lacement damage resulting from any specified space environment or proton fluence at a given test energy. In fact, it was initially introduced as a "non-ionizing rad", or NIRad(Si), as part of an introductory tutorial for the non-radiation effects personnel in the astronomy community. They were the first to attempt using extremely high quality scientific CCDs in demanding space applications. Since the concept of an ionizing rad(material) is generally familiar to design engineers, it is a useful way to implement a displacement damage analysis tool. Within the radiation effects community, equivalent displacement effects have long been expressed in terms of 1 MeV neutron equivalence [see Mess86, Gove84]. In the last decade, several groups have advocated the usage of various proton energies as the MeV-equivalent comparison of choice. However, the best energy choice is made by consideration of the transported damage-weighted proton spectrum that is very dependent on the shielding material and thickness. For example, a 10 MeV-equivalent proton "standard" might be used for a thinly shielded solar cell project, whereas a 60 MeV- equivalent proton "standard" might be chosen for a heavily shielded CCD study. As discussed below, displacement damage can easily be compared in terms of "equivalent proton fluences" at one of these specified energies. Whether one chooses to perform a displacement damage analysis in terms of displacement damage dose or a MeV- equivalent fluence, it is very important to identify the damage function employed since the final result can depend critically on this choice. 2.4 On-Orbit Performance Predictions In this section, we will first describe a method for performing space predictions based on the concept of displacement damage dose described above. In practice, it is useful to consider two important cases. In the first, the device parameter of interest (e.g., CCD CTE or dark current) varies linearly with proton fluence (i.e., can be characterized by a damage factor). In the second, the device prope