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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 721 records · Page 40
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NASA NTRS1995

Determination of Benzene, Toluene, and Xylene by means of an ion mobility spectrometer device using photoionization

The continuous monitoring of changes on the quality of ambient air is a field of advantage of ion mobility spectrometry. Benzene, Toluene, and Xylene are substances of special interest because of their toxicity. We present an optimized drift tube for ion mobility spectrometers, which uses photo-ionization tubes to produce the ions to be analyzed. The actual version of this drift tube has a length of 45 mm, an electric field strength established within the drift tube of about 180 V/cm and a shutter-opening-time of 400 mus. With the hydrogen tube used for ionisation a mean flux of 10(exp 12) photons/sq cm s was established for the experiments described. We discuss the results of investigations on Benzene, Toluene, and Xylene in normal used gasoline SUPER. The detection limits obtained with the ion mobility spectrometer developed in co-operation are in the range of 10 ppbv in this case. Normally, charge transfer from Benzene ions to Toluene takes place. Nevertheless the simultaneous determination in mixtures is possible by a data evaluation procedure developed for this case. The interferences found between Xylene and others are rather weak. The ion mobility spectra of different concentrations of gasoline SUPER are attached as an example for the resolution and the detection limit of the instrument developed. Resolution and sensitivity of the system are well demonstrated. A hand-held portable device produced just now is to be tested for special environmental analytical problems in some industrial and scientific laboratories in Germany.

Leonhardt, J. W.↗
NASA NTRS1995

Combined hyperspatial and hyperspectral imaging spectrometer concept

There is a user need for increasing spatial and spectral resolution in Earth Observation (EO) optical instrumentation. Higher spectral resolution will be achieved by the introduction of spaceborne imaging spectrometers. Higher spatial resolutions of 1 - 3m will be achieved also, but at the expense of sensor redesign, higher communications bandwidth, high data processing volumes, and therefore, at the risk of time delays due to large volume data-handling bottlenecks. This paper discusses a design concept whereby the hyperspectral properties of a spaceborne imaging spectrometer can be used to increase the image spatial resolution, without such adverse cost impact.

Burke, Ian↗
NASA NTRS1995

Airborne Visible/Infrared Imaging Spectrometer (AVIRIS): Sensor improvements for 1994 and 1995

AVIRIS is a NASA-sponsored Earth-remote-sensing imaging spectrometer designed, built and operated by the Jet Propulsion Laboratory (JPL). While AVIRIS has been operational since 1989, major improvements have been completed in most of the sensor subsystems during the winter maintenance cycles. As a consequence of these efforts, the capabilities of AVIRIS to reliably acquire and deliver consistently high quality, calibrated imaging spectrometer data continue to improve annually, significantly over those in 1989. Improvements to AVIRIS prior to 1994 have been described previously. This paper details recent and planned improvements to AVIRIS in the sensor task.

Sarture, C. M.↗
NASA NTRS1994

ASCA solid state imaging spectrometer observations of O stars

We report ASCA Solid State Imaging Spectrometer (SIS) X-ray observations of the O stars delta Ori and lambda Ori. The energy resolution of the SIS allows us to resolve features in the O star X-ray spectra which are not apparent in spectra obtained by X-ray spectrometers with lower energy resolution. SIS spectra from both stars show evidence of line emission, suggesting the thermal nature of the X-ray source. However, the observed line strengths are different for the two stars. The observed stellar X-ray spectra are not well described by isothermal models although absorbed thermal emission models with two or more temperatures can provide an adequate fit to the data. For both stars we present evidence of absorbing columns significantly larger than the known Interstellar Medium (ISM) columns, indicative of absorption by a circumstellar medium, presumably the stellar winds. In addition, the lambda Ori spectrum shows the presence of emission at energies greater than 3 keV which is not seen in the delta Ori spectrum.

Corcoran, M. F.↗
NASA NTRS1995

Performance of a focused cavity aerosol spectrometer for measurements in the stratosphere of particle size in the 0.06-2.0-micrometer-diameter range

A focused cavity aerosol spectrometer aboard a NASA ER-2 high-altitude aircraft provided high-resolution measurements of the size of the stratospheric particles in the 0.06-2.0-micrometer-diameter range in flights following the eruption of Mount Pinatubo in 1991. Effects of anisokinetic sampling and evaporation in the sampling system were accounted for by means adapted and specifically developed for this instrument. Calibrations with monodisperse aerosol particles provided the instrument's response matrix, which upon inversion during data reduction yielded the particle size distributions. The resultant dataset is internally consistent and generally shows agreement to within a factor of 2 with comparable measurements simultaneously obtained by a condensation nuclei counter, a forward-scattering spectrometer probe, and aerosol particle impactors, as well as with nearby extinction profiles obtained by satellite measurements and with lidar measurements of backscatter.

Jonsson, H. H.↗
NASA NTRS1994

Giotto ion mass spectrometer measurements at comet P/Grigg-Skjellerup

The Giotto ion mass spectrometer high-intensity spectrometer (IMS-HIS) measured fluxes of ions from about 260,000 km before (1008:37 UT spacecraft time) to about 86,000 km after (1701:33 UT spacecraft time) closest approach to comet P/Grigg-Skjellerup during the encounter on July 10, 1992. Although the HIS sensor was not designed to measure protons, these ions were measured far from the comet. Close in to the comet, the ions observed were probably also protons, although heavier ions cannot be completely ruled out. Considerable temporal structure appears in the data, well-correlated with the data of other instruments onboard, especially those of the magnetometer. In particular, the ion count rate correlates with the direction of the magnetic field. This strong modulation at the water group ion cyclotron period (approx. 90 s) inside the inbound bow wave indicates a very narrow ion pitch angle distribution. Hence at Grigg-Skjellerup the ions appear to experience very little pitch angle scattering. This may result from strong compression in the rapidly increasing magnetic field.

Goldstein, R.↗
NASA NTRS1993

Primary results from the Berkeley EUV airglow rocket spectrometer: O I and N2 FUV/EUV dayglow in the thermosphere and lower exosphere

The Berkeley extreme-ultraviolet airglow rocket spectrometer (BEARS) made spectroscopic measurements of far and extreme UV, atomic oxygen emissions from a Black Brandt XII (12.041 WT) sounding rocket launched from Wallops Island, Virginia, on September 30, 1988. BEARS' primary instrument, a near-normal Rowland mount spectrometer, measured several atomix oxygen and molecular nitrogen dayglow features at high spectral resolution (1.5 A): O I (989, 1027, 1304, and 1356 A); and N2 Lyman-Birge-Hopfield (4, 0) and (3, 0) bands at 1325 and 1354 A. The instrument collected over 800 s of data spanning altitudes of 150 - 963 km with look directions between 95 deg and 125 deg from zenith. We have analyzed the data using electrons and radiative transport models in a forward modeling approach. The model and data are generally in good agreement. However, there are some discrepancies, which are discussed in terms of remote sensing capabilities and improvements to the models.

Cotton, Daniel M.↗
NASA NTRS1995

Two-Diffraction-Order, Beam-Splitting, Imaging Spectrometer

Two-octave imaging spectrometer utilizes light of two harmonically related wavelengths diffracted to harmonically related orders at same angles, followed by separation via dichroic beam splitter before final imaging. Conceptual design of spectrometer calls for minimum number of optical elements to achieve coverage of required visible and near-infrared wavelengths in instrument of reduced size, weight, and cost.

Labaw, Clayton C.↗
NASA NTRS1995

Mass spectrometer measurements of test gas composition in a shock tunnel

Shock tunnels afford a means of generating hypersonic flow at high stagnation enthalpies, but they have the disadvantage that thermochemical effects make the composition of the test flow different to that of ambient air. The composition can be predicted by numerical calculations of the nozzle flow expansion, using simplified thermochemical models and, in the absence of experimental measurements, it has been necessary to accept the results given by these calculations. This note reports measurements of test gas composition, at stagnation enthalpies up to 12.5 MJ.kg(exp -1), taken with a time-of-flight mass spectrometer. Limited results have been obtained in previous measurements. These were taken at higher stagnation enthalpies, and used a quadruple mass spectrometer. The time-of-flight method was preferred here because it enabled a number of complete mass spectra to be obtained in each test, and because it gives good mass resolution over the range of interest with air (up to 50 a.m.a.).

Skinner, K. A.↗
NASA NTRS1996

Telescope With A Two-Color Camera And Two Imaging Spectrometers

Proposed remote-sensing optical instrument system includes two charge-coupled-device (CCD) video cameras sensitive to different colors of light; line-imaging infrared spectrometer; and line-imaging ultraviolet spectrometer; all sharing common telescope foreoptics. Principal advantages: compactness and light weight.

Chrisp, Michael P.↗
NASA NTRS1996

A visible-infrared imaging spectrometer for planetary missions

This final report summarizes the design effort for the construction of a visible-infrared imaging spectrometer for planetary missions, funded by NASA under the Planetary Instrument Definition and Development Program. The goal was to design and develop a prototype brassboard pushbroom imaging spectrometer covering the 0.35 gm to 2.5 gm spectral region using a simplified optical layout that would minimize the size, mass and parts count of the instrument by using a single holographic grating to disperse and focus light from a single slit onto both the infrared and visible focal plane arrays. Design approaches are presented and analyzed, along with problems encountered and recommended solutions to those problems. In particular, a new type of grating, incorporating two sets of rulings and a filter in a layered structure, is presented for further development.

McCord, Thomas↗
NASA NTRS1989

The Wavelength-Dispersive Spectrometer and Its Proposed Use in the Analytical Electron Microscope

The Analytical Electron Microscope (AEM) equipped with a wavelength-dispersive spectrometer (WDS) should have the ability to resolve peaks which normally overlap in the spectra from an energy-dispersive spectrometer (EDS). With a WDS it should also be possible to measure lower concentrations of elements in thin foils due to the increased peak-to-background ratio compared with EDS. The WDS will measure X-ray from the light elements (4 less than Z less than 1O) more effectively. This paper addresses the possibility of interfacing a compact WDS with a focussing circle of approximately 4 cm to a modem AEM with a high-brightness (field emission) source of electrons.

Goldstein, Joseph I.↗
NASA NTRS1997

Observing gamma-ray bursts with the INTEGRAL spectrometer SPI

The spectrometer for INTEGRAL (SPI) is a germanium spectrometer with a wide field of view and will provide the International Gamma Ray Astrophysics Laboratory (INTEGRAL) mission with the opportunity of studying gamma ray bursts. Simulations carried out to assess the response of the instrument using data from real burst data as input are reported on. It is shown that, despite the angular resolution of 3 deg, it is possible to locate the direction of bursts with an accuracy of a few arcmin, while offering the high spectral resolution of the germanium detectors. It is remarked that the SPI field of view is similar to the size of the halo of bursts expected around M 31 on galactic models. The detectability of bursts with such a halo is discussed.

Skinner, G. K.↗
NASA NTRS1997

Induced Background in the Mars Observer Gamma-Ray Spectrometer

Gamma-Ray Spectrometers in space must necessarily work in an environment of a background of lines due to natural and cosmic-ray induced radioactivity and lines due to prompt emission following nuclear reactions caused by primary and secondary cosmic rays. The Gamma-Ray Spectrometer (GRS) on the Mar Observer mission has provided important data allowing one to estimate for future missions the extent of the background due to cosmic rays. These data will help in the design of instruments and in calculation of realistic background intensities that may effect the sensitivity of determining the intensity of lines of interest.

Boynton, William V.↗
NASA NTRS1998

NEAR Gamma Ray Spectrometer Characterization and Repair

This report covers the work completed in the third year of the contract. The principle activities during this period were (1) the characterization of the NEAR 2 Gamma Ray Spectrometer using a neutron generator to generate complex gamma ray spectra and a large Ge Detecter to identify all the major peaks in the spectra; (2) the evaluation and repair of the Engineering Model Unit of the Gamma Ray Spectrometer for the NEAR mission; (3) the investigation of polycapillary x-ray optics for x-ray detection; and (4) technology transfer from NASA to forensic science.

Groves, Joel Lee↗
NASA NTRS1998

Alignment and Polarization Sensitivity Study for the Cassini-Composite InfraRed Spectrometer (CIRS) Far InfraRed (FIR) Interferometer

The Composite InfraRed Spectrometer (CIRS) instrument flying on the Cassini spacecraft to Saturn is a cryogenic spectrometer with far-infrared (FIR) and mid-infrared (MIR) channels. The CIRS FIR channel is a polarizing interferometer that contains three polarizing grid components. These components are an input polarizer, a polarizing beamsplitter, and an output polarizer/analyzer. They consist of a 1.5 micron thick mylar substrate with 2 gm wide copper wires, with 2 gm spacing (4 micron pitch) photolithographically deposited on the substrate. This paper details the polarization sensitivity studies performed on the output polarizer/analyzer, and the alignment sensitivity studies performed on the input polarizer and beamsplitter components in the FIR interferometer.

Crooke, Julie A.↗
NASA NTRS1998

Reference Interferometer Using a Semiconductor Laser/LED Reference Source in a Cryogenic Fourier-Transform Spectrometer

A combination of a single mode AlGaAs laser diode and broadband LED was used in a Michelson interferometer to provide reference signals in a Fourier transform spectrometer, the Composite Infrared Spectrometer, on the Cassini mission to Saturn. The narrowband light from the laser produced continuous fringes throughout the travel of the interferometer, which were used to control the velocity of the scan mechanism and to trigger data sampling. The broadband light from the LED produced a burst of fringes at zero path difference, which was used as a fixed position reference. The system, including the sources, the interferometer, and the detectors, was designed to work both at room temperature and instrument operating temperature of 170 Kelvin. One major challenge that was overcome was preservation, from room temperature to 170 K, of alignment sufficient for high modulation of fringes from the broadband source. Another was the shift of the source spectra about 30 nm toward shorter wavelengths upon cooldown.

Martino, Anthony J.↗
NASA NTRS1998

Effects of Shear, Defocus, and Wavefront Error on the Theoretical Performance of the Composite Infrared Spectrometer for Cassini

The combined effects on performance of shear between the two arms, defocus of die detector, and difference in wavefront between the two arms of a Fourier transform spectrometer using cube corner retroreflectors were investigated. Performance was characterized by the amplitude of the fringe signals coming from a detector as the path-length difference was scanned. A closed-form expression was found for the combined effects of shear and defocus, and it was found that defocus had no effect in the absence of shear. The effect of wavefront error was modeled numerically and assumed to be independent of shear and defocus. Results were compared with measurements made on the breadboard and engineering model of the Composite Infrared Spectrometer for the Cassini mission to Saturn, and good agreement was found.

Martino, Antonio J.↗