RAPID/IES Calibration Status Rutherford Appleton Lab ESTEC Jackie Davies Arne Asnes Chris Perry Martin Carter Matt Taylor Max Plank, Lindau Aerospace Corp Pat Daly Bern Blake CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID This presentation will concentrate on the IES electron sensor CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID IES CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID IES IES is an integrating sensor which means it detects the total energy deposited in the SSD within a short interval. If no event occurs within the integration interval then get a zero signal level. There is a degree of electronic noise which results in a distribution of measurements around the zero level (this is called the pedestal). The position of the zero point varies as a function of count rate and temperature. CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID IES The instrument monitors the position of the pedestal so that shifts can be corrected on the ground. The pedestal position varies with different detectors which means that the energy thresholds vary. Spectral re-sampling is used to get all the detectors onto the same set of energy bins which is vital for construction of uniform 3D electron distributions. Due to aging or non-optimal configuration some pedestal counts may fall into the science channels. IES is susceptible to high fluxes of ions in the range 350-800 keV CAA cross cal meeting, ESTEC 14th May 2007

Pedestal channels Pedestal contamination

BEFORE AFTER Instrument configuration was changed in summer 2006 to provide better matched lower energy thresholds. This helps to avoid re-sampling artefacts with the L3DD data. But still issue over absolute calibration levels.

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal PEACE/RAPID Kappa fitting undertaken for a number of intervals The original study found that the fit is very sensitive Two similar distributions result in significant differences in the cross cal parameter. Tried using two kappa distributions (e.g. result of W-P interactions) We always find that the gap between energy ranges hinders direct comparison. CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal Questions highlighted at October Cross-Cal Should we be using the kappa fitting technique to determine the cross-cal parameters or just as a verification of the cross cal from other techniques? Answer: For normal science data, only the latter! Do the new PEACE inter-anode comparisons make any difference? Answer: Too early to say, only became available a few weeks ago. Can we use the IES test-mode histogram data to look for intervals where IES and PEACE have an energy overlap ~19 keV. Answer: In theory yes, but need to consider a number of factors! Anything else we can try? Answer: Looking back at ground cal and commissioning data and also looking at cross cal with other spacecraft under special circumstances (e.g. GLEs). CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal Should we be using the kappa fitting technique to determine the cross-cal parameters or just as a verification of the cross cal from other techniques? CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal Difficulties with cross-cal include Pile-up in IES (only important in high count rate regions) Multiple (kappa) populations give too many possible fitting options No energy overlap between PEACE and standard IES products Some hints of inaccurate e-cal in top PEACE and bottom IES channels Instruments on different spacecraft give similar results so any discrepancies likely to be systematic. PEACE Distributions from C2 and C4 look very similar in both PEACE and IES IES Bad E cal? CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal Can we use the IES test-mode histogram data to look for intervals where IES and PEACE have an energy overlap ~19 keV. Answer: In theory yes, but need to consider a number of factors! Using PEACE 3DXnP product and then spin averaging to give distribution best matched to IES histogram data. Only about 20 events over the entire mission when the count rates in IES high enough during histogram intervals. PEACE data on C1 and C3 is usually windowed such that highest energies are not returned (is 3DR an alternative?). PEACE inter-anode recalibrated data only just available. Currently working with two plasma sheet intervals 2003-09-03 & 2005-08-09 and a higher count rate interval at the edge of the ring current 2002-06-14. CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal Issues with using histogram mode data include: Pile-up in IES (as with normal data) Pedestal subtraction issues Energy efficiency fall-off Very limited dataset E fall-off important for direct comparision in the energy overlap range. (n.b. occurs above pedestal subtraction effects) Property of the detectors Will be the same for all detectors May depend on look direction (but second order effect) Expected to be stable with time Histogram points without pedestal being removed Fall off in energy efficiency? Power law tail Histogram point (dE ~2.2keV) pedestal removed IES BM Clean data from nearby spin Four sample averages (dE ~8.8keV) pedestal removed CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal Energy fall-off seen in commissioning and ground cal data. To first order can be expressed as a linear energy loss, increasing with decreasing energy. Eloss ~ 14 – 0.08E (E in keV) Currently investigating if this is sufficient to explain in-flight data or if there is an additional count rate efficiency term. This will allow (almost) direct comparison with PEACE for those few events where we have data. CAA cross cal meeting, ESTEC 14th May 2007

CAA cross cal meeting, ESTEC RAPID PEACE/RAPID Cross Cal Next steps: Complete the assessment of energy fall-off using ground cal and in-flight data. Look for differences in the off-axis detectors in each head. For 20 identified intervals investigate near energy overlap region to obtain relative PEACE/RAPID cal as a function of time. Use comparisons with other S/C to help verify IES absolute cal (e.g. 2006-12-13, B. Blake). Assess RAPID contribution to total moment sums in regions of hot plasma. 2006-12-13 GLE event, solar electrons without protons CAA cross cal meeting, ESTEC 14th May 2007