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CODIF Status

CODIF Status. Lynn Kistler, Chris Mouikis Space Science Center UNH. Sept 15-17, 2002 Paris, France. Outline. H+ Efficiencies Temporal changes Current status O+ Efficiencies Temporal Changes Current Status Comparisons with HIA High rate correction (magnetosheath)

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CODIF Status

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

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

  3. H+ Efficiencies • Temporal Changes. • 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) • 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). • The product of these values gives the total efficiency. • The stop rate (SR) is not completely reliable, which gives some uncertainty in the final answer.

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

  5. SC1/FM8 Efficiencies stop start Single event 2000/9/01 2003/9/01

  6. SC3/FM6 Efficiencies stop start Single event 2000/9/01 2003/9/01

  7. SC4/FM7 Efficiencies stop start Single event 2000/9/01 2003/9/01

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

  9. SC1/FM8 total Efficiency Change

  10. SC4/FM7 total Efficiency Change

  11. SC3/FM6 total Efficiency Change

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

  13. 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.

  14. SC1/FM8 O+ Absolute Eff.

  15. SC3/FM6 O+ Absolute Eff.

  16. SC4/FM7 O+ Absolute Eff.

  17. 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. 2003.

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