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GPS orbit determination at the National Geodetic SurveyThe National Geodetic Survey (NGS) independently generates precise ephemerides for all available Global Positioning System (GPS) satellites. Beginning in 1991, these ephemerides were produced from double-differenced phase observations solely from the Cooperative International GPS Network (CIGNET) tracking sites. The double-difference technique combines simultaneous observations of two satellites from two ground stations effectively eliminating satellite and ground receiver clock errors, and the Selective Availability (S/A) signal degradation currently in effect. CIGNET is a global GPS tracking network whose primary purpose is to provide data for orbit production. The CIGNET data are collected daily at NGS and are available to the public. Each ephemeris covers a single week and is available within one month after the data were taken. Verification is by baseline repeatability and direct comparison with other ephemerides. Typically, an ephemeris is accurate at a few parts in 10(exp 7). This corresponds to a 10 meter error in the reported satellite positions. NGS is actively investigating methods to improve the accuracy of its orbits, the ultimate goal being one part in 10(exp 8) or better. The ephemerides are generally available to the public through the Coast Guard GPS Information Center or directly from NGS through the Geodetic Information Service. An overview of the techniques and software used in orbit generation will be given, the current status of CIGNET will be described, and a summary of the ephemeris verification results will be presented.
Document ID
19920024110
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
M. S. Schenewerk
(National Oceanic and Atmospheric Administration Rockville, MD, United States)
Date Acquired
September 6, 2013
Publication Date
December 3, 1991
Publication Information
Publication: 23rd Annual Time and Time Precise Interval (PTTI) Applications and Planning Meeting
Publisher: National Aeronautics and Space Administration
Volume: 3159
Issue Publication Date: January 1, 1992
Subject Category
Aircraft Communications And Navigation
Meeting Information
Meeting: 23rd Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting
Location: Pasadena, CA
Country: US
Start Date: December 3, 1991
End Date: December 5, 1991
Sponsors: United States Naval Observatory, Goddard Space Flight Center, Jet Propulsion Lab
Accession Number
92N33354
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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