to make a first principles calculation of the final stable proton induced defect inventory (defect types and quantities), and its effectiveness at causing CTE changes. (The exact value of this constant also depends on a particular imager design and the readout conditions as will be discussed in section 3.2.2.) Leicester (right ordinate) JPL (scale factor in text) 10-11 10-12 10-13 PROTON ENERGY (MeV) Figure 10 The NIEL is compared with experimental CTE damage factors. The data was normalized to NIEL at 10 MeV, and the scale factor values are 3.9x10-11 and 1.2x10-11 ACTEg(Si)/MeV for the Leicester (EEV) and JPL (Ford) CCDs, respectively. At higher energies, the data fall below the NIEL curve. The deviations from NIEL are consistent with those observed in figure 7 for a different set of devices. After [Dale93]. IV-71 Figure 10 also shows that the measured CTE damage factor falls below the NIEL calculation at higher energies, for reasons still not well understood (see section 3.2.2). In this example, we perform the on-orbit prediction using the theoretical NIEL calculation as the displacement damage function, in order to provide a conservative engineering estimate of performance. It turns out that the CTE degradation is over-estimated by a factor of two by using the NIEL dependence instead of the energy dependence of the measured damage factors. The final information needed for the on-orbit prediction is the differential proton spectral information, d(E)/dE, for the orbit and shield thickness in question. This is used to calculate the amount of displacement damage at each proton energy for the time period considered. The total damage follows from integrating the damage over all energies reaching the CCD as expressed below: ACTE(E) Note that the integral is simply the displacement damage dose in units of MeV/g when NIEL(E) is expressed in units of MeVcm2/g. The integration limits, E1 and E2, are defined and discussed with equation 5. Despite various mitigation approaches, for devices such as CCDs that are extremely s