Planetary Astronomy; an Appraisal of Ground-Based Opportunities (1968) / Chapter Skim
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Dynamics of the Planetary System
Dynamics of the Planetary System
Pages 7-13
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From page 7... ...
Because the computer has become an integral part of every scientific laboratory, it may not be necessary to stress its central importance to the solution of problems in celestial mechanics: classes of problems can now be undertaken which would otherwise remain inaccessible. The significance of ground-based radar in the study of planetary motions rests on its ability to measure, with high resolution, the power-density distribution in time (delay)
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From page 8... ...
Because the systematic errors associated with radar measurements affect the results in a manner qualitatively different from those accompanying optical observations, the presence of systematic errors in both types of data can be detected more accurately through cross-checking. A few of the ramifications of the new techniques in celestial mechanics which appear to be of exceptional interest have been selected for more detailed discussion.
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From page 9... ...
The first category comprises not only the classical attempts to measure the apparent bending of starlight that passes near the solar limb but also the more recent proposal to measure the apparent retardation in propagation velocity along a similar path, made possible by the use of radar time-of-flight data. In the second category are included the additional secular advances of planetary perihelia and periodic orbital perturbations.
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From page 10... ...
With the accuracy in delay measurement improved to the level of a microsecond, it should be possible after several years of radar observation to achieve a sensitivity of the order of 10"11 per year in this variation. Many of the tests discussed in this section conceivably could be performed by an artificial solar satellite, suitably instrumented with radio and perhaps optical transponders.
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From page 11... ...
Chemical and physical characteristics of most meteorites suggest that they have undergone processing within bodies of asteroidal size, and the few reliable atmospheric trajectories available are not inconsistent with asteroidal origin of meteorites. The marked variation among meteorites raises questions of whether asteroids have comparable differences and variations in composition and whether
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From page 12... ...
Observations of even short-period comets have extended over as much as half of the orbit in only two cases. The complex gravitational interactions of major planets with each other and with comets will require careful evaluation as improved determinations of distances, planetary masses, and orbital elements are obtained through refinement of classical techniques and from radar observations.
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From page 13... ...
Special efforts would also be usefully directed toward the discovery and observation of asteroids crossing the Earth's orbit.
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