DMSP Dosimetry Data: A Space Measurement and Mapping of Upset Causing Phenomena

Data from the DMSP/F7 satellite dosimeter star event counters are presented. The DMSP dosimeter star event counters measure the number of pulses that exceed set energy deposition levels (40 MeV for three detectors and 75 MeV for the fourth detector) behind four different thicknesses of aluminum shielding. The term "star event" is used because linear energy transfer depositions above 40 MeV can be produced by high energy proton or heavy ion interactions with nuclei in the detector creating a star type release of energetic secondaries. The energy deposition that creates the high energy pulses in the detectors can come either directly from incident cosmic rays, directly from high energy protons that traverse long path lengths in the detector volume, indirectly from nuclear reactions in the detector created by incident high energy protons, or indirectly from nuclear reactions in the vicinity of the detector which create recoiling nuclei that deposit energy in the detector. These nuclear stars and direct energy pulses create single event upsets (SEUs) in microelectronic components in the near-Earth space environment. Here we will first describe the properties of the star channel of the dosimeter on DMSP/F7; then present the star count maps of the 840 km region of space; and finally discuss their relation to upset phenomena.