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NASA NTRS1992

Cryogenic measurements of aerojet GaAs n-JFETs

The spectral noise characteristics of Aerojet GaAs n-JFETs have been investigated down to liquid helium temperatures. Voltage noise characterization was performed with the FET in 1) the floating gate mode, 2) the grounded gate mode to determine the lowest noise readings possible and 3) with an extrinsic silicon photodetector at various detector bias voltages, to determine optimum operating conditions. Current noise characterization was measured at the drain in the temperature range 300 to 77 K. Device design and MBE processing are described. Static I-V characterization is done at 300, 77 and 6 K. The measurements indicate that the Aerojet GaAs n-JFET is a quiet and stable device at liquid helium temperatures. Hence, it can be considered as a readout line driver or infrared detector preamplifier as well as a host of other cryogenic applications. Its noise performance is superior to that of Si MOSFETs operating at liquid helium temperatures, and is equal to the best Si n-JFETs operating at 300 K.

Goebel, John H.↗

NASA NTRS1983

Low background IR detector and detector array evaluations

A technology program has been underway at Ames since 1978 to develop and evaluate detectors and integrated detector arrays for low-background astronomical applications. The approach is to evaluate existing (less than 24 micron) array technology under low-background conditions, with the aim of adapting and optimizing existing devices. For longer wavelengths, where the technology is much less mature, development is sponsored and devices are evaluated, in both discrete and array formats, for eventual applications. The status of this program has been reported previously. We rely on industrial and university sources for the detectors. Typically, after a brief functionality check in the supplier's laboratory, we work with the device at Ames to characterize its low-background performance. In the case of promising arrays or detectors, we conduct ground-based telescope testing to face the problems associated with real applications. A list of devices tested at Ames is given. In the array category, accumulation-mode charge-injection-devices (AMCIDs) appear repeatedly; this reflects our recent experience with the 2 x 64 and 16 x 16 arrays. Results from the 1 x 16 CID and InSb CCD have been reported. The status of our tests of the discrete Ge:x detectors from Lawrence Berkeley Laboratory are described below. Tests of a 1 x 2 switched sample photoconductor array are just beginning. A 32-channel CMOS multiplexer has been tested at 10 K. Low-temperature silicon MOSFETs and germanium JFETs have also been tested, primarily at Ball Aerospace. This paper describes results to date on three elements of this program: AMCID array, discrete Ge:Ga detectors, and Ge JFET preamplifiers.

Goebel, J. H.↗

NASA NTRS1983

A mosaic infrared sensor for space astronomy

The objectives were to give a theoretical and/or experimental evaluation of HgCdTe detector arrays (1 to 5 micron) for space astronomy applications; to analyze low background HgCdTe/CCD coupling schemes for low temperature space astronomy; and to test and evaluate existing silicon CCDs at temperatures below 77 K. The accomplishments are the theoretical tradeoffs for PV-HgCdTe detectors completed at low temperatures; the characterization of existing PV-HgCdTe detector arrays (1 to 5 Micron) at low temperatures (low temperature performance exceeds measurement capability, preamplifier designed and built, and limiting detector current mechanisms analyzed); various detector/CCD coupling approaches were evaluated (resettable gate coupled approach chosen for low background); and low temperature CCD performance at 50 K shows compatibility with astronomical requirements.

Sood, Ashok K.↗

NASA NTRS1994

System Measures Thermal Noise In A Microphone

Vacuum provides acoustic isolation from environment. System for measuring thermal noise of microphone and its preamplifier eliminates some sources of error found in older systems. Includes isolation vessel and exterior suspension, acting together, enables measurement of thermal noise under realistic conditions while providing superior vibrational and accoustical isolation. System yields more accurate measurements of thermal noise.

Zuckerwar, Allan J.↗

NASA NTRS1992

X-ray spectroscopy with silicon pin and avalanche photo diodes

Results of an evaluation of silicon P-Intrinsic-N (PIN) photodiodes and Avalanche Photodiodes (APD) for the direct detection of soft x rays from 1 to 20 keV and for the detection of scintillation light output from CsI(TI) for higher x ray energies (30 to 1000 keV) are presented. About one keV resolution was achieved at room temperature for both the PIN and APD detectors for soft x rays (1 to 20 keV). Commercially available, low power (18 mV), low noise, hybrid preamplifiers, were used. These photodiodes were also coupled to CsI(TI) scintillator and obtained about 6 resolution at 662 keV. The photodiode frequency response matches well with the emission spectrum of the CsI(TI) scintillator providing good spectral resolution and a higher signal than NaI(TI) when viewed by conventional photomultipliers. A PIN-CsI(TI) combination provides a low energy threshold of around 60 keV while for the APD-CsI(TI) it is 15 keV.

Desai, U. D.↗

NASA NTRS1993

Cryogenic measurements of aerojet GaAs n-JFETs

The spectral noise characteristics of Aerojet gallium arsenide (GaAs) junction field effect transistors (JFET's) have been investigated down to liquid-helium temperatures. Noise characterization was performed with the field effect transistor (FET) in the floating-gate mode, in the grounded-gate mode to determine the lowest noise readings possible, and with an extrinsic silicon photodetector at various detector bias voltages to determine optimum operating conditions. The measurements indicate that the Aerojet GaAs JFET is a quiet and stable device at liquid helium temperatures. Hence, it can be considered a readout line driver or infrared detector preamplifier as well as a host of other cryogenic applications. Its noise performance is superior to silicon (Si) metal oxide semiconductor field effect transistor (MOSFET's) operating at liquid helium temperatures, and is equal to the best Si n channel junction field effect transistor (n-JFET's) operating at 300 K.

Goebel, John H.↗

NASA NTRS1994

Influence of an externally modulated photonic link on a microwave communications system

We analyze the influence of an externally modulated photonic link on the performance of a microwave communications system. From the analysis, we deduce limitations on the photocurrent, magnitude of the relaxation oscillation noise of the laser, third-order intercept point of the preamplifier, and other parameters in order for the photonic link to function according to the system specifications. Based on this, we outline a procedure for designing a photonic link that can be integrated in a system with minimal performance degradation.

Yao, X. S.↗

NASA NTRS1994

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

This interim report consists of two reports: 'Space Radiation Effects on Si APDs for GLAS' and 'Computer Simulation of Avalanche Photodiode and Preamplifier Output for Laser Altimeters.' The former contains a detailed description of our proton radiation test of Si APD's performed at the Brookhaven National Laboratory. The latter documents the computer program subroutines which were written for the upgrade of NASA's GLAS simulator.

Davidson, Frederic M.↗

NASA NTRS1995

The Yerkes Observatory 60-channel far infrared camera for the Kuiper Airborne Observatory

The Yerkes Observatory Far Infrared Camera employs a two-dimensional, 60-detector array of (3)He-cooled silicon bolometers for broadband imaging in the spectral range of 40 to 240 microns. Four interchangeable filters have effective wavelengths of 60, 100, 160, and 200 microns. Three interchangeable lens sets give pixel sizes of 17, 27, and 45 in. Signals are processed through nitrogen-temperature JFET source-follower amplifiers, warm preamplifiers, and digital signal processors, and the system is controlled through a graphical user interface on a Macintosh computer. The camera has been used to image a wide variety of galactic and extragalactic far infrared sources.

Harper, D. AL, Jr.↗

NASA NTRS1996

Neutron Transmutation Doped (NTD) germanium thermistors for sub-mm bolometer applications

Recent advances in the development of neutron transmutation doped (NTD) semiconductor thermistors fabricated from natural and controlled isotopic composition germanium are reported. The near ideal doping uniformity that can be achieved with the NTD process, the device simplicity of NTD Ge thermistors and the high performance of cooled junction field effect transistor preamplifiers led to the widespread acceptance of these thermal sensors in ground-based, airborne and spaceborne radio telescopes. These features made possible the development of efficient bolometer arrays.

Haller, E. E.↗

NASA NTRS1961

Project Echo: 961-Mc Lower - Sideband Up - Converter for Satellite-Tracking Radar

A 961-Mc lower-sideband up-converter was specially designed to serve as preamplifier for the satellite-tracking radar used in Project Echo. The amplifier and its power supply are separately boxed and are installed directly behind the tracking antenna. The amplifier has been functioning most satisfactorily and has been used in routine manner to track the Echo satellite from horizon to horizon. This paper describes the design considerations, and details the special steps taken to ensure that the amplifier met the particular system needs of low noise, absolute stability, insensitivity to temperature fluctuations, and high input-power level before the onset of gain compression. The satisfactory operation of this amplifier confirms the great potentiality of parametric amplifiers as stable, low-noise, high-frequency receivers.

Uenohara, M.↗

NASA NTRS1961

A Technique for Increasing the Sensitivity of a Solid-State Fission Probe

A small silicon p-n junction wafer, when coated with uranium 235, can be used as a compact fission probe for low power flux and power mapping. Because of the inverse relation between the magnitude of a neutron-induced fission pulse and the inherent capacitance of the detecting element (capacitance is proportional to area), the size, and hence the sensitivity, of the semiconductor detector has been limited. New developments in the field of semiconductor detectors have made it possible to fabricate large area detectors which are essentially free from the capacitance effect. However, preliminary results indicate that they are much more susceptible to radiation damage than the detectors described in this report and as such may not be suitable for flux mapping. increasing the sensitivity cannot be accomplished by simply fabricating a larger detector. It has been observed that by combining the silicon p-n junction wafers in a series configuration the capacitance effect can be bypassed, and a fission probe can be made with a resultant increase in sensitivity by a factor of ten while sustaining only a minor decrease in pulse height. Analysis further indicates that for n silicon wafers in series, if n(C(sub i)) + C(sub c)/C(sub b) less than 0.1 where C(sub i) and C(sub c) are the preamplifier input and cable capacitances, respectively, and C(sub b) is the junction capacitance of a single silicon wafer, there should be no substantial reduction in pulse height due to series circuitry.

Steinberg, Robert↗

NASA NTRS1999

Preliminary Performance of CdZnTe Imaging Detector Prototypes

The promise of good energy and spatial resolution coupled with high efficiency and near-room-temperature operation has fuelled a large International effort to develop Cadmium-Zinc-Telluride (CdZnTe) for the hard-x-ray region. We present here preliminary results from our development of small-pixel imaging arrays fabricated on 5x5x1-mm and 5x5x2-mm spectroscopy and discriminator-grade material. Each array has 16 (4x4) 0.65-mm gold readout pads on a 0.75-mm pitch, with each pad connected to a discrete preamplifier via a pulse-welded gold wire. Each array is mounted on a 3-stage Peltier cooler and housed in an ion-pump-evacuated housing which also contains a hybrid micro-assembly for the 16 channels of electronics. We have investigated the energy resolution and approximate photopeak efficiency for each pixel at several energies and have used an ultra-fine beam x-ray generator to probe the performance at the pixel boundaries. Both arrays gave similar results, and at an optimum temperature of -20 C we achieved between 2 and 3% FWHM energy resolution at 60 keV and around 15% at 5.9 keV. We found that all the charge was contained within 1 pixel until very close to the pixels edge, where it would start to be shared with its neighbor. Even between pixels, all the charge would be appropriately shared with no apparently loss of efficiency or resolution. Full details of these measurements will be presented, together with their implications for future imaging-spectroscopy applications.

Ramsey, B.↗

NASA NTRS2000

A Real Time Differential GPS Tracking System for NASA Sounding Rockets

Sounding rockets are suborbital launch vehicles capable of carrying scientific payloads to several hundred miles in altitude. These missions return a variety of scientific data including: chemical makeup and physical processes taking place in the atmosphere, natural radiation surrounding the Earth, data on the Sun, stars, galaxies and many other phenomena. In addition, sounding rockets provide a reasonably economical means of conducting engineering tests for instruments and devices to be used on satellites and other spacecraft prior to their use in these more expensive missions. Typically around thirty of these rockets are launched each year, from established ranges at Wallops Island, Virginia; Poker Flat Research Range, Alaska; White Sands Missile Range, New Mexico and from a number of ranges outside the United States. Many times launches are conducted from temporary launch ranges in remote parts of the world requiring considerable expense to transport and operate tracking radars. In order to support these missions, an inverse differential GPS system has been developed. The flight system consists of a small, inexpensive receiver, a preamplifier and a wrap-around antenna. A rugged, compact, portable ground station extracts GPS data from the raw payload telemetry stream, performs a real time differential solution and graphically displays the rocket's path relative to a predicted trajectory plot. In addition to generating a real time navigation solution, the system has been used for payload recovery, timing, data timetagging, precise tracking of multiple payloads and slaving of optical tracking systems for over the horizon acquisition. This paper discusses, in detail, the flight and ground hardware, as well as data processing and operational aspects of the system, and provides evidence of the system accuracy.

Bull, Barton↗

NASA NTRS2001

Method and Apparatus for Determining Position Using Global Positioning Satellites

A global positioning satellite receiver having an antenna for receiving a L1 signal from a satellite is presented. The L1 signal is processed by a preamplifier stage including a band pass filter and a low noise amplifier and output as a radio frequency (RF) signal. A mixer receives and de-spreads the RF signal in response to a pseudo-random noise code, i,e., Gold code, generated by an internal pseudo-random noise code generator. A microprocessor enters a code tracking loop, such that during the code tracking loop, it addresses the pseudorandom code generator to cause the pseudo-random code generator to sequentially output pseudo-random codes corresponding to satellite codes used to spread the L1 signal, until correlation occurs. When an output of the mixer is indicative of the occurrence of correlation between the RF signal and the generated pseudo-random codes, the microprocessor caters an operational state which slows the receiver code sequence to stay locked with the satellite cede sequence. The output of the mixer is provided to a detector which, in turn, controls certain routines of the microprocessor. The microprocessor will output pseudo range information according to an interrupt routine in response detection of correlation. The pseudo range information is to be telemetered to a ground station which determines the position of the global positioning satellite receiver.

John L Ward↗

NASA NTRS1995

Sensor Systems for Space Life Sciences

Sensors 2000! (S2K!) is a NASA Ames Research Center engineering initiative designed to provide biosensor and bio-instrumentation systems technology expertise to NASA's life sciences spaceflight programs. S2K! covers the full spectrum of sensor technology applications, ranging from spaceflight hardware design and fabrication to advanced technology development, transfer and commercialization. S2K! is currently developing sensor systems for space biomedical applications on BION (a Russian biosatellite focused on Rhesus Monkey physiology) and NEUROLAB (a Space Shuttle flight devoted to neuroscience). It's Advanced Technology Development-Biosensors (ATD-B) project focuses efforts in five principle areas: biotelemetry Systems, chemical and biological sensors, physiological sensors, advanced instrumentation architectures, and data and information management. Technologies already developed and tested included, application-specific sensors, preamplifier hybrids, modular programmable signal conditioners, power conditioning and distribution systems, and a fully implantable dual channel biotelemeter. Systems currently under development include a portable receiver system compatible with an off-the-shelf analog biotelemeter, a 4 channel digital biotelemetry system which monitors pH, a multichannel, g-processor based PCM biotelemetry system, and hand-held personal monitoring systems. S2K! technology easily lends itself to telescience and telemedicine applications as a front-end measurement and data acquisition device, suitable for obtaining and configuring physiological information, and processing that information under control from a remote location.

Somps, Chris J.↗

NASA NTRS2002

An Extremely Wide Bandwidth, Low-Noise SIS Heterodyne Receiver Design for Millimeter and Submillimeter Observations

Millimeter and submillimeter heterodyne receivers using state-of-the-art SIS detectors are capable of extremely large instantaneous bandwidths with noise temperatures within a few Kelvin of the quantum limit. We present the design for a broadband, sensitive, heterodyne spectrometer under development for the Caltech Submillimeter Observatory (CSO). The 180-300 GHz double-sideband design uses a single SIS device excited by a full bandwidth, fixed-tuned waveguide probe on a silicon substrate. The IF output frequency (limited by the MMIC low noise IF preamplifier) is 6-18 GHz, providing an instantaneous RF bandwidth of 24 GHz (double-sideband). The SIS mixer conversion loss should be no more than 1-2 dB with mixer noise temperatures across the band within 10 K of the quantum limit. The single-sideband receiver noise temperature goal is 70 K. The wide instantaneous bandwidth and low noise will result in an instrument capable of a variety of important astrophysical observations beyond the capabilities of current instruments. Lab testing of the receiver will begin in the summer of 2002, and the first use on the CSO should occur in the spring of 2003.

Sumner, Matthew↗

NASA NTRS2003

Sounding of the Ion Energization Region: Resolving Ambiguities

Dartmouth College provided a single-channel high-frequency wave receiver to the Sounding of the Ion Energization Region: Resolving Ambiguities (SIERRA) rocket experiment launched from Poker Flat, Alaska, in January 2002. The receiver used signals from booms, probes, preamplifiers, and differential amplifiers provided by Cornell University coinvestigators. Output was to a dedicated 5 MHz telemetry link provided by WFF, with a small amount of additional Pulse Code Modulation (PCM) telemetry required for the receiver gain information. We also performed preliminary analysis of the data. The work completed is outlined below, in chronological order.

LaBelle, James↗