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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

EGRET High Energy Capability and Multiwavelength Flare Studies and Solar Flare Proton Spectra

UNH was assigned the responsibility to use their accelerator neutron measurements to verify the TASC response function and to modify the TASC fitting program to include a high energy neutron contribution. Direct accelerator-based measurements by UNH of the energy-dependent efficiencies for detecting neutrons with energies from 36 to 720 MeV in NaI were compared with Monte Carlo TASC calculations. The calculated TASC efficiencies are somewhat lower (by about 20%) than the accelerator results in the energy range 70-300 MeV. The measured energy-loss spectrum for 207 MeV neutron interactions in NaI were compared with the Monte Carlo response for 200 MeV neutrons in the TASC indicating good agreement. Based on this agreement, the simulation was considered to be sufficiently accurate to generate a neutron response library to be used by UNH in modifying the TASC fitting program to include a neutron component in the flare spectrum modeling. TASC energy-loss data on the 1991 June 11 flare was transferred to UNH. Also included appendix: Gamma-rays and neutrons as a probe of flare proton spectra: the solar flare of 11 June 1991.

Chupp, Edward L.↗
NASA NTRS2011

An Archean Biosphere Initiative

The search for life on extrasolar planets will necessarily focus on the imprints of biolgy on the composition of planetary atmospheres. The most notable biological imprint on the modern terrestrial atmosphere is the presence of 21 % O2, However, during most of the past 4 billion years, life and the surface environments on Earth were profoundly different than they are today. It is therefore a major goal of the astrobiology community to ascertain how the O2 content of the atmosphere has varied with time. and to understand the causes of these variations. The NAI and NASA Exobiology program have played critical roles in developing our current understanding of the ancient Earth's atmosphere, supporting diverse observational, analytical, and computational research in geoscience, life science, and related fields. In the present incarnation of the NAI, ongoing work is investigating (i) variations in atmospheric O2 in the Archean to the Cambrian, (ii) characterization of the redox state of the oceans shortly before, during and after the Great Oxidation Event (GOE), and (iii) unraveling the complex connections between environmental oxygenation, global climate, and the evolution of life.

Anbar, A. D.↗
NASA NTRS2017

NExSS/NAI Joint ExoPAG SAG 16 Report on Remote Biosignatures for Exoplanets

Future exoplanet observations will soon focus on the search for life beyond the Solar System. Exoplanet biosignatures to be sought are those with global, potentially detectable, impacts on a planet. Biosignatures occur in an environmental context in which geological, atmospheric, and stellar processes and interactions may work to enhance, suppress or mimic these biosignatures. Thus biosignature scienceis inherently interdisciplinary. Its advance is necessary to inform the design of the next flagship missions that will obtain spectra of habitable extrasolar planets. The NExSS NAI Joint Exoplanet Biosignatures Workshop Without Walls brought together the astrobiology, exoplanet, and mission concept communities to review, discuss, debate, and advance the science of remote detection of planetary biosignatures. The multi-meeting workshop began in June 2016, and was a process that engaged a broad range of experts across the interdisciplinary reaches of NASA's Nexus for Exoplanet System Science (NExSS) program, the NASA Astrobiology Institute (NAI), NASAs Exoplanet Exploration Program (ExEP), and international partners, such as the European Astrobiology Network Association (EANA) and Japans Earth Life Science Institute (ELSI). These groups spanned expertise in astronomy, planetary science, Earth sciences, heliophysics, biology, instrument mission development, and engineering.

Kiang, Nancy Y.↗
NASA NTRS2019

Interdisciplinary Studies of a Marine Microbial Mat Ecosystem, Baja California, Mexico

Cyanobacterial mats in extensive seawater evaporation ponds at Guerrero Negro, Baja California, Mexico, have been excellent subjects for interdisciplinary research. Exportadora de Sal, S.A. (ESSA) has maintained this solar saltern since the 1950s. The following entities provided research support: NASA Exobiology (1984-1988), Precambrian Paleobiology Research Group (1986-1993), NAI (1998-2010), and Exobiology (2010-2016). This summary emphasizes research that was supported by the NAI and conducted by its teams.

Des Marais, David J.↗
NASA NTRS1972

The measurement of radiation exposure of astronauts by radiochemical techniques

The principal gamma-ray emitting radioisotopes, produced in the body of astronauts by cosmic-ray bombardment, which have half-lives long enough to be useful for radiation dose evaluation, are Be-7, Na-22, and Na-24. The sodium isotopes were measured in the preflight and postflight urine and feces, and those feces specimens collected during the manned Apollo missions, by analysis of the urine salts and the raw feces in large crystal multidimensional gamma-ray spectrometers. The Be-7 was chemically separated, and its concentration measured in an all NaI (TL), anticoincidence shielded, scintillation well crystal. The astronaut radiation dose in millirads, as determined for the Apollo 7, 8, 9, 10, 11, 12, and 13 missions, was 330, 160, smaller than 315, 870 plus or minus 550, 31, 110, and smaller than 250, respectively.

Brodzinski, R. L.↗
NASA NTRS1971

Modification of codes NUALGAM and BREMRAD, Volume 1

The NUGAM2 code predicts forward and backward angular energy differential and integrated distributions for gamma photons and fluorescent radiation emerging from finite laminar transport media. It determines buildup and albedo data for scientific research and engineering purposes; it also predicts the emission characteristics of finite radioisotope sources. The results are shown to be in very good agreement with available published data. The code predicts data for many situations in which no published data is available in the energy range up to 5 MeV. The NUGAM3 code predicts the pulse height response of inorganic (NaI and CsI) scintillation detectors to gamma photons. Because it allows the scintillator to be clad and mounted on a photomultiplier as in the experimental or industrial application, it is a more practical and thus useful code than others previously reported. Results are in excellent agreement with published Monte Carlo and experimental data in the energy range up to 4.5 MeV.

Steyn, J. J.↗
NASA NTRS1972

A versatile Mossbauer spectrometer and its applications in vibration measurement

A Fe-57 Mossbauer spectrometer, equally efficient in transmission and reflection geometries, is described. The radiation detector consists of a 1.524- by 5.08 by 5.08-cm rectangular NaI(Tl) crystal with a hole 1.524 cm in diameter. The front and back faces of the crystal are covered with beryllium windows 0.0127 cm thick and 3.81 cm in diameter. The energy of the radiation accepted for counting ranges from 6.3 keV conversion X-rays to the 14.4 keV reemitted gamma rays. The spectrometer was used to measure various types of low frequency (10 Hz) and low amplitude (0.254 mm) periodic motion of steel specimens.

Singh, J. J.↗
NASA NTRS1971

A gamma ray monitor for the OSO-7 spacecraft

A 3 in. x 3 in. NaI(Tl) gamma ray (0.3 to 10 MeV) spectrometer with a CsI(Na) charged particle and anti-Compton shield has been developed for the Orbiting Solar Observatory (OSO-7) which was launched September 30, 1971. The instrument, designed for a rotating wheel compartment, utilizes a 377 channel quadratic PHA with accumulation times of 3, 1, or 0.5 minutes. Quick look and calibration data obtained via a direct data link to a minicomputer allows near real time monitoring and control of the experiment. Various commands changing the operating mode can be executed. The functions which can be commanded include: rotation of the quadrants in which data is collected by 90 deg; gain adjustment of the central detector over a 6:1 range; manual or automatic sequencing of calibrations; variations of accumulation times by telemetering selected channels; and selection of reference directions. A small X-ray detector covering the range 7.5 to 120 keV is also included.

Higbie, P. R.↗
NASA NTRS1972

A gamma ray monitor for the OSO-7 spacecraft.

A NaI(T2) gamma ray spectrometer with a CsI(Na) charged particle and anti-Compton shield has been developed for the spacecraft. The spacecraft telemetry system employs a 800 Hz clock and reads data out on a basic 32-word (byte) Main Frame cycle. The data from the instrument include spectral data, X-ray data, and housekeeping data. The gamma ray pulses from the anode of the central detector flow through the front end electronics, where they are amplified by a charge sensitive preamplifier. The admission of the desired gamma ray into the data stream is controlled by a linear gate.

Higbie, P. R.↗
NASA NTRS1972

The cosmic gamma-ray spectrum between 0.3 and 27 MeV measured on the Apollo 15

The spectrum of the total (diffuse and discrete sources) cosmic gamma-ray background over the 0.3 to 27 MeV range was measured with a 7.0 cm diameter x 7.0 cm long uncollimated NaI(Tl) scintillation counter located on a boom 7.6 m from the Apollo 15 service module. Data on cosmic gamma-rays were taken during transearth coast at various boom extensions, detector gains, and with the plastic anticoincidence scintillator enabled and disabled.

Trombka, J. I.↗
NASA NTRS1973

Spectrum of atmospheric gamma rays to 10 MeV at lambda = 40 deg

Results of measurements of the differential counting rate spectra due to atmospheric gamma rays as a function of altitude to 3.6 g/sq cm over Texas. Two gain settings and a 128-channel pulse height analyzer were used to cover the range from 0.2 to 10 MeV. The detector was a 7.6 x 7.6 cm NaI crystal, which was surrounded on five sides by a 2-cm-thick plastic anticoincidence shield for charged particle rejection. The system had a nearly isotropic response to photons above 0.2 MeV. The spectrum at ceiling appeared as a steep continuum with a power-law index of about 1.4. The only obvious feature was the 0.51-MeV positron annihilation line. The spectral shape was independent for depths less than 20 g/sq cm, the absolute intensity varying in proportion to the intensity of the cosmic ray secondary charged particles. Also, at depths less than 30 g/sq cm the observed flux variation with altitude can be described in terms of an empirical depth-dependent source function.

Peterson, L. E.↗
NASA NTRS1974

Search for gamma ray lines from supernovae and supernova remnants

A gamma ray monitor with a NaI crystal shielded with a cup-shaped CsI cover was contained in the rotating wheel compartment of the OSO-7 spacecraft for measuring the gamma ray spectra from 0.3 to 10 MeV in search for gamma ray lines from a possible remnant in the Gum Nebula and the apparent Type I supernovae in NGC5253. A brief analysis of data yielded no positive indications for X-rays, gamma ray lines, or continuum from these sources.

Chupp, E. L.↗
NASA NTRS1974

Measurements of the 0.1-27 MeV cosmic gamma ray spectrum by Apollos 15 and 16

The spectrum of diffuse cosmic gamma rays over the 0.127 MeV range was measured by a 7 x 7 cm omnidirectional NaI counter on Apollo 15 and 16. Location of the spectrometer on a 7.6 m extensible boom, use of precision pulse-height analysis, and operation in several modes permitted data to be obtained from which spacecraft and other background contributions could be separated. Recent measurements verified the Apollo spectrum.

Peterson, L. E.↗
NASA NTRS1974

The UCSD/MIT hard X-ray and low energy gamma ray experiment for HEAO-A

An HEAO-A spacecraft is described which is scheduled for launch in April 1977 to survey the sky in the 0.15 keV to 10 MeV range of X-rays with improved sensitivity and angular resolution. The spectral and time variations of discrete sources, and the spectrum and isotropy of the diffuse component will be measured. A hard X-ray and low energy gamma ray experiment is described which will use as an array of seven (NaI)(Tl)/CsI(Na) phoswich detectors and eight large CsI(Na) shields. Detector events are pulse-height analyzed with a selectable time resolution of 0.1, 0.005, or 0.00002 sec. The instrument background is expected to be comprised of approximately equal parts of diffuse gamma rays entering the aperture, radioactive decay of spallation products, and gamma ray leakage through the shields. Detailed background predictions are presented, and sensitivity estimates indicate that the Crab nebula should be detected up to approximately 5 MeV. Approximate 1% isotropy limits for the diffuse component of cosmic gamma rays should be achieved, and its spectrum measured with improved precision.

Matteson, J. L.↗