Thomas J Tanner

US Patent:

6076774, Jun 20, 2000

Filed:

Aug 12, 1998

Appl. No.:

9/132343

Inventors:

Piyush R. Shah - Germantown MD
Thomas M. Tanner - Aurora CO
Richard A. Noyola - Torrance CA

Assignee:

Hughes Electronics Corporation - El Segundo CA

International Classification:

B64G 124

US Classification:

244164

Abstract:

A system and method for acquiring the Earth by a three-axis stabilized spacecraft in the presence of a significantly time-varying Sun-Earth angle including obtaining an Earth cone described by rotating the nadir vector about the Sun vector, slewing the spacecraft about an axis until the Earth sensor boresight touches an edge of the Earth cone, updating the Earth cone due to the changing Sun-Earth separation angle, performing a spiral coning maneuver about the updated Earth cone until the Earth sensor detects the Earth, and locking onto the Earth so as to hold the Earth sensor boresight coincident with the nadir vector. Additionally, the spacecraft may be rotated about the nadir vector so as to bring the spacecraft into a desired final attitude.