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Schubert, G.

Publications and source records attributed to Schubert, G..

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Lunar electromagnetic scattering. 1: Propagation parallel to the diamagnetic cavity axis

An analytic theory is developed for the time dependent magnetic fields inside the Moon and the diamagnetic cavity when the interplanetary electromagnetic field fluctuation propagates parallel to the cavity axis. The Moon model has an electrical conductivity which is an arbitrary function of radius. The lunar cavity is modelled by a nonconducting cylinder extending infinitely far downstream. For frequencies less than about 50 Hz, the cavity is a cylindrical waveguide below cutoff. Thus, cavity field perturbations due to the Moon do not propagate down the cavity, but are instead attenuated with distance downstream from the Moon.

Schwartz, K.↗
NASA NTRS1972

Nightside electromagnetic response of the moon

The electromagnetic response of the Moon to excitation by the time dependent fluctuations of the interplanetary magnetic field is given for the dark or antisolar hemisphere of the Moon. Six hours of time series data from the Explorer 35 magnetometer and the lunar surface magnetometer on Apollo 12 are used to obtain the Fourier spectral amplitudes of the surface and interplanetary fields from which transfer functions are calculated for the east-west, north-south, and vertical directions at the Apollo site. A critical discussion of lunar conductivity profiles derived from night side radial magnetic field data and vacuum scattering theory is presented. Limitations are shown that there is no evidence for a lunar core as conducting as 0.01 mhos/m.

Schubert, G.↗
NASA NTRS1972

An integrated study of earth resources in the state of California based on ERTS-1 and supporting aircraft data

There are no author-identified significant results in this report. Results of an integrated study of earth resources in the state of California using ERTS-1 and supporting aircraft data are presented. Areas of investigation cover (1) regional agricultural surveys; (2) solving water resource management problems; (3) resource management in Northern California using ERTS-1 data; (4) analysis of river meanders; (5) assessment and monitoring change in west side of the San Joaquin Valley and central coastal zone of state; (6) assessment and monitoring of changes in Southern California environment; (7) digital handling and processing of ERTS-1 data; (8) use of ERTS-1 data in educational and applied research programs of the Agricultural Extension Service; and (9) identification, classification, and mapping of salt affected soils.

Colwell, R. N.↗
NASA NTRS1972

The Induced Magnetic Field of the Moon: Conductivity Profiles and Inferred Temperature

Electromagnetic induction in the moon driven by fluctuations of the interplanetary magnetic field is used to determine the lunar bulk electrical conductivity. The present data clearly show the north-south and east-west transfer function difference as well as high frequency rollover. The difference is shown to be compatible over the mid-frequency range with a noise source associated with the compression of the local remanent field by solar wind dynamic pressure fluctuations. Models for two, three, and four layer; current layer, double current layer, and core plus current layer moons are generated by inversion of the data using a theory which incorporates higher order multipoles. Core radii conductivities generally are in the range 1200 to 1300 km and 0.001 to 0.003 mhos/m; and for the conducting shell 1500 to 1700 km with 0.0001 to 0.0007 mhos/m with an outer layer taken as nonconducting. Core temperature based on available olivine data is 700 to 1000 C.

Sonett, C. P.↗
NASA NTRS1972

The particles and fields subsatellite magnetometer experiment

A preliminary analysis of magnetometer data from Apollo 15 subsatellite is concluded. Remanent magnetization is a characteristic property of the moon, and the distribution is such that a complex pattern is produced. A mapping of the distribution is feasible with the present experiment. Lunar induction fields produced by transients in interplanetary magnetic field are detectable at satellite orbit. Magnetometer data will provide estimates of the latitude and longitude dependences of interior conductivity. The plasma void extends to some altitude below the satellite orbit and probably the lunar surface. Solar wind near the limbs is usually strongly disturbed.

Coleman, P. J., Jr.↗
NASA NTRS1972

High-frequency electromagnetic response of the moon.

It is shown that the contribution of higher harmonics to the lunar transfer functions for the tangential components of the surface magnetic field is significant at frequencies greater than 0.01 Hz. The inclusion of the higher harmonics shows that there are two distinct transfer functions corresponding to the components of the tangential surface magnetic field perpendicular and parallel to the direction of the wave vector of the external disturbance forcing the lunar induction. The dependences of these transfer functions on frequency and location are determined. The effects of the higher harmonics can (1) account for a hitherto unexplained feature in the Apollo 12 and Explorer 35 transfer functions, namely the rolloff at high frequencies, and (2) offer a possible explanation for the frequency dependence of the difference between the transfer functions for the two orthogonal components of the surface magnetic field.

Schubert, G.↗
NASA NTRS1972

Lunar surface magnetometer experiment

The Apollo 16 lunar surface magnetometer (LSM) activation completed the network installation of magnetic observatories on the lunar surface and initiated simultaneous measurements of the global response of the moon to large-scale solar and terrestrial magnetic fields. Fossil remanent magnetic fields have been measured at nine locations on the lunar surface, including the Apollo 16 LSM site in the Descartes highlands area. This fossil record indicates the possible existence of an ancient lunar dynamo or a solar or terrestrial field much stronger than exists at present. The experimental technique and operation of the LSM are described and the results obtained are discussed.

Dyal, P.↗
NASA NTRS1972

The particles and fields subsatellite magnetometer experiment

It is reported that the objectives of the particles and fields subsatellite (PFS) magnetometer experiment are to calculate the interior electrical conductivity of the moon, to survey the remanent magnetization of the lunar surface, and to study the interaction of the moon with its plasma environment. The magnetometers also support the PFS particle experiment by providing onboard magnetic sectoring and a posteriori pitch angle data and plasma diagnostics.

Coleman, P. J., Jr.↗
NASA NTRS1972

Analysis and interpretation of lunar laser altimetry.

About 4.5 revolutions of laser altimetry were obtained by Apollo 15. This altimetry indicates a 2-km displacement of the center of mass from the center of figure toward the earthside. The terrae are quite rough, with frequent changes of 1 km or more in successive altitudes at about 33-km intervals. The mean altitude of terrae above maria is about 3 km with respect to the center of mass, indicating a thickness of about 24 km for a high-alumina crust. The maria are extremely level, with elevations varying not more than plus or minus 150 m about the mean over some stretches of 200 to 600 km. However, different maria have considerably different mean elevations. The largest unanticipated feature found is a 1400 km wide depression centered at about 180 deg longitude, and 2 km deep with respect to a 1737-km sphere (about 6 km deep with respect to the surrounding terrae). This basin has the appearance of typical terrae, although there are indications of a ring structure of about 600-km radius in the Orbiter photography. Altitudes across circum-Orientale features suggest that Mare Orientale is also a deep basin. The data appear to corroborate a model of early large-scale differentiation of a crust, followed a considerable time later by short intense episodes of mare filling with low viscosity lavas.

Kaula, W. M.↗
NASA NTRS1972

The induced magnetic field of the moon - Conductivity profiles and inferred temperature.

Electromagnetic induction in the moon driven by fluctuations of the interplanetary magnetic field is used to determine the lunar bulk electrical conductivity. The earlier data are now augmented by an order of magnitude. The present data clearly show the north-south and east-west transfer function difference as well as the high-frequency rollover suggested earlier. The difference is shown to be compatible over the midfrequency range (0.001 to 0.01 Hz) with a noise source associated with the compression of the local remanent field by solar wind dynamic pressure fluctuations. The rollover of the transfer functions is shown to result from higher order magnetic multipole radiation; electric multipoles appear supressed, although a vestigial TM interaction may still be present. Models for two, three, and four layer; current layer, double current layer, and core plus current layer moons are generated by inversion of the data, using a theory that incorporates higher-order multipoles.

Sonett, C. P.↗
NASA NTRS1972

Preliminary mapping of the lunar magnetic field

Magnetic field measurements made with the Apollo 15 subsatellite established the existence of remanent magnetization over much of the Moon's surface. The major features of the structure of the measured remanent field are apparently associated with large craters, the most apparent detected to date being that in the vicinity of the Van de Graaff crater. A preliminary contour map of relative magnetic intensity was produced for a limited region of the Moon. A high resolution plot of the Van de Graaff region was constructed from vector data in an attempt to locate the source of the largest feature observed.

Coleman, P. J., Jr.↗
NASA NTRS1971

South polar and equatorial differences in central peaked Martian craters.

Description of the results of a preliminary study of the distribution of central peaked Martian craters based on photographs taken by Mariner 6 and 7. The study provides information about the origin of these craters and about the geological processes occurring on the surface of Mars. It is pointed out that central peaks in Martian craters in the south polar region occur more frequently than their equatorial counterparts and the peak frequency statistics and crater morphologies imply that preferential peak production has taken place.

Cordell, B. M.↗
NASA NTRS1971

Thin highly conducting layer in the moon - Consistent interpretation of dayside and nightside electromagnetic responses.

The vacuum transient response of the moon to a time-varying spatially uniform magnetic field is determined for a lunar electrical conductivity model that was based on the harmonic analysis of Apollo 12 and Explorer 35 dayside magnetometer data. The transient response of the model is found to provide a plausible explanation of the behavior of the local vertical-surface magnetic field for an Apollo 12 magnetometer darkside transient event. A model containing a conducting core and a highly conducting thin subsurface layer is presented, and its transient behavior is discussed.

Schubert, G.↗
NASA NTRS1971

High frequency electromagnetic response of the moon

It is shown that the contribution of higher harmonics to the lunar transfer functions for the tangential components of the surface magnetic field is significant at frequencies greater than 0.01 Hz. The inclusion of the higher harmonics shows that there are two distinct transfer functions corresponding to the components of the tangential surface magnetic field perpendicular and parallel to the direction of the wave vector of the external disturbance forcing the lunar induction. The dependences of these transfer functions on frequency and location are determined. The effects of the higher harmonics can: (1) account for a hitherto unexplained feature in the Apollo 12-Explorer 35 transfer functions, namely the rolloff at high frequencies; and (2) offer a possible explanation for the frequency dependence of the difference between the transfer functions for the two orthogonal components of the surface magnetic field. The harmonic response of a simple current layer model of the moon is derived.

Schubert, G.↗
NASA NTRS1971

Lunar electrical conductivity profile

Lunar electrical conductivity profile measurements, providing mantle-core stratification near surface thermal gradient, heat flux and composition data

Colburn, D. S.↗