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NASA NTRS1981

Cosmic ray detector for high energy iron nuclei

An experiment to directly measure the differential energy spectra of nuclei with charge between 15-28 inclusive with a balloon borne instrument is presented. A High Energy Gas Cerenkov Spectrometer (HEGCS) is described, and consists of a 3 m diam drum 4.5 m tall containing three light diffusion chambers. A hodoscopic array of scintillators emit light into the top and bottom light chambers which serve for track recordings of the trajectory and charge of incident cosmic rays. A center chamber pressure vessel, the HEGCS, has a 4.0 m sr and a threshold of 50 GeV/amu. The hexagonal array scintillators have 24 elements/array feeding photomultiplier tubes at the vertices between the scintillators, with other PMTs located around the top and bottom chambers to capture escaped scintillator light. The HEGCS is filled with freon-12, with reflective paint on the inner surface to convert UV Cerenkov photons into visible photons near 425 nm.

Streitmatter, R. E.↗

NASA NTRS1982

Laboratory studies of UV emissions of H2 by electron impact - The Werner- and Lyman-band systems

The vacuum ultraviolet electron-impact-induced fluorescence emissions of H2 were studied for the Lyman and Werner band systems in the range of 120-170 nm, using an optical system containing a photomultiplier and a spectrometer, over an energy range from threshold to 400 eV. The emission cross sections for the Lyman and Werner transitions at 100 eV are determined. The cross-section ratio is in excellent agreement with theoretical calculations and experimental data for the optical oscillator strengths. The cross-section for cascading to the B state is stated as a percentage of the total emission cross section at both 100 and 300 eV, increasing substantially at 20 eV. The vibrational population distribution of the B state is found to be a function of electron-impact energy as the importance of cascading relative to direct excitation changes with electron-impact energy.

Ajello, J. M.↗

NASA NTRS1982

Ultraheavy cosmic rays - HEAO-3 results

The instrumentation and results from the Heavy Nuclei experiment on the HEAO 3 satellite are described. Six independently analyzed dual-gap ionization chambers measured the energy loss of the cosmic rays while a Cerenkov counter with 8 independently analyzed photomultipliers viewed two sheets of Pilot 425 plastic in a white box. Trajectories of the cosmic ray nuclei were determined in multiwire ionization hodoscopes. Variations in abundances were observed to be imperfectly ordered in terms of the first ionization potential, and volatility was also ruled out as the controlling factor. A predicted drop in abundance after Ba-56 was found, along with another sharp fall above Pb-82. Only one actinide-type event was detected during the 14 mos of viewing, a result consistent with other findings but which testifies against r-process formation.

Israel, M. H.↗

NASA NTRS1981

The heavy nuclei experiment on HEAO-3

The HEAO-3 experiment to study the heavy and ultraheavy nuclei in cosmic radiation is described. The array is double-ended and consists of three main elements. Two pressure chambers, filled with an argon-methane mixture at about 850 torr, each contain two x-y hodoscopes made of wires spaced 1 cm apart and three parallel plate ionization chambers. Between the pressure chambers is mounted a Cerenkov counter composed of two layers of Pilot 425 radiator looked at by eight photomultipliers. The instrument is designed to achieve a charge resolution of 0.3 charge units over the charge range 17-120, which requires a measurement accurate to 0.6 percent at Z = 100. Examination of selected data shows that the instrument has the intrinsic resolution needed.

Binns, W. R.↗

NASA NTRS1982

Application of upconversion detection to pulsed CO2 lidar

In this paper the application of an upconversion detector to pulsed CO2 lidar is investigated. In this device a nonlinear IR crystal would be used to convert 10-micron lidar radiation into the visible region for conventional detection with a photomultiplier tube. A pulsed CO2 lidar can be substantially improved with an upconversion detector configured for rejection of thermal background radiation using a narrowband filter for the upconverted signal or a cold filter front end. The sensitivity of the upconversion detector with the narrowband visible wavelength filter is estimated to be 2 orders of magnitude better than that of the usual direct detection diode. The cold filter can improve upconversion detection to nearly the signal-shot limit. These upconversion detectors are not limited by speckle noise as is a pulsed heterodyne detector.

Itabe, T.↗

NASA NTRS1983

Development of a simplified optical technique for the simultaneous measurement of particle size distribution and velocity

Existing techniques were surveyed, an experimental procedure was developed, a laboratory test model was fabricated, limited data were recovered for proof of principle, and the relationship between particle size distribution and amplitude measurements was illustrated in an effort to develop a low cost, simplified optical technique for measuring particle size distributions and velocities in fluidized bed combustors and gasifiers. A He-Ne laser illuminated Rochi Rulings (range 10 to 500 lines per inch). Various samples of known particle size distributions were passed through the fringe pattern produced by the rulings. A photomultiplier tube converted light from the fringe volume to an electrical signal which was recorded using an oscilloscope and camera. The signal amplitudes were correlated against the known particle size distributions. The correlation holds true for various samples.

Smith, J. L.↗

NASA NTRS1983

Approximation to the Probability Density at the Output of a Photmultiplier Tube

The probability density of the integrated output of a photomultiplier tube (PMT) is approximated by the Gaussian, Rayleigh, and Gamma probability densities. The accuracy of the approximations depends on the signal energy alpha: the Gamma distribution is accurate for all alpha, the Raleigh distribution is accurate for small alpha (approximate or less than 1 photon) and the Gaussian distribution is accurate for large alpha (approximate or greater than 10 photons).

Stokey, R. J.↗

NASA NTRS1983

TM report

Key spectral, radiometric, and geometric characteristics of the TM sensor are examined. Spectrally, band 5 is slightly wider than specified and its upper edge at 50% of miximum of 1784 nm includes some unintended overlap with water absorption bands. Thermal band 6 is half the expected width. Radiometrically, the TM has extreme linearity and stability in comparison with previous MSS photomultiplier systems. Forward and reverse scans on TM show some unexplained radiometric differences of up to four digital levels. Primary focal plane bands show a monotomic decrease in gain of about 5% in the five months since launch. The relative internal gains of bands 5 and 7 varied with a period of about 60 days and an amplitude of about 6%. Radiometric calibration must be applied before histogram equalization algorithms to preserve radiometric accuracy. Geometrically, channel 4 in band 2 has a smaller modulation transfer function than desired. There is apparent misregistration of .75 pixels along scan and 0.2 pixels across scan.

Barker, J. L.↗

NASA NTRS1981

Multispectral scanner, thematic mapper, and beyond

The capabilities and functions of the Landsat D multispectral scanner (MSS) and thematic mapper (TM) are explored as a basis for improvements to satisfy increasing user demands. The MSS is an object-space line scanner for gathering data in four spectral bands ranging from 0.5-1.1 micron. In a 705 km near-polar sunsynchronous orbit, the MSS will generate 185 x 185 km imagery with 80 x 80 m ground resolution, mapping the entire earth every 16 days. Photomultiplier tubes are used for four of the bands and the other employs Si photodiodes. A calibration light source provides in orbit calibration during every reverse scan period of a pivotal on-board mirror. The TM collects data in seven bands from 0.45-12.5 microns, yielding a ground resolution of 30 x 30 m in six bands for reflected sunlight and 120 x 120 m for the 10.4-12.5 thermal bands. The addition of 16 Si detectors for 0.9-1.1 micron viewing for agricultural purposes, as well as higher resolution, is discussed.

Jones, C. R.↗

NASA NTRS1981

Satellite laser altimeter for measurement of ice sheet topography

Results of a preliminary conceptual design study are presented for a laser altimeter that is capable of high-resolution mapping of the polar ice sheets and is proposed for inclusion in the National Oceanic Satellite System spacecraft or other polar-orbiting satellites. The instrument consists of a pulsed-laser transmitter operating at a wavelength of 532 nm and a duration of 5 nsec, a receiver telescope, a photomultiplier-tube detector, data processing and control electronics, and an attitude sensing and measurement system; a laser footprint diameter of 70 m is planned. The altimeter components are described, and the accuracy of both the altimetry measurement and the attitude measurement is evaluated. A range precision of about 10 cm is estimated, along with an attitude measurement accuracy of approximately 10 arcsec.

Bufton, J. L.↗

NASA NTRS1982

The eight-color asteroid survey - Standard stars

Compositionally diagnostic information regarding the spectral reflectance of faint asteroids and planetary satellites, obtained using a photometric system, is presented. Standard UBV and range in effective wavelength from 0.34 to 1.04 microns are among the eight broadband filters relative to the study. An InGaAsP photomultiplier of high quantum efficiencies employed for longer wavelengths, allows work to magnitude 17 and fainter when used in conjunction with a 2 m telescope. Magnitudes and color indices with mean uncertainty + or - 0.006 mag for 50 standard stars are presented, and by setting the mean colors of four of these stars to zero, the zero point of the system is established. Sun color implications resulting from the study are U-B = 0.20 + or - 0.02, and B-V = 0.67 + or - 0.02.

Tedesco, E. F.↗

NASA NTRS1983

NASA multipurpose airborne DIAL system and measurements of ozone and aerosol profiles

The hardware, operational characteristics, data processing system, and applications of the NASA airborne differential absorption lidar (DIAL) system are described. DIAL functions by assessing the average gas concentration over a specified range interval by analyzing the difference in lidar backscatter signals for laser wavelengths tuned on and off of the molecular absorption line of a gas under investigation. The system comprises two frequency-doubled Nd:YAG lasers pumping two high conversion efficiency tunable dye lasers emitting pulses separated by 100 microsec or less. The return signals are digitized and stored on magnetic tape. The signal collector consists of photomultiplier tubes implanted in a cassegrain telescope. Flight tests of the system involved on-measurements at 285.95 nm and off-measurements at 299.40 nm, which yielded a differential cross section of 1.74 x 10 to the -16th sq cm. In situ measurements with another plane at a nominal altitude of 3.2 km for comparison purposes showed accuracy to within 10% in and above the boundary layer. The system is considered as a test apparatus for more developed versions to be flown on the Shuttle

Browell, E. V.↗

NASA NTRS1983

Gamma ray detection with long NaI/Tl/ scintillator bars

Test measurements with a prototype NaI(Tl) scintillator for energy, position, and timing measurements in gamma ray astronomy are reported. The scintillator bar is 100 x 5 x 5 cu cm in size, and allows detection of the arrival times and pulse heights of signals from two photomultiplier tubes, one at each end of the bar. Data is gathered on the energy loss, linear position, and time-of-flight of gamma ray interactions within the bar over an energy range of 0.5-20 MeV. A mean attenuation coefficient of 0.015/cm has been determined, as have a FWHM resolution of 5 cm, 9.4%, and 10 nsec at an energy of 0.662 MeV. At 1.25 MeV the timing resolution was 6 nsec, and at 6.13 MeV the spatial resolution was 2.2 cm. The instrument is a prototype of a Compton scatter telescope being constructed for two balloon flights, one each in the Northern and Southern Hemispheres, in 1984.

Zych, A. D.↗

NASA NTRS1982

New two-dimensional photon camera

A photon-sensitive camera, applicable to speckle imaging of astronomical sources, high-resolution spectroscopy of faint galaxies in a crossed-dispersion spectrograph, or narrow-band direct imaging of galaxies, is presented. The camera is shown to supply 8-bit by 8-bit photon positions (256 x 256 pixels) for as many as 10 to the 6th photons/sec with a maximum linear resolution of approximately 10 microns. The sequence of photon positions is recorded digitally with a VHS-format video tape recorder or formed into an immediate image via a microcomputer. The four basic elements of the camera are described in detail: a high-gain image intensifier with fast-decay output phosphor, a glass-prism optical-beam splitter, a set of Gray-coded masks, and a photomultiplier tube for each mask. The characteristics of the camera are compared to those of other photon cameras.

Papaliolios, C.↗

NASA NTRS1983

Classification of the Allan Hills A77307 meteorite

Thermoluminescence (TL) measurements on Allan Hills A77307 (AH), a carbonaceous chondrite found in Antarctica, are compared with those on other chondrite and applied to its classification. Two lithologically different 250-mg samples were ground, freed of magnetic material, and ground again to pass a 100-micron sieve. Aliquots of 4 mg were heated to 500 C, exposed to beta radiation from a Sr-90 source, and heated at a rate of 7.3 C/sec in N2. TL was measured with a photomultiplier tube fitted with thermal and blue filters. Glow curves for AH and for seven other, established CO-type chondrites area presented, all exhibiting two major peaks of TL sensitivity. The peaks for the seven CO-type chondrites are found at 91 + or - 7 C and at 203 + or - 11 C; those for AH at 170 + or - 17 C and at approximately 250 C. This difference is considered significant and not due to random fluctuation or a typical sampling. From this comparison and from consideration of the weathering, preterrestrial-alteration, petrological and compositional evidence on AH, it is concluded that AH is a unique chondrite, possessing both similarities to and differences from the CO class.

Sears, D. W. G.↗

NASA NTRS1983

Transition probability of the Si III 189.2-nm intersystem line

Measurement of the lifetime of the metastable 3s3p(3)P(0)1 level of Si(2+) (Si III), which decays by photon emission at 189.2 nm to the 3s2(1)S0 state, is reported. The data were taken from spontaneous emission from metastable Si III stored in an RF ion trap. The Si III ions were produced through electron bombardment of SiH4 and SiF4 at pressures of 1/100,000,000-1/10,000,000 Torr. A photomultiplier was employed to count the photon emissions from the transitions. A total of 11 decay curves were generated for analysis, with Poisson statistics used to set the uncertainties at within 8 pct. Significant systematic effects were controlled, and the lifetime was found to be within 3.6 microsec of 59.9 microsec. The method used is concluded valid for determining the lifetimes of metastable levels of low-Z ions with low charge, and thereby the transition probabilities.

Kwong, H. S.↗

NASA NTRS1983

Remote sensing of tropospheric gases and aerosols with airborne DIAL system

The multipurpose airborne DIAL system developed at NASA Langley Research Center is characterized, and the published results of tropospheric O3, H2O, and aerosol-backscatter remote-sensing experiments performed in 1980 and 1981 are summarized. The system comprises two tunable dye lasers pumped by frequency-doubled Nd:YAG lasers, dielectric-coated steering optics, a 36-cm-diameter Cassegrain receiver telescope, gateable photomultiplier tubes, and a minicomputer data-processing unit for real-time calculation of gas concentrations and backscattering profiles. The transmitted energy of the 100-microsec-separated dye-laser pulses is 40, 80, or 50 mJ/pulse at around 300, 600, or 720-nm wavelength, respectively. Good agreement was found between DIAL-remote-sensed and in-situ H2O and O3 profiles of the lower troposphere and O3 profiles of the tropopause region, and the usefulness of DIAL backscattering measurements in the study of boundary-layer and tropospheric dynamics is demonstrated. The feasibility of DIAL sensing of power-plant or urban plume SO2, of urban-area (or rural-area column-content) NO2, and of temperature and H2O (simultaneously using a third laser) has been suggested by simulation studies.

Browell, E. V.↗

NASA NTRS1985

Optical Quantum Receiver For Binary Signals

In quantum optical receiver, both amplitude and phase of received optical signal measured to extract as much information as possible, thereby reducing error probability. Phase-modulated received signal mixed with equal amplitude replica of optical carrier generated in phase locked loop. Two signals interfere with each other at photomultiplier cathode. Probability of error with this scheme close to theoretical minimum and implemented with current technology.

Vilnrotter, V. A.↗