CODIF Status Lynn Kistler, Chris Mouikis Space Science Center UNH Sept 15-17, 2002 Paris, France

Outline H+ Efficiencies l Temporal changes l Current status O+ Efficiencies l Temporal Changes l Current Status Comparisons with HIA High rate correction (magnetosheath) Spillover Subtraction Radiation Belt Background subtraction

H+ Efficiencies Temporal Changes. l The temporal changes in the absolute efficiency are determined using the “Monitor Rates” –Start rate (SF) –Stop rate (SR) –Coincidence Rate (SFR) –Single event rate (SEV) l These allow us to monitor the start efficiency (SFR/SR), stop efficiency (SFR/SF) and the fraction of coincidences that also have a single position signal (SEV/SFR). l The product of these values gives the total efficiency. l The stop rate (SR) is not completely reliable, which gives some uncertainty in the final answer.

Temporal Changes To improve the declining efficiencies, we tried the following MCP voltage changes once the spacecraft were out of the SW/Magnetosheath: l June 28: SC1 and SC4 increased two steps. (values SC1/148, SC4/146) –Result - all OK, but not a big increase in efficiency l July 12: SC1 and SC4 increased another two steps (values SC1/150,SC4/148) –Result - increase in efficiency –Some PACC discharges on SC1 l Aug 23: SC1, SC3, SC4 increase two steps (SC1/152, SC3/150,SC4/150) –Result - discharges on all Spacecraft l Set new values to SC1 148 (+2), SC3 148 (+0), SC4 148 (+4)

SC1/FM8 Efficiencies start stop Single event 2000/9/012003/9/01

SC3/FM6 Efficiencies start stop Single event 2000/9/012003/9/01

SC4/FM7 Efficiencies start stop Single event 2000/9/012003/9/01

Efficiencies Temporal Changes (cont). l The changes in SC1(FM8) look realistic- we use these to get an absolute efficiency curve versus time l SC4(FM7) and SC3(FM6) SFR/SR is unreasonable - difficult to use to determine the total change with time. l To determine the changes in time for SC3 and SC4, we used comparisons with SC1(FM8).

SC1/FM8 total Efficiency Change

SC4/FM7 total Efficiency Change

SC3/FM6 total Efficiency Change

Efficiencies l There are some changes from older (April 2003) ABSEFF calibration files in the Nov-Dec 2001 time frame. l The shape of the curves has changed slightly so that the energy dependence matches HIA and agrees better with the measured Efficiency vs. Energy. l There is still an unresolved overall offset from HIA (Chris will show more). l These changes are now included in the Calibration files (ready, but not yet delivered to CESR) - they are good through ~Mar The summer changes have not yet been included.

O+ Efficiencies The O+ efficiencies have been completely redone. Because the monitor rate data, which give us the true efficiency measurement, measure everything coming in the instrument, we need to identify “pure” O+ time periods. To do this, we have used ~all times when O+ beams are observed in the polar cap - these time periods give us a true efficiency measurement for a particular angular pixel. To determine how the particular angular pixel compares with other pixels, we use inner magnetosphere time periods where there is significant O, and a gyrotropic distribution. Assuming gyrotropy, we can get the relative pixel efficiencies. We then take our “true” individual pixel measurements combined with our “relative” measurements to determine the average O+ efficiency as a function of time. Finally, as with H+, we concentrate on using SC1/FM8, and then get the SC3 and SC4 efficiencies by comparing the fluxes between spacecraft.

SC1/FM8 O+ Absolute Eff.

SC3/FM6 O+ Absolute Eff.

SC4/FM7 O+ Absolute Eff.

O+ comments O+ efficiency now decreasing faster at the beginning of the mission than previous assumed. The calibration files are all now available, but not yet submitted to CESR. They are good through Mar