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NASA NTRS1976

Proton and deuteron double differential cross sections at angles from 10 deg to 60 deg from Be, C, Al, Fe, Cu, Ge, W, and Pb under 558-MeV-proton irradiation

The double differential cross sections for the production of protons and deuterons from targets of Be, C, Al, Fe, Cu, Ge, W, and Pb were obtained at laboratory angles of scatter of 10, 20, 30, 40, 50, and 60 degrees for 558-MeV incident protons. The position of the quasi-elastic peak, discernible in the cross sections up to approximately 40 degrees, corresponded closely to the theoretical predictions for proton-proton elastic scattering at 558 MeV. The mean ratio of deuteron to proton energy-integrated cross sections was 0.056 + or - 0.008. The dependence of energy-integrated cross sections for both protons and deuterons on target mass number A varied from A to the 1/3 power at 10 degrees to A to the 2/3 power above approximately 30 degrees. The ratio of energy-integrated deuteron cross sections for quasielastic processes to that for reactions yielding a deuteron-pi-meson pair was approximately 10 percent.

Beck, S. M.↗

NASA NTRS1976

A 0.4 to 10 GHz airborne electromagnetic environment survey of USA urban areas

An airborne electromagnetic-environment survey of some U.S. metropolitan areas measured terrestrial emissions within the broad frequency spectrum from 0.4 to 10 GHz. A Cessna 402 commercial aircraft was fitted with both nadir-viewing and horizon-viewing antennas and instrumentation, including a spectrum analyzer, a 35 mm continuous film camera, and a magnetic tape recorder. Most of the flights were made at a nominal altitude of 10,000 feet, and Washington, D. C., Baltimore, Philadelphia, New York, and Chicago were surveyed. The 450 to 470 MHz land-mobile UHF band is especially crowded, and the 400 to 406 MHz space bands are less active. This paper discusses test measurements obtained up to 10 GHz. Sample spectrum analyzer photograhs were selected from a total of 5,750 frames representing 38 hours of data.

Taylor, R. E.↗

NASA NTRS1976

Stark broadening of Balmer lines in the density range /2-8/ x 10 to the 14/cu cm

Experimental profiles of the hydrogen Balmer lines (H gamma-H sub 10) have been measured over the density range (2-8) x 10 to the 14/cu cm and compared with theoretical profiles. Electron densities were measured using a multipass interferometer, while plasma homogeneity was demonstrated using a Langmuir probe. Electron temperatures were in the range 1-2.0 eV. The electron density as deduced from line profiles tended to be as much as 10% lower than that from the interferometer at higher densities. At lower densities, the two methods agreed to within experimental error. Evidence for asymmetries on the line wings was noted.

Bengtson, R. D.↗

NASA NTRS1976

The S sub 10 /V/ unit of surface brightness

Some discrepancies in the use of the unit of zodiacal light measurements - S sub 10 (V), which is the equivalent number of tenth magnitude stars of solar spectral type per square degree - are discussed. It is suggested that: (1) the S sub 10 (V) unit be understood to represent 10th magnitude solar (G2V) stars per square degree at mean solar distance, (2) the V refers to the visual color in the UBV system defined by Johnson and Morgan (1953), (3) the apparent solar visual magnitude be taken as -26.73 and the B-V index as .63, (4) the solar spectral irradiance values of Labs and Neckel (1970) be used, and (5) when using Vega as a standard to obtain brightnesses in S sub 10 (V), +.04 be used as its magnitude at all wavelengths and the irradiance values of Hayes and Latham (1975) be used.

Sparrow, J. G.↗

NASA NTRS1977

Altimeter error sources at the 10-cm performance level

Error sources affecting the calibration and operational use of a 10 cm altimeter are examined to determine the magnitudes of current errors and the investigations necessary to reduce them to acceptable bounds. Errors considered include those affecting operational data pre-processing, and those affecting altitude bias determination, with error budgets developed for both. The most significant error sources affecting pre-processing are bias calibration, propagation corrections for the ionosphere, and measurement noise. No ionospheric models are currently validated at the required 10-25% accuracy level. The optimum smoothing to reduce the effects of measurement noise is investigated and found to be on the order of one second, based on the TASC model of geoid undulations. The 10 cm calibrations are found to be feasible only through the use of altimeter passes that are very high elevation for a tracking station which tracks very close to the time of altimeter track, such as a high elevation pass across the island of Bermuda. By far the largest error source, based on the current state-of-the-art, is the location of the island tracking station relative to mean sea level in the surrounding ocean areas.

Martin, C. F.↗

NASA NTRS1977

Observations of 10-eV to 25-keV electrons in steady diffuse aurora from Atmosphere Explorer C and D

Electron energy spectra from 10 eV to 25 keV have been obtained from steady diffuse auroral forms at altitudes above 150 km by the Atmosphere Explorer C and D spacecraft. Overlapping coverage of the energy range was provided by the photoelectron spectrometer experiment (10-500 eV) and the low-energy electron experiment (0.2-25 keV). The spectral shape between 10 and 20 eV is independent of altitude between 150 and 270 km, has variable energy dependence between about 20 and 150 eV, and above approximately 150 eV has energy dependence determined primarily by the details of the energy spectrum of electrons incident on the atmosphere. The observed results are in satisfactory agreement with two recently published model calculations.

Peterson, W. K.↗

NASA NTRS1977

Pioneer 9 and Pioneer 10 observations of the solar wind associated with the August 1972 events

Observations are presented of the changes in the solar wind proton parameters at 0.8 and 2.2 AU as a result of the solar flares in August 1972. These observations were obtained by the NASA Ames Research Center solar wind plasma analyzer experiments on Pioneer 9 and Pioneer 10. High time resolution measurements are presented of the solar wind proton speed associated with the arrival of the interplanetary shocks at Pioneer 9 and Pioneer 10. For these events, differential ion energy per unit charge spectra are shown which indicate the changes in the solar wind ion distribution function associated with the arrival of each of the interplanetary shocks. Four fast shocks are identified at Pioneer 9, and it is found that previously the time of arrival of the first interplanetary shock at Pioneer 9 was not correctly identified. Two fast shocks and one reverse shock are identified at Pioneer 10.

Intriligator, D. S.↗

NASA NTRS1976

0.4- to 10-GHz airborne electromagnetic-environment survey of United States urban areas

An airborne electromagnetic-environment survey of some U.S. metropolitan areas measured terrestrial emissions within the broad-frequency spectrum from 0.4 to 10 GHz. A Cessna 402 commercial aircraft was fitted with both nadir-viewing and horizon-viewing antennas and instrumentation, including a spectrum analyzer, a 35-mm continuous-film camera, and a magnetic-tape recorder. Most of the flights were made at a nominal altitude of 10,000 ft, and Washington, Baltimore, Philadelphia, New York, and Chicago were surveyed. The 450- to 470-MHz land-mobile UHF band is especially crowded, and the 400- to 406-MHz space bands are less active. Test measurements obtained up to 10 GHz are discussed. Sample spectrum-analyzer photographs were selected from a total of 5750 frames representing 38 hours of data.

Taylor, R. E.↗

NASA NTRS1977

10-deg off-axis test for shear properties in fiber composites

A combined theoretical and experimental investigation was conducted to assess the suitability of the 10-deg off-axis tensile test specimen for the intralaminar shear characterization of unidirectional composites. Composite mechanics, a combined-stress failure criterion, and a finite-element analysis were used to determine theoretically the stress-strain variation across the specimen width and the relative stress and strain magnitudes at the 10-deg plane. Strain gages were employed to measure the strain variation across the specimen width at specimen midlength and near the end tabs. Specimens from Mod-I/epoxy, T-300/epoxy, and S-glass/epoxy were used in the experimental program. It was found that the 10-deg off-axis tensile test specimen is suitable for intralaminar shear characterization, and it is recommended that it should be considered as a possible standard test specimen for such a characterization.

Chamis, C. C.↗

NASA NTRS1977

SAS-2 observations of the diffuse gamma radiation in the galactic latitude interval from 10 to 90 deg in both hemispheres

An analysis of all the second Small Astronomy Satellite (SAS-2) gamma-ray data for galactic latitudes higher than 10 deg in both hemispheres has shown that the intensity varies with galactic latitude, being larger near 10 deg than 90 deg. For energies above 100 MeV the gamma-ray data are consistent with a latitude distribution of the form I(b) = C1 + C2/sin b, with the second term being dominant. This result suggests that the radiation above 100 MeV is coming largely from local regions of the galactic disk. Between 35 and 100 MeV, a similar equation is also a good representation of the data, but here the two terms are comparable. These results indicate that the diffuse radiation above 35 MeV consists of two parts, one with a relatively hard galactic component and the other an isotropic steep spectral component which extrapolates back well to the low-energy (less than 10 MeV) diffuse radiation. The steepness of the diffuse isotropic component places significant constraints on possible theoretical models of this radiation.

Fichtel, C. E.↗

NASA NTRS1977

Mercury's helium exosphere after Mariner 10's third encounter

From Mariner 10 third encounter UV data, a value of .00045 was calculated as the fraction of the solar wind He++ flux intercepted and captured by Mercury's magnetosphere if the observed He atmosphere is maintained by the solar wind. If an internal source for He prevails, the corresponding upper bound for the global outgassing rate is estimated to be 4.5 x 10 to the 22nd power per sec. A surface temperature distribution was used which satisfies the heat equation over Mercury's entire surface using Mariner 10 determined mean surface thermal characteristics. The means stand off distance of Mercury's magnetopause averaged over Mercury's orbit was also used.

Curtis, S. A.↗

NASA NTRS1978

Pioneer 10 observation of the solar wind proton temperature heliocentric gradient

Solar wind isotropic proton temperatures as measured out to 12.2 AU heliocentric distance by the Ames plasma analyzer aboard Pioneer 10 are presented as consecutive averages over three Carrington solar rotations and discussed. The weighted least-squares fit of average temperature to heliocentric radial distance, R, yields the power law R sup -.52. These average proton temperatures are not correlated as well with Pioneer 10's heliocentric radial distance (-.85) as are the corresponding average Zurich sunspot numbers R sub z (-.95). Consequently, it is difficult to isolate the spatial gradient in the Pioneer 10 solar wind proton temperatures using that data alone.

Mihalov, J. D.↗

NASA NTRS1977

Pioneer 10 and 11 radio occultations by Jupiter

Results on the temperature structure of the Jovian atmosphere are reviewed which were obtained by applying an integral inversion technique combined with a model for the planet's shape based on gravity data to Pioneer 10 and 11 radio-occultation data. The technique applied to obtain temperature profiles from the Pioneer data consisted of defining a center of refraction based on a computation of the radius of curvature in the plane of refraction and the normal direction to the equipotential surface at the closest approach point of a ray. Observations performed during the Pioneer 10 entry and exit and the Pioneer 11 exit are analyzed, sources of uncertainty are identified, and representative pressure-temperature profiles are presented which clearly show a temperature inversion between 10 and 100 mb. Effects of zonal winds on the reliability of radio-occultation temperature profiles are briefly discussed.

Kliore, A. J.↗

NASA NTRS1978

Mercury's helium exosphere after Mariner 10's third encounter

From a comparison of the Mariner 10 third encounter UV spectrometer data with intensities generated from a newly constructed model exosphere, a new value of 4.5 x 10 to the -4th power for the fraction of the solar wind He(++) flux to be intercepted and captured by Mercury's magnetosphere, if the observed He atmosphere is maintained by the solar wind, has been derived. If an internal source for He prevails, the corresponding upper bound for the global outgassing rate is estimated to be 4.5 x 10 to the 22nd power/s. These values differ from those given earlier because of the present use of a surface temperature distribution satisfying the heat equation over Mercury's entire surface which employs Mariner-10-determined mean surface thermal characteristics. The mean standoff distance of Mercury's magnetopause averaged over Mercury's orbit is also used. Agreement between the observed and calculated intensities is found to be good. Minor discrepancies on the nightside of the terminator are explicable in terms of differences between actual and computed temperatures and scale height structure changes.

Curtis, S. A.↗

NASA NTRS1979

Solar wind latitudinal variations deduced from Mariner 10 interplanetary H /1216 A/ observations

The Mariner 10 H (1216-A) interplanetary observations are examined by using models that consider anisotropies in the solar fluxes. It is verified that the dominant contribution to asymmetric structure in the Mariner 10 H (1216-A) data is a latitudinal variation of the solar-wind flux and of the solar wind velocity, leading to a hydrogen atom lifetime that is latitude dependent. The average lifetime at 1 AU is found to increase from the solar equator to the solar poles by about 25%. This allows interstellar hydrogen to penetrate closer to the solar poles than to the equator. A general analytic model is constructed for evaluating the neutral hydrogen density distribution in interplanetary space. This model takes into account the latitude-dependent ionization rate. When this model is applied to the Mariner 10 H (1216-A) data, it is shown to be capable of matching the observations with a statistical accuracy of 5%. The effect of this latitudinal variation on H (1216-A) sky background maps is to produce a latitudinal shift in the maximum toward the north ecliptic pole.

Witt, N.↗

NASA NTRS1979

Statistical and computational uncertainties in atmospheric profiles from radio occultation - Mariner 10 at Venus

Statistical error in Mariner 10 occultation profiles is traced from initial observations to reduced temperature, pressure, and absorption profiles. It is shown that for the Mariner 10 profile with a height of resolution of 0.1 km, statistical measurement errors lead to uncertainties in temperature that are less than 2 K at all altitudes considered and are typically less than 0.5 K. Attention is also given to uncertainties in pressure and atmospheric absorption. In addition it is found that there is also a systematic error in the reduction of two-way data that arises from the parallax between the uplink and downlink ray paths. Finally, it is concluded that if the systematic error can be reduced to the level of the statistical noise in Mariner 10, then long term studies of thick atmospheres by occultation techniques will be feasible in the future at good levels of accuracy.

Lipa, B.↗

NASA NTRS1979

The Lyman-alpha observations of comet Kohoutek from Mariner 10

The paper presents the Lyman-alpha data from postperihelion observations of comet Kohoutek made with Mariner 10 UV spectrometer during the 1974 January 11-24 period when the comet distance from the sun varied from 0.521 AU to 0.860 AU. These data are analyzed to determine the hydrogen production rates. It is noted that observations against the low interplanetary background allowed a measurement of the hydrogen corona over 30 million km (or 15 minutes) as seen from the Mariner 10 spacecraft. The bulk of the observations can be fitted with a non-steady-state model assuming two velocity components (20 km/sec and 8 km/sec) of equal proportions. A 70% increase in the hydrogen production rate is found within 2 days from January 17 to 19 while the comet receded from the sun. Finally, it is noted that the postperihelion production rates from the Mariner 10 observations are comparable to the preperihelion production rates reported previously.

Kumar, S.↗

NASA NTRS1979

Characterization of three types of silicon solar cells for SEPS deep space missions. Volume 1: Current-voltage characteristics of OCLI BSF/BSR 10 ohm-cm, and BSR 2 ohm-cm cells as a function of temperature and intensity

Three types of high performance silicon solar cells, BSF/BSR 10 ohm-cm, BSR 10 ohm-cm, and BSR 2 ohm-cm, were evaluated for their low temperature and low intensity performance. Sixteen cells of each type were subjected to ten temperatures and nine intensities. The BSF/BSR 10 ohm-cm cells provided the best performance at 1 solar constant and +25 C with an efficiency of 14.1% while the BSR 2 ohm-cm cells had the highest low temperature and low intensity performance with an efficiency of 22.2% at 0.04 solar constant and -170 C and the most consistent cell-to-cell characteristics.

Whitaker, A. F.↗