January 2011 Meeting Summary

Col Gaylord Green spoke to the Southern California Section about Gravity Probe B on Jan. 27, 2011, 2010 at NavCom Technology. There were more than 40 in attendance. A brief bio and abstract of the talk follows, and the slides used during the meeting are attached.

Capsule Biography of Col Gaylord Green (USAF Ret):
Col Green is the President of NavAstro, a company engaged in space experiments with Stanford University and in GPS III developments. Col. Green is a Past President of the ION and a winner of the Hays award. He was also a Director of the GPS Joint Program Office and earlier was the Space Segment Chief, as well as having done much of the systems engineering in the beginning. He directed the Gravity Probe B program for Stanford University from 1989 until 2007. He continues to be a member of the Independent Review Team for GPS and a member of the Independent Assessment Team for the GPS Wing. He is a graduate of the Air Force Academy and has an M.S. degree in Aeronautics and Astronautics from Stanford. Col. Green holds many awards and honors for his work and leadership in GPS and ballistic missile technology.

Abstract of Col. Green’s Talk:
Slides: Gravity Probe B
The Gravity Probe B (GP-B) program tested two distinct effects of General Relativity: The Geodetic Effect and Frame-Dragging. General relativity holds that a massive body like the Earth warps the space-time around it, creating the geodetic effect. Frame-dragging is the predicted effect that occurs when a rotating body spins on its axis, “dragging” the space-time around it. GP-B tested the two predicted effects of general relativity: the geodetic effect and frame-dragging.

The experiment necessary to determine this must measure minute changes in the spin direction of a set of extremely precise gyroscopes placed in a polar orbit 400 miles above the Earth. The GP-B experiment required one of the most sophisticated spacecraft designs ever utilized for a NASA mission. For many less complex science missions, the spacecraft bus (i.e., the spacecraft without its instruments or electronics) serves essentially as a vehicle to transport and house the instruments. With GP-B, though, the experiments required such a degree of exactitude that the spacecraft itself played an active part in the functioning of the instruments.

GP-B employed the world’s most precise gyroscopes, spinning in a vacuum that insulated them from the effects of any external forces. The gyro’s rotors were the most spherical objects ever produced, rotating at high speed in tight casings that they could not touch. The maintenance of a perfectly drag-free environment required the spacecraft to use micro-thrusters to make constant minute adjustments in its position in order to keep the gyros perfectly in place.

GP-B’s management structure was unique among NASA programs and projects. In 1985 NASA had designated Stanford University as the prime contractor for the spacecraft, giving Stanford full program management responsibility. Lockheed Martin was awarded the subcontract to supply the spacecraft as well as some components of the payload, and it reported directly to Stanford, not NASA. This arrangement, which was dubbed “The Management Experiment” by NASA Administrator James M. Beggs at the time, remained in place until 1998, when NASA decided to take a more hands-on approach.

Col Green will cover both the complex engineering and the scientific aspects of this unprecedented program which has contributed so much to our knowledge of basic physics and cosmology.