Glenn Dale, MD, United States
Glenn Dale, MD, United States

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Rauscher B.J.,NASA | Stahle C.,Review-Board | Hill R.J.,Review-Board | Hill R.J.,Conceptual Analytics LLC | And 37 more authors.
AIP Advances | Year: 2012

The JamesWebb Space Telescope (JWST) is the successor to the Hubble Space Telescope. JWST will be an infrared-optimized telescope, with an approximately 6.5 m diameter primary mirror, that is located at the Sun-Earth L2 Lagrange point. Three of JWST's four science instruments use Teledyne HgCdTe HAWAII-2RG (H2RG) near infrared detector arrays. During 2010, the JWST Project noticed that a few of its 5 ìm cutoff H2RG detectors were degrading during room temperature storage, and NASA chartered a "Detector Degradation Failure Review Board" (DD-FRB) to investigate. The DD-FRB determined that the root cause was a design flaw that allowed indium to interdiffuse with the gold contacts and migrate into the HgCdTe detector layer. Fortunately, Teledyne already had an improved design that eliminated this degradation mechanism. During early 2012, the improved H2RG design was qualified for flight and JWST began making additional H2RGs. In this article, we present the two public DD-FRB "Executive Summaries" that: (1) determined the root cause of the detector degradation and (2) defined tests to determine whether the existing detectors are qualified for flight.We supplement these with a brief introduction to H2RG detector arrays, some recent measurements showing that the performance of the improved design meets JWST requirements, and a discussion of how the JWST Project is using cryogenic storage to retard the degradation rate of the existing flight spare H2RGs. Copyright © 2012 Author(s).


Rauscher B.J.,Global Science and Technology | Antonille S.R.,Global Science and Technology | Boehm N.,Global Science and Technology | Davila P.S.,Conceptual Analytics LLC | And 10 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2013

We describe the "overlight" test that was done for JWST's Teledyne H2RG HgCdTe near-infrared detector arrays. We projected many very bright λ = 632.8 nm spots onto one flight representative, substrate-removed, HgCdTe 5 μm cutoff detector array. We allowed individual spots to "burn in" for as long as ≈1000 s before turning off the laser. We did not detect any permanent change in detector performance for extreme over illuminations as bright as 320 μW pixel-1 (≤ 1 μW μm-2) after the array had been returned to ambient laboratory temperature and pressure. The brightest individual spot contained roughly 4 mW of power spread over a 100 μm diameter circular area. This is brighter than the brightest lasers that are planned for use during JWST integration and testing. It is also ≈103× brighter than any 632.8 nm astronomical source in the night sky. © 2013. The Astronomical Society of the Pacific. All rights reserved.


Gong Q.,NASA | Content D.A.,NASA | Dominguez M.,NASA | Emmett T.,NASA | And 7 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

The slitless spectrometer plays an important role in the WFIRST mission for the survey of emission-line galaxies. This will be an unprecedented very wide field, HST quality 3D survey of emission line galaxies1. The concept of the compound grism as a slitless spectrometer has been presented previously. The presentation briefly discusses the challenges and solutions of the optical design, and recent specification updates, as well as a brief comparison between the prototype and the latest design. However, the emphasis of this paper is the progress of the grism prototype: The fabrication and test of the complicated diffractive optical elements and powered prism, as well as grism assembly alignment and testing. Especially how to use different tools and methods, such as IR phase shift and wavelength shift interferometry, to complete the element and assembly tests. The paper also presents very encouraging results from recent element tests to assembly tests. Finally we briefly touch the path forward plan to test the spectral characteristic, such as spectral resolution and response. © 2016 SPIE.


Smith B.,Stargazer Systems Inc. | Loose M.,Markury Scientific Inc. | Alkire G.,Stargazer Systems Inc. | Joshi A.,SAAZ Micro Inc. | And 10 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

The Wide-Field Infrared Survey Telescope (WFIRST) will have the largest near-IR focal plane ever flown by NASA, a total of 18 4K x 4K devices. The project has adopted a system-level approach to detector control and data acquisition where 1) control and processing intelligence is pushed into components closer to the detector to maximize signal integrity, 2) functions are performed at the highest allowable temperatures, and 3) the electronics are designed to ensure that the intrinsic detector noise is the limiting factor for system performance. For WFIRST, the detector arrays operate at 90 to 100 K, the detector control and data acquisition functions are performed by a custom ASIC at 150 to 180 K, and the main data processing electronics are at the ambient temperature of the spacecraft, notionally ∼300 K. The new ASIC is the main interface between the cryogenic detectors and the warm instrument electronics. Its single-chip design provides basic clocking for most types of hybrid detectors with CMOS ROICs. It includes a flexible but simple-To-program sequencer, with the option of microprocessor control for more elaborate readout schemes that may be data-dependent. All analog biases, digital clocks, and analog-To-digital conversion functions are incorporated and are connected to the nearby detectors with a short cable that can provide thermal isolation. The interface to the warm electronics is simple and robust through multiple LVDS channels. It also includes features that support parallel operation of multiple ASICs to control detectors that may have more capability or requirements than can be supported by a single chip. © 2016 SPIE.


Rossetti D.,Conceptual Analytics LLC | Rossetti D.,NASA | Keer B.,NASA | Panek J.,NASA | And 4 more authors.
AIAA SPACE 2015 Conference and Exposition | Year: 2015

Satellite servicing has been a proven capability of NASA since the first servicing missions in the 1980s with astronauts on the space shuttle. This capability enabled the on-orbit assembly of the International Space Station (ISS) and saved the Hubble Space Telescope (HST) mission following the discovery of the flawed primary mirror. The effectiveness and scope of servicing opportunities, especially using robotic servicers, is a function of how cooperative a spacecraft is. In this paper, modularity will be presented as a critical design aspect for a spacecraft that is cooperative from a servicing perspective. Different features of modularity are discussed using examples from HST and the Multimission Modular Spacecraft (MMS) program from the 1980s and 1990s. The benefits of modularity will be presented including those directly related to servicing and those outside of servicing including reduced costs and increased flexibility. The new Reconfigurable Operational spacecraft for Science and Exploration (ROSE) concept is introduced as an affordable implementation of modularity that provides cost savings and flexibility. Key aspects of the ROSE architecture are discussed such as the module design and the distributed avionics architecture. The ROSE concept builds on the experience from MMS and due to its modularity, would be highly suitable as a future client for on-orbit servicing. © 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved.


Hill R.J.,Conceptual Analytics Inc. | Malumuth E.,Wyle | Foltz R.,NASA | Kimble R.A.,NASA | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The Detector Characterization Laboratory at NASA/GSFC has investigated the reciprocity failure characteristics of 1.7μm cut-off HgCdTe devices provided by Teledyne Imaging Sensors to the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) project. The reciprocity failure follows a power law behavior over the range of fluxes tested (0.1-10 4 photons/second). The slope of the power law varies among detectors, ranging from ~0.3-1%/dex at 1.0μm, which is much smaller than the ~6%/dex effect observed with the HST NICMOS 2.5μm cut-off detectors. In addition, the reciprocity failure exhibits no wavelength dependence, although only a restricted range of wavelengths (0.85-1.0μm) has been explored to date. Despite its relatively small magnitude, reciprocity failure is nevertheless an important effect in the calibration of WFC3 data, as well as in other applications in which there is a large difference in flux between the photometric standards and the scientific sources of interest. © 2010 SPIE.


Rauscher B.J.,NASA | Boehm N.,Global Science & Technology, Inc. | Cagiano S.,NASA | Delo G.S.,Global Science & Technology, Inc. | And 9 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2014

ESA and NASA recently selected two 5 μm cutoff Teledyne H2RG sensor chip assemblies (SCA) for flight on the James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec). These HgCdTe SCAs incorporate Teledyne’s “improved barrier layer” design that eliminates the degradation that affected earlier JWST H2RGs. The better indium barrier, together with other design changes that Teledyne phased in from other programs over the years, has improved the performance and reliability of JWST’s SCAs. In this article, we describe the measured performance characteristics that most directly affect scientific observations including read noise, total noise, dark current, quantum efficiency (QE), and image persistence. As part of measuring QE, we inferred the quantum yield over the full NIRSpec pass band of λ = 0:6−5 μm and found that it exceeds unity for photon energies Eγ > (2:65 ±.2)Eg, where Eg is the HgCdTe bandgap energy. This corresponds to λ ≲ 2 μm for NIRSpec’s 5 μm cutoff HgCdTe. © 2014. The Astronomical Society of the Pacific. All rights reserved.

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