Gravity model improvement using Geos 3 (GEM 9 and 10)

摘要: The spaceborne altimeter missions of Geos 3 (50-cm accuracy) and the future Seasat (10-cm require precise knowledge radial position spacecraft to be most-effective. Though errors in previous gravity models have produced large uncertainties orbital 3, significant improvement has been obtained with new geopotential solutions, Goddard Earth Model (GEM) 9 10. solution for GEM was derived by combining laser data from Lageos, Starlette; S band measurements on Landsat 1; 26 other satellites used solutions. 10 is a combination containing global set surface anomalies along 9. Radial 5-day arcs reduced about 5 m 1 basis intercomparisons, station navigations, analyses employing crossover points passes altimetry. use highly accurate constrained least squares permitted larger field than satellite models, having harmonics complete 20 × selected higher-degree terms. approximately 840,000 observations, which 200,000 are ranges taken nine equipped retroreflectors. 22 terms out degree order 30 amounting total 592 coefficients. Comparisons indicate substantial over solutions; even closer agreement previously published 6 contained gravity. In particular, free air calculated Rapp (1977) excellent high-degree (13 ≤ l 22). From these an estimate made upper mantle. mass constant earth, GM, estimated as 398,600.64±0.02 km3/s2, value principally determined Lageos. speed light 299,792.5 km/s. Geocentric positions were 150 stations These coordinates, their mean sea level heights, altimetry provide radius earth ae = 6,378,139 ± m. Accuracy estimates potential coefficients verified independent sets. produce commission geoid heights 1.9 1.5 (global rms values), respectively,