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NASA NTRS1974

Pioneer 10

On Dec. 4, 1973, after 21 months in flight, Pioneer 10 passed by Jupiter at a distance within 130,000 km of its cloud tops. During the month before and after, instrumentation on the spacecraft made a number of scientific measurements of the Jupiter environment, thus completing one of three scientific objectives of the mission. Previously, Pioneer 10 had explored the asteroid belt and had completed the second scientific objective by determining that the belt did not present a hazard to spacecraft passing through it. The third objective, the exploration of interplanetary phenomena, started with the launch of Pioneer 10 and will not be completed until 1977 when the spacecraft nears the orbit of Uranus and the signal from the spacecraft becomes too weak to be heard at ground receivers.

Hall, C. F.↗

NASA NTRS1974

Preliminary results on the atmospheres of Io and Jupiter from the Pioneer 10 S-band occultation experiment

The preliminary analysis of data from the Pioneer 10 S-band radio occultation experiment has revealed the presence of an ionosphere on the Jovian satellite Io having an electron density peak of about 60,000 electrons per cubic centimeter at an altitude of approximately 60 to 140 kilometers. This suggests the presence of an atmosphere having a surface number density of about 10 billion to one trillion per cubic centimeter, corresponding to an atmospheric surface pressure of between .1 and 10 nanobar, at or below the detection threshold of the Beta Scorpii stellar occultation. A measurement of the atmosphere of Jupiter was obtained down to the level of about 80 millibars, indicating a large temperature increase at about the 20 millibar level, which cannot be explained by the absorption of solar radiation by methane alone and can possibly be due to absorption by particulate matter.

Kliore, A.↗

NASA NTRS1974

Gravity results from Pioneer 10 Doppler data

Two-way Doppler data received from Pioneer 10 during its encounter with Jupiter have been analyzed, and preliminary results have been obtained on the mass and the gravity field of Jupiter and on the masses of the four Galilean satellites. The ratios of the masses of the satellites to the mass of Jupiter are approximately 0.00004696 for Io, 0.00002565 for Europa, 0.00007845 for Ganymede, and 0.00005603 for Callisto (all error estimates presented in this paper are standard errors; those for Pioneer 10 represent our evaluation of the real errors as distinguished from formal errors). The ratio of the mass of the sun to the mass of the Jupiter system is about 1047.342, which is in good agreement with recent determinations from the motions of asteroids. The second- and fourth-degree zonal harmonic coefficients in the gravity field of Jupiter are 0.014720 and -0.00065, respectively, based on an equatorial planetary radius of 71,400 km, and the derived dynamical oblateness is 0.0647 at the same radius. The Pioneer 10 data are consistent with the assumption that Jupiter is in hydrostatic equilibrium at all levels.

Anderson, J. D.↗

NASA NTRS1974

Optical measurement of interplanetary particulates from Pioneer 10

The spatial concentration and size distribution for particulates measured in situ by the asteroid/meteoroid detector on Pioneer 10 between 1.0 and 3.5 AU are presented. The size distribution includes particles of radii from about 35 microns to 10 cm. Extrapolation from the smallest particle sizes measured shows good agreement with the results of the particle penetration detector carried on the same spacecraft. Within the uncertainties of this experiment, a single size distribution seems appropriate for all but the smallest particles measured. There is evidence for the existence of a planetary sweeping effect in the vicinity of the Mars orbit. As calculated from the particle spatial distribution, the zodiacal light brightness is found to vary approximately as the inverse square of solar distance out to about 2.25 AU and then decrease more rapidly. The absolute value of the zodiacal light brightness as calculated from the particle spatial concentration is found to be too high by a factor of 10.

Soberman, R. K.↗

NASA NTRS1975

Procedure for locating 10 km UTM grid on Alabama County general highway maps

Each county highway map has a geographic grid of degrees and tens of minutes in both longitude and latitude in the margins and within the map as intersection crosses. These will be used to locate the universal transverse mercator (UTM) grid at 10 km intervals. Since the maps used may have stretched or shrunk in height and/or width, interpolation should be done between the 10 min intersections when possible. A table of UTM coordinates of 10 min intersections is required and included. In Alabama, all eastings are referred to a false easting of 500,000 m at 87 deg W longitude (central meridian, CM).

Paludan, C. T. N.↗

NASA NTRS1975

The atmosphere of Io from Pioneer 10 radio occultation measurements

The occultation of the Pioneer 10 spacecraft by Io (JI) provided an opportunity to obtain two S-band radio occultation measurements of its atmosphere. The day-side entry measurements revealed an ionosphere having a peak density of about 60,000 el/cu cm at an altitude of about 100 km. The topside scale height indicates a plasma temperature of about 406 K if it is composed of Na(+) and 495 K if N2(+) is principal ion. A thinner and less dense ionosphere was observed on the exit (night side), having a peak density of 9,000 el/cu cm at an altitude of 50 km. The topside plasma temperature is 160 K for N2(-) and 131 K for Na(+). If the ionosphere is produced by photoionization in a manner analogous to the ionospheres of the terrestrial planets, the density of neutral particles at the surface of Io is less than 10 to 1 trillion per cu cm, corresponding to a surface pressure of less than 10 to 1 nanobars.

Kliore, A. J.↗

NASA NTRS1975

Upper limits to the quiet-time solar neutron flux from 10 to 100 MeV

The UCR large area solid-angle double scatter neutron telescope was flown to search for solar neutrons on 3 balloon flights on September 26, 1971, May 14, 1972 and September 19, 1972. The first two flights were launched from Palestine, Texas and the third from Cape Girardeau, Missouri. The float altitude on each flight was at about 5 g/sq cm residual atmosphere. Neutrons from 10 to 100 MeV were measured. No solar flares occurred during the flights. Upper limits to the quiet time solar neutron fluxes at the 95% confidence level are .00028, .00046, .00096 and .00090 neutrons/sq cm-sec in the energy intervals of 10-30, 30-50, 50-100 and 10-100 MeV, respectively.

Moon, S.↗

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.↗