Closed loop navigation and guidance for Gravity Probe B orbit insertion
Abstract
The objective of the Gravity Probe B (GPB) satellite is to test two aspects of Einstein's theory of general relativity which predict that a locally inertial Newtonian coordinate frame in orbit around the earth will rotate. In a circular, 650 km polar orbit, the two effects, known as the geodetic and frame dragging precessions, are predicted to be 6.6 arc sec/yr and 42 milliarc sec/yr, respectively. These minute rotations will be measured using orbiting gyroscopes whose Newtonian drift rates are less than 0.5 milliarc sec/yr. This paper addresses the problem of guiding the GPB spacecraft from its location after initial orbit insertion to this very precise orbit. Specifically, the satellite orbit is required to be circular to within 0.001 eccentricity, polar to within 0.001 degrees inclination, and aligned with the direction of Rigel to within 0.001 degrees. Navigation data supplied by an onboard GPS receiver is used as feedback to a control algorithm designed to minimize the time to achieve the desired orbit. Translational control is provided by the proportional helium thrusters which are used for dragfree and attitude control during the remainder of the science mission.
 Publication:

ION, Satellite Division's International Technical Meeting
 Pub Date:
 1989
 Bibcode:
 1989ion..meet..193P
 Keywords:

 Control Systems Design;
 Feedback Control;
 Global Positioning System;
 Gravity Probe B;
 Space Navigation;
 Spacecraft Guidance;
 Gyroscopes;
 Polar Orbits;
 Relativity;
 Scientific Satellites;
 Space Communications, Spacecraft Communications, Command and Tracking