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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Advanced Radiation Detectors and Detector Systems Research

Real‐time awareness of space radiation is critical for missions beyond LEO. Missions to the Moon, Mars, Near‐Earth‐Objects (NEOs), inner and outer planets, as well as other destinations in space, will require embedded instrumentation to provide feedback for “smart”, adaptive control systems. Precision instrumentation will also be needed to provide improved data for space radiation modeling and space weather forecasting and awareness. Compact instrumentation on small platforms such as CubeSats and other small space‐faring vehicles will provide a better understanding of the space radiation environment by supplying data from multiple locations in space where information is yet unknown. Compact integrable solid‐state detectors with low noise and high tolerance of operation in a radiation environment are enabled by the application of Wide Band Gap semiconductors as radiation detectors. NASA Glenn Research Center (GRC) is applying its expertise and facilities in harsh environment instrumentation to develop supporting technologies that enable improved instruments for space science missions. A variety of radiation detectors are under development, such as silicon carbide semiconductor detectors, for applications to space science, lunar prospecting, and fission power systems.

Field and particle detectors↗
NASA NTRS1976

Analysis of Skylab follow-on orbital neutron environmental data

The data base and techniques developed for Skylab experiment ED76 were used to process and analyze data from 54 solid dielectric track recorders. The processing of mica and cellulose nitrate for neutron and proton detectors is described. The measured time integrated fission rates for seven detectors is given.

Source record↗
NASA NTRS1984

Spectral feature of 31 December 1981 gamma-ray burst not confirmed

Measurements of a gamma ray burst at 01:37 UT on December 31, 1981 using the SMM gamma ray spectrometer (GRS) are compared with those made by the Konus instruments on Veneras 11-14. Burst time profiles, photon spectra, and detector energy loss spectra for three time intervals are compared for the GRS and the Konus instruments. It is concluded that the SMM spectra exhibit no evidence for the presence of emission features reported by the Konus group.

Nolan, P. L.↗
NASA NTRS2013

Narrow Line X-Ray Calibration Source for High Resolution Microcalorimeters

We are developing a narrow line calibration source for use with X-ray microcalorimeters. At energies below 300 electronvolts fluorescent lines are intrinsically broad, making calibration of high resolution detectors difficult. This source consists of a 405 nanometers (3 electronvolts) laser diode coupled to an optical fiber. The diode is pulsed to create approximately one hundred photons in a few microseconds. If the pulses are short compared to the rise time of the detector, they will be detected as single events with a total energy in the soft X-ray range. Poisson fluctuations in photon number per pulse create a comb of X-ray lines with 3 electronvolts spacing, so detectors with energy resolution better than 2 electronvolts are required to resolve the individual lines. Our currently unstabilized diode has a multimode width less than 1 nanometer, giving a 300 electronvolt event a Full width at half maximum (FWHM) less than 0.1 electronvolts. By varying the driving voltage, or pulse width, the source can produce a comb centered on a wide range of energies. The calibration events are produced at precisely known times. This allows continuous calibration of a flight mission without contaminating the observed spectrum and with minimal deadtime.

high resolution detectors↗
NASA NTRS2000

Micromachined Thermoelectric Sensors and Arrays and Process for Producing

Linear arrays with up to 63 micromachined thermopile infrared detectors on silicon substrates have been constructed and tested. Each detector consists of a suspended silicon nitride membrane with 11 thermocouples of sputtered Bi-Te and Bi-Sb-Te thermoelectric elements films. At room temperature and under vacuum these detectors exhibit response times of 99 ms, zero frequency D* values of 1.4 x 10(exp 9) cmHz(exp 1/2)/W and responsivity values of 1100 V/W when viewing a 1000 K blackbody source. The only measured source of noise above 20 mHz is Johnson noise from the detector resistance. These results represent the best performance reported to date for an array of thermopile detectors. The arrays are well suited for uncooled dispersive point spectrometers. In another embodiment, also with Bi-Te and Bi-Sb-Te thermoelectric materials on micromachined silicon nitride membranes, detector arrays have been produced with D* values as high as 2.2 x 10(exp 9) cm Hz(exp 1/2)/W for 83 ms response times.

Foote, Marc C.↗
NASA NTRS1981

Observations of gamma radiation between 0.4 MeV and 7 MeV at balloon altitudes using a Compton telescope

Balloon-borne measurements of the atmospheric and diffuse gamma-ray flux in the energy range 0.4-7.0 MeV with a Compton telescope, which included pulse-shape discrimination of the first scattering detector and a time-of-flight system between the first and second detector elements, are reported. Comparison of the diffuse cosmic gamma-ray flux to the atmospheric gamma rays indicates that 0.2-5.0 MeV is the optimum energy range for measurements made at the top of the earth's atmosphere. The measured total atmospheric gamma-ray flux between zero and 40 deg has an energy spectrum that agrees with the calculations of Ling (1975). Observations indicate that the ratio of the diffuse to atmospheric gamma ray fluxes at 3.5 g/sq cm is a maximum, about 1.0, between 0.7 and 3.0 MeV.

Lockwood, J. A.↗
NASA NTRS1988

ORFEUS focal plane instrumentation: The Berkeley spectrometer

A spectrograph for the ORFEUS mission that incorporates four varied line-space, spherically figured diffraction gratings was designed. The ORFEUS, a 1-m normal incidence telescope is equipped with 2 focal plane spectrographs. The Berkeley spectrograph was developed with an optimizing raytracing computer code. Each grating accepts the light from 20 percent of the aperture of the telescope primary mirror and has a unique set of characteristics to cover a sub-bandpass within the 390 to 1200 A spectral range. Two photon-counting detectors incorporating a time delay readout system are used to record the spectra from all four gratings simultaneously. The nominal design achieves a spectral resolution (FWHM) in excess of 5500 at all wavelengths within the bandpass. The resolution is limited primarily by the detector spatial resolution. The 1 sigma astigmatism of this design varies between 13 and 150 micrometer on the same focal surface. An independent, direct imaging system tracks the drift of the target within the spectrometer aperture and allows measurement of the misalignment between the telescope optical axis and that of the external star tracker. The resolution and astigmatism achievable with this design are superior to those of a standard Rowland spectrograph designed with the same constraints.

Hurwitz, Mark↗
NASA NTRS1985

The effect of the interplanetary magnetic field on sidereal variations observed at medium depth underground detectors

It has been known for some years that the intensity variations in sidereal time observed by muon detectors at moderate underground depths are sensitive to the polarity of the interplanetary magnetic field (ipmf) near the Earth. There are differences in the response to these anisotropies as observed in the Norhtern and southern hemispheres. When fully understood, the nature of the anisotropy seems likely to provide information on the 3-dimensional structure of the heliomagnetosphere, its time variations, and its linking with the local interstellar field. The summation harmonic dials for the sidereal diurnal variation during 1958 to 1982 show that there is a strong dependence on whether the ipmf near the Earth is directed outwards from the Sun or inwards it.

Humble, J. E.↗
NASA NTRS2011

The Landsat Data Continuity Mission Operational Land Imager: Radiometric Performance

The Operational Land Imager (OLI) is one of two instruments to fly on the Landsat Data Continuity Mission (LDCM), which is scheduled to launch in December 2012 to become the 8th in the series of Landsat satellites. The OLI images in the solar reflective part of the spectrum, with bands similar to bands 1-5, 7 and the panchromatic band on the Landsat-7 ETM+ instrument. In addition, it has a 20 nm bandpass spectral band at 443 nm for coastal and aerosol studies and a 30 nm band at 1375 nm to aid in cirrus cloud detection. Like ETM+, spatial resolution is 30 m in the all but the panchromatic band, which is 15 meters. OLI is a pushbroom radiometer with approximately 6000 detectors per 30 meter band as opposed to the 16 detectors per band on the whiskbroom ETM+. Data are quantized to 12 bits on OLI as opposed to 8 bits on ETM+ to take advantage of the improved signal to noise ratio provided by the pushbroom design. The saturation radiances are higher on OLI than ETM+ to effectively eliminate saturation issues over bright Earth targets. OLI includes dual solar diffusers for on-orbit absolute and relative (detector to detector) radiometric calibration. Additionally, OLI has 3 sets of on-board lamps that illuminate the OLI focal plane through the full optical system, providing additional checks on the OLI's response[l]. OLI has been designed and built by Ball Aerospace & Technology Corp. (BATC) and is currently undergoing testing and calibration in preparation for delivery in Spring 2011. Final pre-launch performance results should be available in time for presentation at the conference. Preliminary results will be presented below. These results are based on the performance of the Engineering Development Unit (EDU) that was radiometrically tested at the integrated instrument level in 2010 and assembly level measurements made on the flight unit. Signal-to-Noise (SNR) performance: One of the advantages of a pushbroom system is the increased dwell time of the detectors allowing for significantly higher SNR than equivalent aperture whiskbroom systems. OLI performance based on the EDU at the "typical" radiance level as specified in the OLI requirements document are about 10 times better than ETM+ performance and 2-3 times better than the requirements for OLI (Table 1).

Markham, Brian↗
NASA NTRS2020

Comparing complex impedance and bias step measurements of Simons Observatory transition edge sensors

The Simons Observatory (SO) will perform ground-based observations of the cosmic microwave background (CMB) with several small and large aperture telescopes, each outfitted with thousands to tens of thousands of superconducting aluminum manganese (AlMn) transition-edge sensor bolometers (TESs). In-situ characterization of TES responsivities and effective time constants will be required multiple times each observing-day for calibrating time-streams during CMB map-making. Effective time constants are typically estimated in the field by briefly applying small amplitude square-waves on top of the TES DC biases, and fitting exponential decays in the bolometer response. These so-called “bias step” measurements can be rapidly implemented across entire arrays and therefore are attractive because they take up little observing time. However, individual detector complex impedance measurements, while too slow to implement during observations, can provide a fuller picture of the TES model and a better understanding of its temporal response. Here, we present the results of dark TES characterization of many prototype SO bolometers and compare the effective thermal time constants measured via bias steps to those derived from complex impedance data.

Nicholas F. Cothard↗
NASA NTRS2014

Effects of Low Earth Orbit on Docking Seal Materials

Spacecraft docking seals are typically made of silicone elastomers. When such seals are exposed to low Earth orbit (LEO) conditions, they can suffer damage from ultraviolet (UV) radiation and atomic oxygen (AO, or monoatomic oxygen, the predominant oxygen species in LEO). An experiment flew on the International Space Station (ISS) to measure the effects of LEO on seal materials S0383-70 and ELA-SA-401 and various mating counterface materials which included anodized aluminum. Samples flown in different orientations received different amounts of UV and AO. The hypotheses were that most of the damage would be from UV, and 10 days or more of exposure in LEO would badly damage the seals. Eighteen seals were exposed for 543 days in ram (windward), zenith (away from Earth), or wake (leeward) orientations, and 15 control samples (not flown) provided undamaged baseline leakage. To determine post-flight leak rates, each of the 33 seals were placed in an O-ring groove of a leak test fixture and pressure tested over time. Resistance temperature detectors (RTDs), pressure transducers, and LabVIEW (National Instruments) programs were used to measure and analyze the temperature and pressure and calculate leakage. Average leakage of control samples was 2.6 x 10(exp -7) lbs/day. LEO exposure did not considerably damage ELA-SA-401. The S0383-70 flight samples leaked at least 10 times more than ELA-SA-401 in all cases except one, demonstrating that ELA-SA-401 may be a more suitable sealing material in LEO. AO caused greater damage than UV; samples in ram orientation (receiving an AO fluence of 4.3 x 10(exp 21) atoms/(sq cm) and in wake (2.9x 10(exp 20) atoms/(sq cm)) leaked more than those in zenith orientation (1.58 x 10(exp 20) atoms/(sq cm)), whereas variations in UV exposure did not seem to affect the samples. Exposure to LEO did less damage to the seals than hypothesized, and the data did not support the conjecture that UV causes more damage than AO.

Leakage↗
NASA NTRS1990

Three-dimensional acousto-optic spectrum analysis

A three-dimensional acoustooptic spectrum analyzer with subhertz resolution is demonstrated experimentally. The first and second dimensions are the two spatial dimensions of the output detector array, and the third dimension is time as sampled by the detector array frame rate. A superfine resolution of 0.12 Hz has been achieved.

Ansari, Homayoon↗
NASA NTRS1975

Uniform sampling analysis of a hybrid phase-locked loop with a sample-and-hold phase detector

Phase-locked-loop (PLL) bit synchronizers often employ integrate-and-dump type phase detectors that provide phase error information only at discrete points in time. Usually these phase detectors are followed by sample-and-hold circuits to produce a stairstep error voltage as the input to a standard analog circuit loop filter. When the loop is configured in this manner, it is referred to as a hybrid PLL. Sampled-data analysis methods (Z transforms) are used to determine the stability and transient response of this loop.

Barab, S.↗
NASA NTRS2001

In-Situ Detections of a Satellite Breakup by the SPADUS Experiment

For the first time, a particle detector in Earth orbit has provided evidence to directly link sub-millimeter orbital debris to a specific satellite breakup. The University of Chicago's Space Dust instrument (SPADUS), on the U.S. Air Force's Advanced Research and Global Observation Satellite (ARGOS), has been operating in a nearly polar orbit at an altitude of about 830 km since soon after its launch on 23 February 1999. The experiment was designed primarily to detect small natural and man-made particles less than 100 microns in diameter. Using a dual-plane Polyvinylidene Fluoride (PVDF)-based detection system, SPADUS can measure dust particle flux, mass distribution, velocity, and trajectory. During its first year in orbit, SPADUS recorded 195 impacts, about one impact every two days. In late March 2000 the instrument detection rate soared by approximately an order of magnitude, suggesting a potential encounter with a cloud or stream of debris. A review of the impact times and ARGOS orbital characteristics indicated that most of the detections occurred at multiples of half-revolution intervals deep in the northern and southern hemispheres, with a clear majority of impacts found in the latter. Orbital analyses linked these impact events to the orbital plane intersections of ARGOS and the debris cloud of a Chinese orbital stage (International Designator 1999-057C, US Satellite Number 25942) which had undergone a severe fragmentation on 11 March 2000 at an altitude 100 km below that of ARGOS. Approximately 40 of the SPADUS detections during the period 25 March 1 April could be associated with the postulated Chinese debris cloud. Other periods of high impact flux on SPADUS may be related to debris clouds from different sources.

Tuzzolino, A. J.↗
NASA NTRS1990

Low dark current photovoltaic multiquantum well long wavelength infrared detectors

The authors have, for the first time, demonstrated photovoltaic detection for an multiple quantum well (MQW) detector. With a blocking layer, the MQW detector exhibits Schottky I-V characteristics with extremely low dark current and excellent ideality factor. The dark current is 5 times 10(exp -14) A for an 100x100 square micron 10 micron detector at 40 K, 8 to 9 orders of magnitude lower than that of a similar 10 micron MQW detector without blocking layer. The ideality factor is about 1.01 to 1.05 at T = 40 to 80 K. The measured barrier height is consistent with the energy difference between first excited states and ground states, or the peak of spectral response. The authors also, for the first time, report the measured effective Richardson constant (A asterisk asterisk) for the GaAs/AlGaAs heterojunction using this blocking layer structure. The A asterisk asterisk is low approx. 2.3 A/sq cm/K(exp 2).

Wu, C. S.↗
NASA NTRS2003

Single Station System and Method of Locating Lightning Strikes

An embodiment of the present invention uses a single detection system to approximate a location of lightning strikes. This system is triggered by a broadband RF detector and measures a time until the arrival of a leading edge of the thunder acoustic pulse. This time difference is used to determine a slant range R from the detector to the closest approach of the lightning. The azimuth and elevation are determined by an array of acoustic sensors. The leading edge of the thunder waveform is cross-correlated between the various acoustic sensors in the array to determine the difference in time of arrival, AT. A set of AT S is used to determine the direction of arrival, AZ and EL. The three estimated variables (R, AZ, EL) are used to locate a probable point of the lightning strike.

Medelius, Pedro J.↗
NASA NTRS2016

Performance of NICER Flight X-Ray Concentrator

Neutron star Interior Composition ExploreR (NICER) is a NASA instrument to be onboard International Space Station, which is equipped with 56 pairs of an X-ray concentrator (XRC) and a silicon drift detector for high timing observations. The XRC is based on an epoxy replicated thin aluminum foil X-ray mirror, similar to those of Suzaku and ASTRO-H (Hitomi), but only a single stage parabolic grazing incidence optic. Each has a focal length of 1.085 m and a diameter of 105 mm, with 24 confocally aligned parabolic shells. Grazing incident angles to individual shells range from 0.4 to 1.4 deg. The flight 56 XRCs have been completed and successfully delivered to the payload integration. All the XRC was characterized at the NASA/GSFC 100-m X-ray beamline using 1.5 keV X-rays (some of them are also at 4.5 keV). The XRC performance, effective area and point spread function, was measured by a CCD camera and a proportional counter. The average effective area is about 44 sq cm at 1.5 keV and about 18 sq cm at 4.5 keV, which is consistent with a micro-roughness of 0.5 nm from individual shell reflectivity measurements. The XRC focuses about 91% of X-rays into a 2mm aperture at the focal plane, which is the NICER detector window size. Each XRC weighs only 325 g. These performance met the project requirement. In this paper, we will present summary of the flight XRC performance as well as co-alignment results of the 56 XRCs on the flight payload as it is important to estimate the total effective for astronomical observations.

X-ray concentrator↗