ar testing in years prior to the NASA model development. The population of trapped electrons in the outer belt region are more accurately modeled by AE8, but the dynamic nature of this environment resulting from injection events must be considered. The NASA Space Environments and Effects (SEE) Program has recently released the NOAAPRO model which is intended to address the major shortcoming indicated above for the AP8 model in the altitude range of 250 kilometers to 850 kilometers. This model is not intended to replace AP8, but moreover to provide enhanced modeling capability for low orbit missions. Data from the CRRES and APEX satellite missions have been used to produce additional models of the trapped radiation environment which are available to the analyst for assessment and modeling of the charged particle environment. Galactic cosmic ray heavy ion particle flux modeling typically utilizes the models incorporated into CREME. The uncertainty in these models is again expressed as a factor of two. CRRES mission data has been used to produce an additional model, CHIME, which is also available to the analyst for assessment and modeling of the GCR environment. 5.3.3 Performing Rate Estimate Calculations A number of methods and analysis software tools exist for performing single event upset rate calculations. All of the methods require characterization information about the device single event upset susceptibility, and the tools typically provide a set of models for the space environment. In addition to the cross section versus LET curve (or curve fitting parameters for standard equations used to describe this characteristic), additional information about the dimensions of the sensitive volume are necessary for some of the heavy ion single event upset models. Measurements at a series of angles of particle beam incidence enable the determination of sensitive volume thickness, and to estimate the dimensions of the funnel region. Correlation of on-orbit measurements of single event upset rate with predictions which we