nd SEEs 4.2.1 4.2.2 Optical Link Photodetectors 4.2.3 Optocouplers and MSM Photodiodes 4.3 Destructive Failures from Single Proton Interactions 4.3.1 Latch-Up (and COTS) 4.3.2 Proton-Induced Single Event Burnout 4.3.3 Stuck Bits 5.0 Summary 6.0 Acknowledgments 7.0 References for General Introduction and Section IVA SECTION IVA: IONIZATION EFFECTS Paul W. Marshall and Cheryl J. Marshall 1.0 INTRODUCTION This first segment covers various ways in which proton-induced ionization can affect circuit operation. For our purpose, this includes TID effects as well as both direct and indirect single event phenomena. Before addressing the device and circuit effects, we offer a brief overview of the near-Earth proton environments and issues impacting the environment description internal to the satellite. This section also provides examples and discusses issues concerning the generation of design requirements based on the expected environment. Following the environment section, we offer a brief discussion of proton-specific concerns for TID effects. Next, the fourth section examines soft errors due to protons, again with emphasis on recent developments, and the fifth section looks at hard errors. PROTON ENVIRONMENTS FOR SATELLITES Protons occur in every imaginable orbit with variations in spectral energy composition, arrival rates, and sometimes arrival trajectories. The three sources are trapped protons in the inner Van Allen radiation belt, the proton component of solar particle events, and hydrogen nuclei from intergalactic cosmic rays. Careful discussions of the near-Earth, interplanetary, and other planet proton environment models are available in the Conference Short Course notes from 1997 [Bart-97]. The interested reader should refer to those notes and the cited literature to gain an understanding of the characteristics and shortcomings of the widely used NASA AP-8 [Sawy-76] model for trapped protons, the CREME-96 [Tylk-96] cosmic ray model, and various descriptions of solar proton probability models. These models shoul