The Computers On-board the Spacecraft

GP-B has several computers on-board the spacecraft. The main flight computer and its twin backup are called the CCCA (Command & Control Computer Assembly). These computers were assembled for GP-B by the Southwest Research Institute. They use approximately 10-year old IBM RS6000 Central Processing Units (CPUs), with 4 MB of radiation-hardened RAM memory. These computers, along with ruggedized power supplies are encased in sturdy aluminum boxes, with sides up to 1/4” thick.In addition to the A-side (main) and B-Side (backup) flight computers, the GP-B spacecraft has two other special-purpose computers—one for the Gyro Suspension System (GSS) and one for the SQUID Readout Electronics (SRE). Each of these specialized computers contains 3 MB of radiation-hardened RAM memory and custom circuit boards designed and built here at Stanford University. Because of the custom circuit boards, these computers are housed in special aluminum boxes that were also built at Stanford.