ROSETTA ROMAP DATA CALIBRATION DESCRIPTION =========================================================================== Revisions --------- 2009-04-20 first issue, IGeP 2015-06-30 update for comet phase, IGeP Purpose ------- This document describes the calibration of the ROMAP-MAG and ROAMP-SPM data delivered in the ROMAP level 3 data set. ROMAP-MAG calibration ===================== Introduction ------------- There are 2 kinds of calibrations applied to the ROMAP-MAG raw data: 1) Preliminary calibrated magnetometer data (draft aligned and very draft offset corrected). 2) Final calibration (cleaned from offset and spacecraft disturbances, done by TU-BS using RPC data). Only some selected data intervals are provided to PSA during cruise. The cleaning procedure consists of the following steps: - Disturbances which can be identified as lander supply current related are removed first. Only stepwise switched currents can be removed. The step height is determined as good as possible, Step times are determined and a function with constant bias fields between step times is created which is subtracted from the original data. - High frequency disturbances are identified by evaluation of dynamic spectra. If significant high frequent disturbances can be identified (during cruise in always due to reaction wheels) data are filtered down to 1Hz data (0.5Hz corner frequency) - Interferences due to orbiter sources are determined by comparison of RPC-MAG and ROMAP data. If signals occurs at both sensors with different signal amplitude (can be seen in difference) the ratio is determined, the disturbance signal is scaled for both sensors and the scaled signals are subtracted from the data. - Finally the offsets are determined with best effort. For that a solar wind analysis is used. For flybys solar wind data before and after are needed to interpolate the offset during flyby. Only final level 3 data, no intermediate products or correction functions are archived. Level 3 data are only produced for selected time intervals (e.g. Mars flyby, Steins flyby). Preliminary calibration (level 3 A, B and C) ----------------------------------------------- The preliminary calibration is used during cruise phase when the sensor head boom is stowed. The calibration parameters are the rotation matrix (from ROMAP sensor system to Lander system and Orbiter system) and the offset vector. The offset vector is generally time dependent. However, unless otherwise specified, a constant offset vector is used. In the level 3 data the disturbances due to MUPUS instrument are not removed. Level 3 A --------- Calibration in ROMAP system (R). Boom stowed. (BRx_cal) ( 1 0 0 ) (BRx + 700 ) (BRy_cal) = ( 0 1 0 ) . (BRy + 1400 ) (BRz_cal) ( 0 0 1 ) (BRz - 1100 ) where BR_cal is the calibrated magnetic field vector in the ROMAP system. BR is the raw magnetic field vector in the ROMAP system. The unit for BL, BR, BR_cal and offset is nT. Level 3 B --------- Calibration in the Lander system (L). Boom stowed. (BLx_cal) ( 0 0.33569 -0.94197 ) (BRx + 700 ) (BLy_cal) = ( 1 0 0 ) . (BRy + 1400 ) (BLz_cal) ( 0 0.94197 0.33569 ) (BRz - 1100 ) Calibration in the Lander system (L). Boom deployed. (BLx_cal) ( 0 1 0 ) (BRx - 38 ) (BLy_cal) = ( 1 0 0 ) . (BRy - 102 ) (BLz_cal) ( 0 0 1 ) (BRz - 102 ) where BL_cal is the calibrated magnetic field vector in the Lander system BR is the raw magnetic field vector in the ROMAP (sensor) system : The unit for BL, BR, BL_cal and offset is nT. Level 3 C --------- Calibration in the S/C (Orbiter) system. Boom stowed. The calibrated magnetic field vector in the Orbiter system (BO) is given by the following transformation of the magnetic field vector in the ROMAP system (BR): ( 0 -0.3357 0.942 ) Bs/c_cal = ( -1 0 0 ) . (BR - Boffset) ( 0 0.942 0.3357 ) Calibration in the S/C (Orbiter) system. Boom deployed. (BLx_cal) ( 0 -1 0 ) (BRx - 38 ) (BLy_cal) = ( -1 0 0 ) . (BRy - 102 ) (BLz_cal) ( 0 0 1 ) (BRz - 102 ) where Bs/c_cal is the calibrated magnetic field vector in the S/C system BR is the raw magnetic field vector in the ROMAP (sensor) system Boffset is the offset vector in ROMAP system. The unit for BR, Bs/c_cal and Boffset is nT. The offsets used for converting data from CODMAC level 2 to CODMAC level 3 (C type files in ROMAP notation) and the corresponding data products are listed below. Mars phase: MAG_FSC_060829181608_00087 MAG_FSC_061128162210_00088 ( -900) Boffset= (-1400) ( 1050) MAG_FSC_061206010011_00009 MAG_FSC_061206011057_00018 MAG_FSC_061206013312_00009 MAG_FSC_061206014352_00018 ( -900) Boffset= (-1440) ( 1070) MAG_FSC_061206070011_00009 MAG_FSC_061206071051_00018 MAG_FSC_061206073311_00077 ( -895) Boffset= (-1435) ( 1066) MAG_FSC_061207030011_00029 MAG_FSC_061207033312_00697 ( -885) Boffset= (-1405) ( 1054) MAG_FSC_061208000208_00121 MAG_FSC_061208034806_00039 MAG_FSC_070224010108_02212 MAG_FSC_070522142206_00121 ( -900) Boffset= (-1400) ( 1050) Steins phase: MAG_FSC_080904183821_02039 ( -550) Boffset= (-1800) ( 1200) Post Hibernation phase and Pre Delivery Calibration Science: For all data ( -800) Boffset= (-1500) ( 1000) The achieved data quality is level 4 (>100nT) except for MAG_FSC_140417025012 ( -876) Boffset= (-1481) ( 953) MAG_FSC_140714030507 ( -778) Boffset= (-1440) ( 955) MAG_FSC_140908005005 ( -810) Boffset= (-1550) ( 1010) MAG_FSC_140915131506 ( -810) Boffset= (-1550) ( 1010) MAG_FSC_140925055006 ( -810) Boffset= (-1550) ( 1010) MAG_FSC_141006204506 ( -800) Boffset= (-1550) ( 1010) MAG_FSC_141016211506 ( -800) Boffset= (-1550) ( 1010) for all sequences with specific offsets the achieved data quality is level 3 (<100nT) Separation/Descent/Landing and Rebounds: all ( 38) Boffset= ( 102) ( 102) The achieved data quality until boom deployment at 08:56:30 is level 4 (>100nT)and later level 2 (<10nT) Level 3 D --------- Calibration in the ECLIPJ2000 system before Lander release and in CSEQ after Lander release. Boom stowed. The magnetic field vectors are transformed from orbiter system (level 3 C) to the ECLIPJ2000 reference frame before Lander release and to CSEQ after Lander release. The rotation matrix is time dependent. Final calibration (level 5 E, F and G) -------------------------------------- All level 5 data have a quality level of 1 (<5nT) Level 5 E --------- Final calibrated data, in physical units, cleaned from offset and spacecraft disturbances, in MAG (magnetometer) coordinates Level 5 F --------- Final calibrated SC data, in physical units, cleaned from offset and spacecraft disturbances, in Lander coordinates Level 5 G --------- Final calibrated SC data, in physical units, cleaned from offset and spacecraft disturbances, in S/C coordinates Level 5 H --------- Final calibrated SC data, in physical units, cleaned from offset and spacecraft disturbances, in ECLIPJ2000 coordinates before Lander release and CSEQ after Lander release. ROMAP-SPM calibration ===================== Introduction ------------- The level 3 calibration consists of: - conversion of ion energy and angle distributions in cm-2*s-1, - conversion of Faraday cup currents in nA, - conversion of energy in eV - conversion of angle (elevation) in degrees. The ion currents are left in ADC units (signed 16 integers) since the CEM amplifications are not yet clear. Energy and angle conversion --------------------------- The energy tables and the correspondences between step numbers and energy and between step numbers and angle (elevation) are given in the following tables. Correspondence between step number and elevation: Step No 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Ion1/2 (deg) -52 -47 -41 -34 -27 -21 -16 -11 -6 0 5 10 15 20 25 31 Correspondence between step number and energy: Step No "64" 0 1 2 3 4 5 6 7 8 9 10 11 Step No "32" 0 1 2 3 4 5 Ion1/2 (eV) 38.6 42.6 46.6 50.6 54.6 59.9 65.3 70.6 77.3 83.9 90.6 98.6 Electron (eV) 0.35 0.42 0.49 0.56 0.63 0.7 0.84 0.98 1.12 1.3 1.47 1.75 Step No "64" 12 13 14 15 16 17 18 19 20 21 22 23 Step No "32" 6 7 8 9 10 11 Ion1/2 (eV) 107 117 127 138 150 163 178 194 211 230 250 271 Electron (eV) 2.03 2.38 2.74 3.16 3.72 4.28 4.98 5.82 6.73 7.79 9.05 10.5 Step No "64" 24 25 26 27 28 29 30 31 32 33 34 35 Step No "32" 12 13 14 15 16 17 Ion1/2 (eV) 295 321 350 381 414 450 490 533 580 640 700 760 Electron (eV) 12.3 14.2 16.5 19.2 22.3 25.9 30.1 34.9 41.0 47.4 54.7 63.1 Step No "64" 36 37 38 39 40 41 42 43 44 45 46 47 Step No "32" 18 19 20 21 22 23 Ion1/2 (eV) 820 900 980 1060 1160 1260 1360 1480 1620 1760 1920 2080 Electron (eV) 73.7 86.3 100 116 135 156 181 211 245 284 330 383 Step No "64" 48 49 50 51 52 53 54 55 56 57 58 59 Step No "32" 24 25 26 27 28 29 Ion1/2 (eV) 2260 2460 2680 2920 3180 3460 3760 4080 4440 4820 5260 5720 Electron (eV) 445 517 600 695 810 937 1095 1274 1474 1716 1989 2316 Step No "64" 60 61 62 63 Step No "32" 30 31 Ion1/2 (eV) 6220 6760 7360 8000 Electron (eV) 2684 3115 3621 4210 Step No "64" 0 1 2 3 4 5 6 7 8 9 Step No "32" 0 1 2 3 4 Far.Cup -"Ions" (eV) 10.7 12.7 15 17.6 20.8 24.6 29.2 34.6 40.8 48.6 Far.Cup -"Electrons" (eV) 1 2 Step No "64" 10 11 12 13 14 15 16 17 18 19 Step No "32" 5 6 7 8 9 Far.Cup -"Ions" (eV) 57.6 67.8 80.2 95.2 113 133 160 190 224 264 Step No "64" 20 21 22 23 24 25 26 27 28 29 Step No "32" 10 11 12 13 14 Far.Cup -"Ions" (eV) 314 370 440 520 614 730 864 1020 1204 1430 Step No "64" 30 31 Step No "32" 15 Far.Cup -"Ions" (eV) 1690 2000 Conversion of ion energy and angle distributions (ion 1 and ion 2) ------------------------------------------------------------------ N[particles/cm-2/s]= C/S/T Where C represent the counts (read from telemetry). S is the ion detector surface: ion1: 0.08 cm-2 ion2: 0.1 cm-2 T is the exposition time (read from the header of the ROMAP TM packets) short: 0.04 s long: 0.2 s Conversion of Faraday cup currents ---------------------------------- The currents are given by the Ohm law, I=U/R, where R = 5.1e9 Ohm U is given by the ADC; the ADC input range is [-2 V, 2 V] and the output resolution is 16 bits. Thus, the following transfer function is applied: R = 5.1e9 Ohm; U = (4.0/65535.0)*Itm -2.0, where Itm is the raw current (read from telemetry, i.e. ADC output) Ifc [nA] = (U/R)*1e9;