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Dynamic sea surface topography, gravity and improved orbit accuracies from the direct evaluation of SEASAT altimeter dataA method for the simultaneous solution of dynamic ocean topography, gravity and orbits using satellite altimeter data is described. A GEM-T1 based gravitational model called PGS-3337 that incorporates Seasat altimetry, surface gravimetry and satellite tracking data has been determined complete to degree and order 50. The altimeter data is utilized as a dynamic observation of the satellite's height above the sea surface with a degree 10 model of dynamic topography being recovered simultaneously with the orbit parameters, gravity and tidal terms in this model. PGS-3337 has a geoid uncertainty of 60 cm root-mean-square (RMS) globally, with the uncertainty over the altimeter tracked ocean being in the 25 cm range. Doppler determined orbits for Seasat, show large improvements, with the sub-30 cm radial accuracies being achieved. When altimeter data is used in orbit determination, radial orbital accuracies of 20 cm are achieved. The RMS of fit to the altimeter data directly gives 30 cm fits for Seasat when using PGS-3337 and its geoid and dynamic topography model. This performance level is two to three times better than that achieved with earlier Goddard earth models (GEM) using the dynamic topography from long-term oceanographic averages. The recovered dynamic topography reveals the global long wavelength circulation of the oceans with a resolution of 1500 km. The power in the dynamic topography recovery is now found to be closer to that of oceanographic studies than for previous satellite solutions. This is attributed primarily to the improved modeling of the geoid which has occurred. Study of the altimeter residuals reveals regions where tidal models are poor and sea state effects are major limitations.
Document ID
19890016168
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Marsh, J. G. (ST Systems Corp. Lanham, MD., United States)
Lerch, F. (ST Systems Corp. Lanham, MD., United States)
Koblinsky, C. J. (ST Systems Corp. Lanham, MD., United States)
Klosko, S. M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Robbins, J. W. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Williamson, R. G. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Patel, G. B. (ST Systems Corp. Lanham, MD., United States)
Date Acquired
September 8, 2013
Publication Date
May 1, 1989
Subject Category
Geophysics
Report/Patent Number
NAS 1.15:100735
REPT-89B0111
NASA-TM-100735
Accession Number
89N25539
Funding Number(s)
PROJECT: RTOP 161-20-25
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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