California Institute of Technology

The United States of America as Represented by the Administrator of the

Sien-Chong Wu

William I Bertiger

Stephen M Lichten

Ronald J Muellerschoen

Yoaz E Bar-Sever

Michael Heflin

Catherine Thornton

James Zumberge

Geoff Blewitt

Thomas Yunck

Kenneth Hurst

Thomas Patrick Yunck

Anthony J Mannucci

Techniques for monitoring and controlling yawing of a GPS satellite in an orbit that has an eclipsing portion out of the sunlight based on the orbital conditions of the GPS satellite. In one embodiment, a constant yaw bias is generated in the attitude control system of the GPS satellite to control the yawing of the GPS satellite when it is in the shadow of the earth.

Techniques for monitoring and controlling yaw attitude of a GPS satellite

An improved analyzing system based on GIPSY-OASIS II software package developed at the Jet Propulsion Laboratory for Global Positioning System, general satellite tracking, orbit determination and trajectory studies. New features and functions include yaw compensation, precise satellite positioning by high-rate GPS clocks, enhanced data filtering and smoothing, a new user interface for controlling orientation of a satellite and its components, and no-fiducial approach to global geodesy. The present invention allows a fully automatic operation and delivery of validated daily solutions for orbits, clocks, station locations and others with no human intervention. A 3D GPS orbit accuracy of 15 cm and the daily repeatability of the 3D global geocentric station location in better than 1 cm have been achieved.

Analyzing system for global positioning system and general satellite

The present invention provides a method and a device for providing superior differential GPS positioning data. The system includes a group of GPS receiving ground stations covering a wide area of the Earth's surface. Unlike other differential GPS systems wherein the known position of each ground station is used to geometrically compute an ephemeris for each GPS satellite, the present system utilizes real-time computation of satellite orbits based on GPS data received from fixed ground stations through a Kalman-type filter/smoother whose output adjusts a real-time orbital model. The orbital model produces and outputs orbital corrections allowing satellite ephemerides to be known with considerable greater accuracy than from the GPS system broadcasts. The modeled orbits are propagated ahead in time and differenced with actual pseudorange data to compute clock offsets at rapid intervals to compensate for SA clock dither. The orbital and clock calculations are based on dual frequency GPS data which allow computation of estimated signal delay at each ionospheric point. These delay data are used in real-time to construct and update an ionospheric shell map of total electron content which is output as part of the orbital correction data, thereby allowing single frequency users to estimate ionospheric delay with an accuracy approaching that of dual frequency users.

Robust real-time wide-area differential GPS navigation

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Torrance, CA, United States of America

Sien-Chong Wu