le orbits in each of these categories and illustrates proton and other radiation characteristics of those orbits for the purpose of ionizing (but not displacement) effects space-borne computers. Be warned though, that these are only examples and there is no justification to generalize from those orbits even to other orbits within the same category. For the designer, detailed understandings of the environment models are fortunately not usually necessary. Instead, the proton and other radiation related requirements are either supplied by the procuring organization or generated "in house" by resident radiation environment experts. Several years ago, it was not uncommon to see radiation design specifications expressed in terms of total ionizing dose (or depth-dose curves) supplemented with either Linear Energy Transfer (LET) spectra or guidance with respect to LET threshold for single event induced hard errors and upset rates from cosmic rays. Proton contributions to the depth-dose may have been identified, but often there was no breakout of the expected proton energy spectra and fluxes. In many cases, it was assumed that components that could be upset by protons would be screened out by the requirement for a high threshold LET for cosmic ray effects. With today's emphasis on high performance systems and the component selections now available, all that has changed. Now a more reasonable assumption would be that proton effects are expected, and part of the designer's task is to manage the associated risk. Increasingly, it is the responsibility of the design team to assess radiation-related risk, and proton effects are often an important part of this equation. There is still quite a variation in the level of detail called out in the proton environment description provided to the design effort. It usually contains some, but rarely all, of the following elements: trapped proton total ionizing dose contribution to a depth-dose relation trapped proton energy spectra behind typical shield thickness peak trapped proton flux 