Comparison of EPHIN Rates Pre- and Post- Detector A Failure-mode On

The plots below show side-by-side comparisons of various EPHIN detector rates as a function of EPHIN sensor temperature from a time interval prior to commanding detector A failure-mode on and from time after that configuration change. Times when the observatory was likely to be in the Earth's radiation belts have been excluded. The time interval before the configuration change includes an extended period in which the observatory was in normal-sun-mode due to a reset of the spacecraft IU.

Based on input from Reinhold Mueller-Mellin of the EPHIN IPI team, we expected the "Post-" data in the electron channels to have a rate 6.88 times the "Pre-" channel small-geometry rate due to the geometry change. In addition the rate should include a contribution from protons and nuclei. The observed change in rates is much smaller, increasing by only a factor of ~1.4 in the E150 channel and ~1.5 in the E1300 channel. The individual detector rates do not show great differences between the two time intervals; so, it seems unlikely that the discrepancy between expecting a factor of 6.88 increase and seeing ~1.5 is due to environment.

Pre-Post-
E150 rate 2008-10 E150 rate Post-FMA On
E1300 rate 2008-10 E1300 rate Post-FMA On
Detector B0 rate 2008-10 Detector B0 rate Post-FMA On
Detector C rate 2008-10 Detector C rate Post-FMA On
Detector D rate 2008-10 Detector D rate Post-FMA On
Detector E rate 2008-10 Detector E rate Post-FMA On
Detector F rate 2008-10 Detector F rate Post-FMA On

Last modified: Tue Feb 10 17:14:09 EST 2009

Dr. Michael Juda
Harvard-Smithsonian Center for Astrophysics
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E-mail: mjuda@cfa.harvard.edu