ation impacting the uncertainty of the AP-8 model is discussed in section 2.4. Uncertain device response and the inability of imperfect predictive models to accurately describe performance also call for radiation design margin. These factors can be quite large, especially where the key variables governing device response are not well understood. In the portion of this Short Course segment concerning displacement damage we will illustrate this point for the cases of CCD damage and optocoupler degradation. Design margins of over two are warranted in each of these situations. After factoring in more customary arguments for margin (e.g., part-to-part and lot-to- lot differences in response) the suggestion of additional factors of two or greater for each of these other proton specific sources usually comes as quite a shock to the design engineer. Resolution of these issues varies from program to program, usually with some element of compromise and the hope that either the components easily meet the requirements with margin or the design can be modified to accommodate the anticipated degradation. It is important that both the radiation effects specialist and the design engineer realize the needs for margin and not fall into the trap of assuming that the factor of 2 applied for environment uncertainty also accommodates uncertainties from other sources such as the response model. 2.3.5 Nonstandard Parts and Waivers: Every flight project design effort tracks parts that do not meet requirements with margin or that require "special" considerations. Often, IV-14 additional testing is required and special considerations are needed to evaluate risk. Nowadays, with the emergence of displacement damage concerns in Light Emitting Diodes (LEDs), optocouplers, and CCDs, many proton radiation effects are dealt with in this forum. As specifications of proton environments and requirements improve, along with predictive models for the environments and device responses, these issues will likely be dealt with on a more routine basis and 