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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Organics in water contamination analyzer, phase 1

The requirements which would result in identifying the components of an automatic analytical system for the analysis of specific organic compounds in the space station potable water supply are defined. The gas chromatographic system for such an analysis is limited to commercially available off-the-shelf hardware and includes the sample inlet, an ionization detector, capillary columns as well as computerized compound identification. The sampling system will be a special variation of the purge and trap Tenax mode using six-port valves and a 500 microliter water sample. Capillary columns used for the separating of contaminants will be bonded phase fused silica with a silicone stationary phase. Two detectors can be used: photoionization and far ultraviolet, since they are sensitive and compatible with capillary columns. A computer system evaluation and program with the principle of compound identification based on the retention index is presented.

Source record↗
NASA NTRS1977

Interferometer mirror tilt correcting system

An interferometer is described, having several means for automatically adjusting the angular tilt of a reflecting surface in one of two paths to maintain the exit beams from the two paths parallel to each other. Three detectors at the output of the interferometer were disposed on mutually perpendicular axes which define a plane normal to the nominal exit beam axis. One detector at the origin of the axes was used as a reference for separate phase difference comparison with the outputs of the other two detectors on the X and Y axes to develop servo error signals.

Schindler, R. A.↗
NASA NTRS2014

Micro-Spec: an Integrated, Direct-Detection Spectrometer for Far-Infrared and Submillimeter Astronomy

The far-infrared and submillimeter portions of the electromagnetic spectrum provide a unique view of the astrophysical processes present in the early universe. Our ability to fully explore this rich spectral region has been limited, however, by the size and cost of the cryogenic spectrometers required to carry out such measurements. Micro-Spec (u-Spec) is a high-sensitivity, direct-detection spectrometer concept working in the 450-1000 micromillimeter wavelength range which will enable a wide range of flight missions that would otherwise be challenging due to the large size of current instruments with the required spectral resolution and sensitivity. The spectrometer design utilizes two internal antenna arrays, one for transmitting and one for receiving, superconducting microstrip transmission lines for power division and phase delay, and an array of microwave kinetic inductance detectors (MKIDs) to achieve these goals. The instrument will be integrated on a approximately 10 square cm silicon chip and can therefore become an important capability under the low background conditions accessible via space and high-altitude borne platforms. In this paper, an optical design methodology for Micro-Spec is presented, with particular attention given to its twodimensional diffractive region, where the light of different wavelengths is focused on the different detectors. The method is based on the maximization of the instrument resolving power and minimization of the RMS phase error on the instrument focal plane. This two-step optimization can generate geometrical configurations given specific requirements on spectrometer size, operating spectral range and performance. A point design with resolving power of 257, an RMS phase error less than 0.1 radians and four stigmatic points was developed for initial demonstration and will be the basis of future instruments with resolving power up to about 1200.

microwave kinetic inductance detectors (MKIDs)↗
NASA NTRS2018

WFIRST Coronagraph Detector Trap Modeling Results and Improvements

The WFIRST coronagraph is being designed to detect and characterize mature exoplanets through the starlight reflected from their surfaces and atmospheres. The light incident on the detector from these distant exoplanets is estimated to be on the order of a few photons per pixel per hour. To measure such small signals, the project has baselined the CCD201 detector made by e2v, a low-noise and high-efficiency electron-multiplying charge-coupled device (EMCCD), and has instituted a rigorous test and modeling program to characterize the device prior to flight. An important consideration is detector performance degradation over the proposed mission lifetime due to radiation exposure in space. To quantify this estimated loss in performance, the project has built a detector trap model that takes into account detailed trap interactions at the sub-pixel level, including stochastic trap capture and release, and the deferment of charge into subsequent pixels during parallel and serial clocking of the pseudo-two-phase CCD201 device. This paper describes recent detector trap model improvements and modeling results.

Holland, Andrew↗
NASA NTRS1974

Simplified OMEGA receivers

The details are presented of methods for providing OMEGA navigational information including the receiver problem at the antenna and informational display and housekeeping systems based on some 4 bit data processing concepts. Topics discussed include the problem of limiters, zero crossing detectors, signal envelopes, internal timing circuits, phase counters, lane position displays, signal integrators, and software mapping problems.

Burhans, R. W.↗
NASA NTRS1979

Construction and testing of the 2.5m mass driver

Presented are the designs used in the construction of the 2.5 m mass driver and the results of the initial testing program. The mass driver consists of equal length sections of acceleration and deceleration each containing 59 drive coils of 13.1 cm caliber. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. The drive coils are individually energized through SCR's with timing supplied by position sensing optical detectors. The drive consists of two phases which operate in quadrature. The initial bucket to be propelled through the mass driver contains two coils of aluminum wire chilled to liquid nitrogen temperatures to momentarily sustain superconducting field intensities. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the mass driver. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/s.

Snow, W. R.↗
NASA NTRS1979

Observations of Cygnus X-3 above 50 keV

Cygnus X-3 was observed in the energy range 50-400 keV using a balloon-borne, actively collimated, NaI(Tl) scintillation detector. The observation was made from phase 0.45-0.91 of the 4.8 hour period. The photon number spectrum was well represented by a power law with index -2.2. The flux increased throughout the observation, consistent with a highly asymmetric light curve with a peak near phase 0.9.

Meegan, C. A.↗
NASA NTRS1985

A method to improve observations of gamma-ray sources near 10 (15) eV

Now that sources of gamma rays near 10 to the 15th power eV have been identified, there is a need for telescopes which can study in detail the high energy gamma ray emissions from these sources. The capabilities of a Cerenkov detector which can track a source at large zenith angle (small elevation angle) are analyzed. Because the observed showers must then develop far from the detector, the effective detection area is very large. During a single half-hour hot phase of Cygnus X-3, for example, it may be possible to detect 45 signal showers compared with 10 background showers. Time structure within the hot phase may then be discernible. The precise capabilities of the detector depend on its mirror size, angular acceptance, electronic speed, coincidence properties, etc. Calculations are presented for one feasible design using mirrors of an improved Fly's Eye type.

Sommers, P.↗
NASA NTRS1995

A Single Chip VLSI Implementation of a QPSK/SQPSK Demodulator for a VSAT Receiver Station

This thesis presents a VLSI implementation of a QPSK/SQPSK demodulator. It is designed to be employed in a VSAT earth station that utilizes the FDMA/TDM link. A single chip architecture is used to enable this chip to be easily employed in the VSAT system. This demodulator contains lowpass filters, integrate and dump units, unique word detectors, a timing recovery unit, a phase recovery unit and a down conversion unit. The design stages start with a functional representation of the system by using the C programming language. Then it progresses into a register based representation using the VHDL language. The layout components are designed based on these VHDL models and simulated. Component generators are developed for the adder, multiplier, read-only memory and serial access memory in order to shorten the design time. These sub-components are then block routed to form the main components of the system. The main components are block routed to form the final demodulator.

Kwatra, S. C.↗
NASA NTRS1996

Optimal Signal Filtration in Optical Sensors with Natural Squeezing of Vacuum Noises

The structure of optimal receiver is discussed for optical sensor measuring a small displacement of probe mass. Due to nonlinear interaction of the field and the mirror, a reflected wave is in squeezed state (natural squeezing), two quadratures of which are correlated and therefore one can increase signal-to-noise ratio and overcome the SQL. A measurement procedure realizing such correlation processing of two quadratures is clarified. The required combination of quadratures can be produced via mixing of pump field reflected from the mirror with local oscillator phase modulated field in duel-detector homodyne scheme. Such measurement procedure could be useful not only for resonant bar gravitational detector but for laser longbase interferometric detectors as well.

Gusev, A. V.↗
NASA NTRS1997

The GLAST Mission: Using Scintillating Fibers as Both the Tracker and the Calorimeter

The Gamma-Ray Large Area Space Telescope (GLAST) has been identified as the next major NASA mission in gamma-ray astronomy. It will operate at energies above 20 MeV to study some of the most energetic objects in the Universe. While the baseline tracker detector for GLAST during the study phase is based on silicon strips, we believe that scintillating fibers have considerable advantages for this purpose. Among the performance advantages are: larger effective area, better angular resolution at low energies and larger field of view. Practical advantages include: lower cost, the use of a common technology for both the tracker and the calorimeter, lower power consumption, and a simplified thermal design. Several alternative readout schemes for the fibers are under study.

Fisman, Gerald J.↗
NASA NTRS2014

Micro-spec: an Integrated Direct-detection Spectrometer for Far-infrared Space Telescopes

The far-infrared and submillimeter portions of the electromagnetic spectrum provide a unique view of the astrophysical processes present in the early universe. Our ability to fully explore this rich spectral region has been limited, however, by the size and cost of the cryogenic spectrometers required to carry out such measurements.Micro-Spec (μ-Spec) is a high-sensitivity, direct-detection spectrometer concept working in the 450-1000 (micrometers) wavelength range which will enable a wide range of flight missions that would otherwise be challenging due tothe large size of current instruments with the required spectral resolution and sensitivity. The spectrometer design utilizes two internal antenna arrays, one for transmitting and one for receiving, superconducting microstrip transmission lines for power division and phase delay, and an array of microwave kinetic inductance detectors (MKIDs) to achieve these goals. The instrument will be integrated on a approximately 10 sq cm silicon chip and can therefore become an important capability under the low background conditions accessible via space and high-altitude borne platforms. In this paper, an optical design methodology for micro-Spec is presented, with particular attention given to its two-dimensional diffractive region, where the light of different wavelengths is focused on the different detectors. The method is based on the maximization of the instrument resolving power and minimization of the RMS phase error on the instrument focal plane. This two-step optimization can generate geometrical configurations given specific requirements on spectrometer size, operating spectral range and performance.Two point designs with resolving power of 260 and 520 and an RMS phase error less than approximately 0.004 radians were developed for initial demonstration and will be the basis of future instruments with resolving power up to about 1200.

Far-infrared↗
NASA NTRS2016

The Neutron Star Interior Composition Explorer (NICER): Design and Development

During 2014 and 2015, NASA's Neutron star Interior Composition Explorer (NICER) mission proceeded successfully through Phase C, Design and Development. An X-ray (0.2{12 keV) astrophysics payload destined for the International Space Station, NICER is manifested for launch in early 2017 on the Commercial Resupply Services SpaceX-11 flight. Its scientific objectives are to investigate the internal structure, dynamics, and energetics of neutron stars, the densest objects in the universe. During Phase C, flight components including optics, detectors, the optical bench, pointing actuators, electronics, and others were subjected to environmental testing and integrated to form the flight payload. A custom-built facility was used to co-align and integrate the X-ray \concentrator" optics and silicon-drift detectors. Ground calibration provided robust performance measures of the optical (at NASA's Goddard Space Flight Center) and detector (at the Massachusetts Institute of Technology) subsystems, while comprehensive functional tests prior to payload-level environmental testing met all instrument performance requirements. We describe here the implementation of NICER's major subsystems, summarize their performance and calibration, and outline the component-level testing that was successfully applied.

SEXTANT↗
NASA NTRS2007

Digital Signal Processing Techniques for the GIFTS SM EDU

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) Sensor Module (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiance using a Fourier transform spectrometer (FTS). The GIFTS instrument employs three Focal Plane Arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes several digital signal processing (DSP) techniques involved in the development of the calibration model. In the first stage, the measured raw interferograms must undergo a series of processing steps that include filtering, decimation, and detector nonlinearity correction. The digital filtering is achieved by employing a linear-phase even-length FIR complex filter that is designed based on the optimum equiripple criteria. Next, the detector nonlinearity effect is compensated for using a set of pre-determined detector response characteristics. In the next stage, a phase correction algorithm is applied to the decimated interferograms. This is accomplished by first estimating the phase function from the spectral phase response of the windowed interferogram, and then correcting the entire interferogram based on the estimated phase function. In the calibration stage, we first compute the spectral responsivity based on the previous results and the ideal Planck blackbody spectra at the given temperatures, from which, the calibrated ambient blackbody (ABB), hot blackbody (HBB), and scene spectra can be obtained. In the post-calibration stage, we estimate the Noise Equivalent Spectral Radiance (NESR) from the calibrated ABB and HBB spectra. The NESR is generally considered as a measure of the instrument noise performance, and can be estimated as the standard deviation of calibrated radiance spectra from multiple scans. To obtain an estimate of the FPA performance, we developed an efficient method of generating pixel performance assessments. In addition, a random pixel selection scheme is developed based on the pixel performance evaluation. This would allow us to perform the calibration procedures on a random pixel population that is a good statistical representation of the entire FPA. The design and implementation of each individual component will be discussed in details.

Tian, Jialin↗
NASA NTRS1993

Performance of the FOS Detectors in a Variable External Magnetic Field

We present the results of an investigation of the in-orbit performance of the Digicon detectors in the Faint Object Spectrograph (FOS), conducted as part of the commissioning phase of the Hubble Space Telescope. This paper includes orbital results on detector background noise, sensor image stability, and photometric stability along with several typical FOS observations. New techniques for suppressing cosmic ray induced background and geomagnetic induced image motion in electron tube detectors are also discussed.

Fitch, J. E.↗
NASA NTRS1977

On propagation direction of ring current proton ULF waves observed by ATS 6 at 6.6 R sub E

From June 11 to September 16, 1974, the NOAA low-energy proton detector on board the ATS 6 satellite observed 71 cases of ultralow-frequency oscillations of proton flux intensities. The oscillation periods varied from 40 s to 6 min, and the events were observed most frequently during moderate geomagnetic conditions. The flux oscillations occurred at various local times, yet almost two thirds of the events were detected in the near-dusk region of the magnetosphere. For a majority of the events in this set a substantial phase shift in flux oscillation was detected between different energy channels and/or between two oppositely oriented detector telescopes. The phase shift is mainly due to the finite gyroradius effect of the protons gyrating in the geomagnetic field. By examining this finite gyroradius effect on the perturbed particle distribution function associated with the wave in a nonuniform magnetic field, the propagation direction of the wave from particle observations made by a single spacecraft is determined

Su, S.-Y.↗
NASA NTRS1977

Length controlled stabilized mode-lock ND:YAG laser

A method and apparatus for stabilizing the amplitude and repetition rate of mode-locked Nd:YAG laser pulses by controlling the laser length through a feedback loop are described. The end mirror of the laser is mounted on a piezoelectric crystal which is dithered at a low frequency. A portion of fundamental 1.06 micrometer laser radiation is converted into its second harmonic frequency, and the average power of the second harmonic frequency is detected by an integrating detector. The amount of the power of the second harmonic frequency depends on the match between the optical length of the laser cavity and the mode-lock frequency. The length is controlled by a feedback loop which phase compares the output of the second harmonic detector to the piezoelectric crystal dither signal.

Sigfred, J.↗