CODIF Status Lynn Kistler, Chris Mouikis Space Science Center UNH July 6-8, 2005 Paris, France
Outline • H+ Efficiencies • O+ Efficiencies • Moments comparisons • Comparisons with FAST/TEAMS
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.
Temporal Changes • Following the last meeting, the MCP voltages were increased as follows: • July 12 and 24, 2004: All SC increased two steps. (values SC1/150, SC3/150, SC4/150) • Result - OK, on all spacecraft • Sept 25, 2004: All SC increased two steps (values SC1/152, SC3/152, SC4/152) • Result - some discharges in SC3 - reduced to 150 on 10/12/04
SC1/FM8 Efficiencies 1-year Whole mission stop start Single event 2000/9/01
SC4/FM7 Efficiencies 1-year Whole mission stop start Single event
SC3/FM6 Efficiencies 1-year Whole mission stop start Single event
Separate Anode Efficiencies • In order to accurately measure the velocities and pitch angle distributions, the efficiencies of individual anodes need to be known. • This is determined by using time periods when the ion distribution is expected to by gyrotropic, and normalizing the anodes so that they are the same at the same pitch angle.
SC3 Anode Efficiencies Feb, 2003 Anodes 5-8 are so far below the other anodes that it is almost impossible to calibrate them. In addition, including them adds spikes to the data, because one count converts to such a high flux. Therefore, we decided to no longer include anodes 5-8 when calculating fluxes. Any counts are zeroed, using the calibration files.
SC3 pitch angle distribution Note that SC3 still produces very good data using anodes 1-4. In most cases it still measures a complete pitch angle distribution (depends on field configuration). The main loss is the measurement of Vz.
Separate Anode Efficiencies Conclusions • SC4 and SC1 (up to the anomaly) • Difference between anodes can easily be accounted for in the calibration files. • For SC3 • the difference between anodes 1-4 and 5-8 is so big that we can no longer accurately determine the anode 5-8 efficiency. • Because the efficiency is so low, single counts observed on these anodes are calculated as a very high flux and introduce spikes on plots vs time • Anodes 1-4 are still quite good, and in most areas we still get complete pitch angle distributions using half the instrument. • Therefore, starting on Feb 24, 2003, we no longer include anodes 5-8. These anodes are zeroed out in the efficiency files. • Programs which calculated flux need to be changed so that the calculation assumes only anodes 1-4 are included.
O+ Efficiencies • Anode Efficiencies. • Anode efficiencies can be determined in exactly the same way they are for H+: by using time periods when the distribution is gyrotropic and there is sufficient O+ flux. This works well, and the results are similar to O+ • Absolute Efficiencies. • To determine absolute efficiencies, we need time periods when the composition is almost pure O+. To do this we use the time periods when we see O+ beams in the polar cap. • Since the beams are normally observed in only one anode, we then use the anode efficiencies to normalize the measurement to the whole instrument. • The beam procedure is done using SC1. We then use comparisons between SC to get the absolute efficiencies for SC3 and SC4.
SC1 O+ Efficiency O+ efficiency using O+ beam data
Plasma Sheet - 2003 CODIF H+ SC1, SC3, SC4 • The density shows a good agreement between all SC • The velocity components from SC3 don’t agree because only one hemisphere is used
Plasma Sheet - 2003 CODIF H+One hemisphere - Instrument coord. SC1, SC3, SC4 • Here moments from the 3 SC in instrument coordinates, calculated using the one hemisphere (top) are plotted • All moments show a good agreement confirming that the SC3 top hemisphere provides good data.
Plasma Sheet - 2003 CODIF O+1 – 40 keV – Instrument coord. SC1, SC3, SC4
Plasma Sheet - 2004 CODIF H+One hemisphere – Instrument coord. SC1, SC3, SC4
Plasma Sheet - 2004 CODIF O+1 – 40 keV – Instrument coord. SC1, SC3, SC4
2003 CODIF – HIA Comparison SC1 - CODIF, SC1 - HIA • Comparison between CODIF and HIA moments for SC1 • The density calculated by HIA, inside the magnetosphere, is lower by a factor of ~2 compared to the CODIF density • The velocity components show a good agreement
2004 CODIF – HIA Comparison SC1 - CODIF, SC1 - HIA
Efficiency Summary • H+ and O+ HS efficiencies have been calculated through the end of 2004. The files are available. • SC4 continues to operate very well • SC3 works well on one half. Using that half we can get reliable fluxes, densities, temperatures and pitch angle distributions. Vz cannot be measured. • SC1 worked very well until the anomaly. We hope that we will get it operating again soon.
Comparisons with FAST/TEAMS • The FAST/TEAMS instrument is almost identical to CODIF • It has been operating for almost 9 years - since August, 1996 • Comparisons with FAST/TEAMS will give us some idea what to expect in the extended mission.
FAST/TEAMS Efficiencies • After a significant increase in MCP voltage after the first year, the MCP voltage was kept constant for more than 3 years. Thus after 4 years, the efficiency had declined to 1% of the original value. • A series of increases in 2002 brought it up to a level where the instrument again took reasonable data. • After 8.5 years it is operating at about 6-10% of the original efficiency. • By occasionally increasing the voltage, the efficiency is being kept fairly constant • The FAST MCP voltage has increased 14% from 2.9 to 3.4 kV over the mission. CODIF has so far increased 7%.
Recent FAST Data (June 26, 2005) All-Ion Data Teams Data H+ He+ O+
Conclusions • Despite reduced efficiencies, TEAMS continues to provide composition information after almost 9 years. • In addition, because of the coincidence requirements, it continues to give reliable fluxes in the radiation belts, where the all-ion instruments cannot function. • We expect that CODIF on CLUSTER will similarly continue to perform for the duration of the extended mission.