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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Low Power Camera-on-a-Chip Using CMOS Active Pixel Sensor Technology

A second generation image sensor technology has been developed at the NASA Jet Propulsion Laboratory as a result of the continuing need to miniaturize space science imaging instruments. Implemented using standard CMOS, the active pixel sensor (APS) technology permits the integration of the detector array with on-chip timing, control and signal chain electronics, including analog-to-digital conversion.

Space Microelectronics Image Sensors APS Digital I↗
NASA NTRS1995

Low Power Camera-on-a-Chip Using CMOS Active Pixel Sensor Technology

A second generation image sensor technology has been developed at the NASA Jet Propulsion Laboratory as a result of the continuing need to miniaturize space science imaging instruments. Implemented using standard CMOS, the active pixel sensor (APS) technology permits the integration of the detector array with on-chip timing, control and signal chain electronics, including analog-to-digital conversion.

Space Microelectronics Image Sensors APS Digital I↗
NASA NTRS1993

Active Pixel Sensors: Are CCD's Dinosaurs?

Charge-coupled devices (CCD's) are presently the technology of choice for most imaging applications. In the 23 years since their invention in 1970, they have evolved to a sophisticated level of performance. However, as with all technologies, we can be certain that they will be supplanted someday. In this paper, the Active Pixel Sensor (APS) technology is explored as a possible successor to the CCD. An active pixel is defined as a detector array technology that has at least one active transistor within the pixel unit cell. The APS eliminates the need for nearly perfect charge transfer -- the Achilles' heel of CCDs. This perfect charge transfer makes CCD's radiation 'soft,' difficult to use under low light conditions, difficult to manufacture in large array sizes, difficult to integrate with on-chip electronics, difficult to use at low temperatures, difficult to use at high frame rates, and difficult to manufacture in non-silicon materials that extend wavelength response.

Fossum, Eric R.↗
NASA NTRS1993

The Atmospheric Infrared Sounder on EOS

Recent breakthroughs in infrared detector array and cryocooler technology have made it possible to convert the concepts of optimum, passive, infrared sounding to a practical satellite-borne instrument.

Atmospheric Infrared Sounder Microwave Humidity So↗
NASA NTRS2006

WFC3 Calibration and Data Processing

Wide Field Camera 3 (WFC3), a panchromatic imager being developed for the Hubble Space Telescope (HST), is now fully integrated and over the past year has completed first rounds of extensive ground testing at Goddard Space Flight Center (GSFC), in both ambient and thermal-vacuum test environments. This report summarizes the results of those tests and describes the pipeline processing methods that will be used to calibrate WFC3 data. WFC3 is designed to ensure that the superb imaging performance of HST is maintained through the end of the mission and takes advantage of recent developments in detector technology to provide new and unique capabilities for HST. WFC3 contains ultraviolet/visible (UVIS) and near-infrared (IR) imaging channels, offering high sensitivity and wide field of view over the broadest wavelength range of any HST instrument. It is slated to replace the current Wide Field and Planetary Camera 2 during Servicing Mission 4. The WFC3 UVIS channel is based on elements from the Advanced Camera for Surveys (ACS)Wide Field Camera (WFC), with a 4096x4096 pixel Marconi CCD covering a 160x160 arcsecond field of view. The WFC3 UVIS channel is optimized for maximum sensitivity in the near-UV and contains a complement of 48 spectral filters and a grism. The WFC3 IR channel uses a 1024x1024 pixel HgCdTe Hawaii-1R detector array covering a 135x135 arcsecond field of view. The array sensitivity is optimized in the 0.8-1.7micron spectral range. The IR channel accomodates 15 filters and 2 grisms for slitless spectroscopy.

Bushouse, H.↗
NASA NTRS2006

The Swift/BAT Hard X-Ray Survey

The BAT instrument on Swift is a wide field (70 deg. '100 deg.) coded aperture instrument with a CdZnTe detector array sensitive to energies of 14-200 keV. Each day, the BAT survey typically covers 60% of the sky to a detection limit of 30 millicrab. BAT makes hard X-ray light curves of similar sensitivity and coverage to the X-ray light curves from XTE/ASM, but in an energy range where sources show remarkably different behavior. Integrating the BAT data produces an all sky map with a source detection limit at 15 months of a few 10(exp -11) ergs per square centimeter per second, depending on the exposure. This is the first uniform all-sky survey at energies high enough to be unaffected by absorption since HEAO 1 in 1977-8. BAT has detected greater than 200 AGN and greater than 180 galactic sources. At high galactic latitudes, the BAT sources are usually easy to identify, but many are heavily absorbed and there are a few quite surprising identifications. The BAT selected galaxies can be used to calculate LogN/LogS and the luminosity function for AGN which are complete and free from common systematics. Several crucial parameters for understanding the cosmic hard x-ray background are now determined.

Tueller, Jack↗
NASA NTRS2006

NASA's Spitzer Space Telescope's Operational Mission Experience

New Generation of Detector Arrays(100 to 10,000 Gain in Capability over Previous Infrared Space Missions). IRAC: 256 x 256 pixel arrays operating at 3.6 microns, 4.5 microns, 5.8 microns, 8.0 microns. MIPS: Photometer with 3 sets of arrays operating at 24 microns, 70 microns and 160 microns. 128 x 128; 32 x 32 and 2 x 20 arrays. Spectrometer with 50-100 micron capabilities. IRS: 4 Array (128x128 pixel) Spectrograph, 4 -40 microns. Warm Launch Architecture: All other Infrared Missions launched with both the telescope and scientific instrument payload within the cryostat or Dewar. Passive cooling used to cool outer shell to approx.40 K. Cryogenic Boil-off then cools telescope to required 5.5K. Earth Trailing Heliocentric Orbit: Increased observing efficiency, simplification of observation planning, removes earth as heat source.

space telescopes↗
NASA NTRS2007

Temperature Evolution in Excitonic Absorptions of Cd(0.96)Zn(0.04) Materials

We report cryogenic optical properties of Cd(0.96)Zn(0.04)Te wafers that are used as substrate seed layers in HgCdTe focal-plane array detectors. These studies are motivated by the fact that the substrate optical properties influence the overall detector performance. The studies consist of measuring the sample frequency dependent transmittance (T) and reflectance (R) above and below the optical band-gap in the UV/Visible and infrared frequency ranges, and with temperature variation of the sample from 5 to 300 K. These measurements show that the optical gap near 1.49 eV at 300 K increases to 1.62 eV at 5 K. Finally, we observe sharp absorption peaks near this gap energy at low temperatures. The close proximity of these peaks to the optical transition threshold suggests that they originate from the creation of bound electron-hole pairs or excitons. The decay of these excitonic absorptions may contribute to a photoluminescence and transient background response of these back-illuminated HgCdTe CCD detectors.

Quijada, Manuel A.↗
NASA NTRS2006

Delta-Doped High Purity Silicon UV-NIR CCDs with High QE and Low Dark Current

Delta doping process was developed on p-channel CCDs for MIDEX-Orion and JDEM/SNAP and was applied to large format (2k x4k) CCDs. Delta doping is applied to fully-fabricated CCDs (complete with Al metallization). High QE and low dark current is demonstrated with delta doped p-channel CCDs. In-house AR coating is demonstrated. Advantages include: Delta doping enables high QE and stability across the entire spectral range attainable with silicon. Delta doping is a low temperature process and is compatible with fully-fabricated detector arrays. Same base device for Orion two channels. High radiation tolerance and no thinning requirements of high purity p-channel. CCDs are additional advantages.

Orion↗
NASA NTRS2001

Apparatus and method using a holographic optical element for converting a spectral distribution to image points

A holographic optical element transforms a spectral distribution of light to image points. The element comprises areas, each of which acts as a separate lens to image the light incident in its area to an image point. Each area contains the recorded hologram of a point source object. The image points can be made to lie in a line in the same focal plane so as to align with a linear array detector. A version of the element has been developed that has concentric equal areas to match the circular fringe pattern of a Fabry-Perot interferometer. The element has high transmission efficiency, and when coupled with high quantum efficiency solid state detectors, provides an efficient photon-collecting detection system. The element may be used as part of the detection system in a direct detection Doppler lidar system or multiple field of view lidar system.

McGill, Matthew J.↗
NASA NTRS1985

Portable instant display and analysis reflectance spectrometer

A portable analysis spectrometer (10) for field mineral identification is coupled to a microprocessor (11) and memory (12) through a bus (13) and A/D converter (14) to display (16) a spectrum of reflected radiation in a band selected by an adjustable band spectrometer (20) and filter (23). A detector array (21) provides output signals at spaced frequencies within the selected spectrometer band which are simultaneously converted to digital form for display. The spectrum displayed is compared with a collection of spectra for known minerals. That collection is stored in memory and selectively displayed with the measured spectrum, or stored in a separate portfolio. In either case, visual comparison is made. Alternatively, the microprocessor may use an algorithm to make the comparisons in search for the best match of the measured spectrum with one of the stored spectra to identify the mineral in the target area.

Goetz, Alexander F. H.↗
NASA NTRS2004

High density pixel array

A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector.

Wiener-Avnear, Eliezer↗
NASA NTRS2003

High density pixel array and laser micro-milling method for fabricating array

A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector.

Wiener-Avnear, Eliezer↗
NASA NTRS2007

Three-dimension imaging lidar

This invention is directed to a 3-dimensional imaging lidar, which utilizes modest power kHz rate lasers, array detectors, photon-counting multi-channel timing receivers, and dual wedge optical scanners with transmitter point-ahead correction to provide contiguous high spatial resolution mapping of surface features including ground, water, man-made objects, vegetation and submerged surfaces from an aircraft or a spacecraft.

Degnan, John J.↗
NASA NTRS1989

Method and apparatus for radiometer star sensing

A method and apparatus for determining the orientation of the optical axis of radiometer instruments mounted on a satellite involves a star sensing technique. The technique makes use of a servo system to orient the scan mirror of the radiometer into the path of a sufficiently bright star such that motion of the satellite will cause the star's light to impinge on the scan mirror and then the visible light detectors of the radiometer. The light impinging on the detectors is converted to an electronic signal whereby, knowing the position of the star relative to appropriate earth coordinates and the time of transition of the star image through the detector array, the orientation of the optical axis of the instrument relative to earth coordinates can be accurately determined.

Wilcox, Jack E.↗
NASA NTRS2007

Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS): Imaging and Tracking Capability

The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 128 detector arrays with a spectral resolution of 0.57/cm with a scan duration of approx. 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept.

Zhou, D. K.↗
NASA NTRS2008

Swift BAT Instrument Thermal Control System Recovery after Spacecraft Safehold in August 2007

The Swift mission Burst Alert Telescope (BAT) Detector Array thermal control system includes two propylene loop heat pipes (LHPs), eight ammonia constant conductance heat pipes (CCHPs), a radiator that has AZ-Tek's AZW-LA-II low alpha white paint, and precision heater controllers that have adjustable set points in flight. The Power Converter Box (PCB) and Image Processor Electronics (IPE) boxes (a primary and a redundant) of the BAT have Z93P white paint radiators. Swift was successfully launched into orbit on November 20, 2004. The spacecraft (S/C) was placed into a safehold mode on August 10, 2007 after an anomaly on inertial reference unit (IRU) #3. It was returned to inertial pointing on August 16 and instrument power up followed. This paper presents a thermal assessment of the BAT instrument thermal control system (TCS) shut down and recovery as a result of the S/C safehold mode. The recovery required starting up the LHPs manually.

Choi, Michael K.↗
NASA NTRS2005

The Spitzer Space Telescope Mission

The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected, and the projected cryogenic lifetime is about five years. Spitzer is thus both a scientific and a technical precursor to the infrared astronomy missions of the future. This very brief paper refers interested readers to several sets of recent publications which describe both the scientific and the technical features of Spitzer in detail. Note that, until 2003 December, Spitzer was known as the Space Infrared Telescope Facility (SIRTF).

space astronomy↗