John E Bergesen

US Patent:

58624953, Jan 19, 1999

Filed:

Sep 18, 1996

Appl. No.:

8/714329

Inventors:

Hunt W. Small - Saratoga CA
John E. Bergesen - San Bruno CA
Brian J. Howley - Mountain View CA

Assignee:

Lockheed Martin Corp. - Sunnyvale CA

International Classification:

G06F 770

US Classification:

701 13

Abstract:

Real time correction to ground generated satellite ephemeris implements a reference trajectory management module (334), an error estimation module (336), an parameter calculation module (338) and a position information management module (340). The reference trajectory management module (334) accesses reference trajectory data such as ground generated ephemeris data which is uplinked to a spacecraft through a communications unit (312). The position information management module (340) accesses and interprets position information such as Global Positioning System (GPS) measurement data to provide measured spacecraft positions. The parameter calculation module (338) calculates spacecraft position and velocity from the reference trajectory data. The error estimation module (336) compares the measured and calculated positions to provide a position difference, smoothes the position difference to filter anomalous data, and provides a correction term for the determination of corrected spacecraft orbital parameters such as position and velocity. The time rate of change of the correction term may be used to provide additional correction to the orbital parameters.