Modeling the Chandra space environment

This paper describes the development of CRMFLX, an ion model for the outer magnetosphere developed for scheduling periods when the Advanced CCD Imaging Spectrometer (ACIS) instrument onboard the Chandra X-ray Observatory can be safely moved into the focal plane position required for science observations. Because exposure to protons with energies of approximately 100 keV to 200 keV has been shown to produce an increase in the charge transfer inefficiency (CTI) of the ACIS instrument a tool for predicting encounters with magnetospheric regions rich in these particles is required. The model is based on data from the EPIC/ICS instrument onboard the Geotail satellite and provides the user with flux values for 100 kev to 200 keV protons as a function of satellite position and the geomagnetic activity Kp index.