Hardware

Central Processing Unit

A CPU for use in space must first be MIL-STD-883 (usually Class M or S, ground based is B). This means it has met the over 100 tests that the Department of Defense has developed to insure reliable operation. These tests include: thermal, mechanical, AC electrical and DC electrical tests as well as sampling requirements for individual wafer inspections.

Also note that MOST spacecraft use many CPUs. Either for redundancy or to split tasks. Being able to separately control EACH component of a spacecraft is very important.This would be impossible if one CPU controlled them all. With each sub-system powered by its own CPU the sub-systems can be better controlled for power management and fault tolerance. (for example if one CPU dies it only would disable one instrument, not the whole spacecraft)