The Microelectronics Test Package (MEP) flown on board the Combined Re
lease and Radiation Effects Satellite (CRRES) contained over 60 device
types and approximately 400 total devices which were tested for both
single event upset (SEU) and total dose (parametric degradation and an
nealing). A description of the experiment, the method of testing devic
es, and the structure of data acquisition are presented. Sample flight
data are shown. These included SEUs from a GaAs 1 K RAM during the Ma
rch 1991 solar flare, and a comparison between passive shielding and a
specially designed spot shielding package.