Dynamic satellite geodesy

Since the last quadrennial report [Gaposchkin, 1971], dynamic satellite geodesy has been continually refined with several new and independent solutions for the gravity field [Yionoulis et al., 1972; Gaposchkin, 1973a, 1974; Lerch et al., 1972a, b, 1974; Lerch and Wagner, 1972; Rapp, 1971a, 1973a, b, 1974a; Koch, 1972, 1974; Koch and Witte, 1971; Koch and Morrison, 1970] and station coordinates [Anderle, 1974a; Gaposchkin, 1973a, 1974; Lerch et al., 1972a, b, 1974; Lerch and Wagner, 1972; Marsh et al., 1971, 1972, 1973a, b; Koch, 1972, 1974; Koch and Witte, 1971; Koch and Morrison, 1970]. The new results have led to a consolidation of the discipline and have provided general agreement for these geodetic parameters. In addition, a milestone was achieved with the completion of The National Geodetic Satellite Program (NGSP), sponsored by the National Aeronautics and Space Administration (NASA). Many of the above‐mentioned results, the product of that program, are documented by the National Aeronautics and Space Administration [1975]. The NGSP was based on what have become classical satellite methods. In addition, some new and exciting observing techniques, now coming into use under the sponsorship of the NASA Earth and Ocean Physics Applications Program (Eopap), will be complementary to the classical satellite and terrestrial methods. These techniques include the use of satellite‐to‐sea‐surface radar altimetry and satellite‐to‐satellite tracking. An important technological achievement was accomplished with the successful launch and operation of the surface force compensated satellite Triad [Black, 1973]; such force compensation allows the corrupting effects of nongravitational forces to be eliminated from future geodetic analyses. A similar objective is sought with the imminent launch of Lageos, which will be used for the dynamical determination, to centimeter accuracy, of site locations, polar motion, and crustal displacement.