The solutions evolved over the next two decades (see "The Methuselah Project," February/March 1987). Of considerable help was the development of a system the instrument uses to compensate for even the faintest trace of drag from the Earth’s atmosphere. The system relies on a quartz sphere (identical to one of the gyros) that is kept shielded from external accelerations in a cavity near the spacecraft’s center of mass. Because it is so well isolated, the sphere follows an ideal gravitational orbit; the spacecraft, sensing the reference sphere’s position, will continually apply thrust forces to "chase after" the sphere, and thus end up moving in a near-perfect orbit itself.
More than a dozen technologies and engineering methods have emerged from the GP-B program, as well as 44 Ph.D.’s, five engineering degrees, and 12 master’s degrees. With most of the conceptual and technical hurdles behind them and the launch of the instrument tentatively scheduled for 1998, the project team is now working on refining individual components-for example, nudging the quartz gyroscopes--already the roundest object ever made--a few ten-millionths of an inch closer to perfect sphericity, and integrating them into a working whole.