Gravitational Field Models for the Earth (GEM 1 & 2)

Lerch, F.J.; Wagner, C.A.; Smith, D.E.; Sandson, M.L.; Brownd, J.E.; Richardson, J.A.

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Gravitational Field Models for the Earth (GEM 1 & 2)

Lerch, F., Wagner, C., Smith, D., Sandson, M., Brownd, J., Richardson, J. (1972): Gravitational Field Models for the Earth (GEM 1 & 2), (NASA Technical Reports), Greenbelt, Md. : Center, GSFC Goddard Space Flight, 35 p.

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Item Permalink: https://gfzpublic.gfz-potsdam.de/pubman/item/item_1834038 Version Permalink: https://gfzpublic.gfz-potsdam.de/pubman/item/item_1834038_3

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Lerch, F.J.^{1, 2}, Author
Wagner, C.A.^{1, 2}, Author
Smith, D.E.^{1, 2}, Author
Sandson, M.L.^{1, 2}, Author
Brownd, J.E.^{1, 2}, Author
Richardson, J.A.^{1, 2}, Author

Affiliations:
1Publikationen aller ICGEM-unterstützten Projekte, Deutsches GeoForschungsZentrum, , , ou_1684888
2External Organizations, ou_persistent22

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Free keywords: EARTH GRAVITATION GEOMAGNETISM GRAVITATIONAL FIELDS GEOPOTENTIAL GRAVIMETRY OPTICAL TRACKING SATELLITE TRACKING

Abstract: Two models of the earth's gravitational field have been computed at Goddard Space Flight Center. The first, Goddard Earth Model 1 (GEM 1), has been derived from satellite tracking data. The second, Goddard Earth Model 2 (GEM 2), has been derived from a combination of satellite tracking and surface gravimetric data. The geopotential models are represented in spherical harmonics complete to degree and order 16 for the combined solution and complete to degree and order 12 for the satellite solution. Both solutions include zonal terms to degree 21 and related satellite resonant coefficients to degree 22. The satellite data consisted primarily of optical data processed on 300 weekly orbital arcs for 25 close earth satellites. Surface gravity data were employed in the form of 5 deg x 5 deg mean free-air gravity anomalies providing about 70% world coverage. Station locations were obtained for 46 tracking sites by combining electronic, laser, and additional optical tracking data with the above satellite data. Analysis of the radial positions of these stations and a value of mean gravity on the geoid indicated a mean equatorial radius for the earth of about 6378145 meters. Results of geopotential tests on satellite data not used in the solution show that better agreement was obtained with the GEM 1 and GEM 2 models than with the 1969 Smithsonian Standard Earth 2 model.

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Dates: Finally published : 1972

Publication Status: Finally published

Pages: 35

Publishing info: Greenbelt, Md. : Center, GSFC Goddard Space Flight

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Identifiers: Other: NASA-TM-X-65970, X-553-72-146
URI: http://hdl.handle.net/2060/19720021773

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Title: NASA Technical Reports

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Pages: - Volume / Issue: - Sequence Number: - Start / End Page: - Identifier: Report Nr.: NASA-TM-X-65970, X-553-72-146