 not considered to be a significant problem, though scaling trends suggest that this may soon change. Proton-induced stuck bits may be either temporary or permanent as reported in [Sore-95]. Figure 21, from the CRUX experiment, indicates that stuck bits have occurred in all device types included in the experiment. Though they have been correlated with solar particle events, [Bart-98] points out that most events have been outside of the SAA and therefore are more likely due to heavy ions. From a test perspective, it is common to see stuck bits during proton SEE testing as the TID limit of the technology is approached. That, along with increased leakage currents, is an indication of the need to resume the test with a fresh device. IV-41 SEBs As Function of Voltage Drain-to-Source For L<3 (August 11, 1994 to May 17, 1996) Results For 200 Volt Boards Voltage Drain-to-Source (Volts) Figure 20. The results of the power MOSFET single event burnout experiment flying on CRUX confirm that protons can lead to device failure and showed that the proton rates can exceed heavy ion induced SEB rates [Bart-98]. Stuck Bit Errors on CRUX SRAMs MICRON 1M EDI 1M HITACHI/ELMO 1M MICR ON 256K ED 256K IDT 256K L = 3 Solar Event Number of Days from Launch Figure 21. Stuck bits have occurred in all the modern memory devices flying on the CRUX experiment [Bart-98]. The chart indicates that some (for L <3) are probably due to protons, but most are thought to be heavy ion related. IV-42 5.0 SUMMARY Satellite microelectronic and photonic devices subjected to the ionizing effects of protons may exhibit responses either from total ionizing dose or from single event phenomena. Heavily shielded devices will likely receive dose primarily from protons in orbits encountering the inner radiation belts. For total ionizing dose, we have reviewed the literature comparing the equivalence of proton dose versus other sources of dose deposition found in either the space environment or in laboratory test facilities. We conclude that Co-60 and electron dose s