Microprocessor program storage for missions with high radiation exposure

Microprocessors have become an indispensable part of modern instruments for space research missions. A suitable selection of microprocessors and peripheral components must take into consideration also the operational performance of the devices when exposed to radiation, and their capability to withstand radiation. One of the devices to be considered is the memory unit employed for storing the program. Conditions of a particularly high exposure to radiation will exist during the Galileo and ISPM missions. While passing through the magnetic field of Jupiter, the equipment of the spacecraft will be exposed to a flux of high-energy electrons and protons. Performance under the expected conditions, availability, and cost are compared for several types of memory. It is found that the employment of bipolar PROMs has distinct advantages when compared to a use of CMOS ROMs or RAMs.