The Evolution of IMP Spacecraft Mosfet Data Systems

Since 1964 the Interplanetary Monitoring Platform spacecraft data systems have used MOSFET devices. Many millions of device hours have been accumulated from IMPs D,E,F and G in orbit without any "proven failures" (two possible non-catastrophic failures may have occurred on MOSFET chips in IMP-D well after a year in orbit). We are now using the fourth generation of MOSFET blocks in IMPs H&J where there are approximately 1000 devices on a single chip. Historically, the development of MOSFET blocks for the IMP program has progressed through four phases. The PHASE I blocks contained about 10 devices/chip, PHASE II about 50, PHASE III about 200 and presently the PHASE IV blocks contain about 1000 devices/chip. The PHASE IV data system now under fabrication uses approximately one-half million devices. This two orders of magnitude increase in the number of devices per chip, while vastly increasing the capability of the data system, has also revised the thinking used in system design and has revised the reliability approach used.