector stack 2 cm in height as a function of temperature (85 K/spl les/T/spl les/245 K). We also discuss variations in photopeak shape which indicate that detector charge collection may be temperature dependent over the range of interest. >

Results from a Si(Li) gamma ray detector stack for future Mars missions

The authors present Monte Carlo analysis and experimental data from a novel lithium-drifted silicon detector stack for gamma ray spectroscopy instrumentation in future Mars surface landers and other planetary missions. The Monte Carlo analysis shows full energy photopeaks even in the range of approximately 100 keV to 2 MeV where. in Si, Compton scattering, dominates the absorption processes. Laboratory data are shown for an experimental detector stack of four planar Si(Li) devices, each 5 mm thick with an active area 2 cm in diameter. All the experimental data were collected with maximum temperature of the stack at 175 K. Background reduction was achieved by using the detector of the stack closest to the source in anticoincidence. Experimental data from the stack are compared with the Monte Carlo model for /sup 137/Cs (662 keV). >