Randomly sampling the solar wind data sets provides a method of obtaining statistical estimates of the Chandra environment. This gives the satellite position and radial distance in GSE coordinates as a function of time for use in the probability calculations described below. Further verification will be required to ensure that the orbit propagation software is compatible with that used by the Chandra program in producing ephemerides for time tagging satellite commands. Instead, typical Parker spiral IMF values were used for the cases examined here. The bow-shock model used is adapted from Bennett et al.
Counters track the number of times each satellite location encounters a given region.
This process is repeated for the specified number of random draws, in this case, 1000. The probability that a given location in space is in one of the three regions is then simply the fraction of encounters with that region. In the future, it may be desirable to increase the number of random samples to sample more fully the parameter space of variations in the solar-wind plasma parameters. A more detailed simulation of the magnetosphere's particle flux will be needed when Chandra's orbit takes it through the geotail and it spends a greater fraction of its time within the magnetosphere. Superimposed on the probability curves are the periods of Chandra ACIS safing as provided by S. Virani.