ROSETTA SESAME-PP DATA CALIBRATION DESCRIPTION ============================================== Revisions --------- 2015-09-18 third issue Purpose ------- This document describes the calibration of the SESAME-PP data delivered in the SESAME-PP level 3 data set. Introduction ============ The calibration of SESAME-PP data is divided into 6 different groups: 1) Housekeeping data from PP Healthcheck and SESAME Healthcheck 2) Permittivity measurements using PP's active mode with on-board data processing 3) Plasma wave measurements using PP's passive mode with on-board data processing 4) Permittivity measurements with time series data from PP active test mode data 5) Plasma wave measurements with time series data from PP passive test mode data 6) Plasma wave monitor (LP) data from the additional sensor mounted on the DIM cube 1) Housekeeping data ================= The PP Healthcheck data are ADC values using each of the 8 analog multiplexer channels. The potential data are not calibrated to sensor potential values as the sole pre- amplifier amplification factors are temperature dependent. Packet type ID: 0x5000 Byte-No Meaning Calibration function Comment ----------------------------------------------------------------------------------- 12,13 LP N/A Fixed value 0xFFFF: no signal 14,15 ADC-Offset (x-128)/128 * 2.5 V 16,17 -2.5V ref. (x-128)/128 * 5 V Measured via 2:1 divider 18,19 +2,5V ref. (x-128)/128 * 5 V Measured via 2:1 divider 20,21 Pot.Diff (x-128)/128 * 5 V -Y foot minus +Y foot signal 22,23 +Y potential (x-128)/128 * 5 V amplified +Y foot signal (x-128)/128 * 117 mV calibrated potential at +20C 24,25 -Y potential (x-128)/128 * 5 V amplified -Y foot signal (x-128)/128 * 117 mV calibrated potential at +20C 26,27 Tx current (x-128)/128 * 2.2 uA Driven by +X-foot electrode 28,29 PEN current (x-128)/128 * 2.2 uA Driven by MUPUS-PEN electrode 30,31 APXS current (x-128)/128 * 2.2 uA Driven by APXS electrode The digital electronics current used inside the PP electronics is recorded in the SESAME Healthcheck packet and the SESAME Housekeeping packet SESAME HK: ID 0x83 cE_U1 x*0.0022 V +5V Digital voltage for PP 0xA7 PP_U1 x*0.002 V +5V measured by PP after ser.res. derived PP_I (DI_U1 - PP_U1)/11.1 A Serial resistor is 11.1 Ohm The same information is included in the SESAME HC science packet, generated by the command COM_HK, ID 0x7200 Packet ID: 0x7200 Byte-No Meaning Calibration function Comment ----------------------------------------------------------------------------------- 36,37 CE_U1 x*0.0022 V +5V Digital voltage for PP 32,33 PP_U1 x*0.002 V +5V measured by PP after ser.res. derived PP_I (DI_U1 - PP_U1)/11.1 A Serial resistor is 11.1 Ohm 2) Permittivity data after on-board processing =========================================== A sequence of 20 frequencies is measured, each using 3 different transmitter voltage amplitudes. A wavelet-based on-board algorithm extracts via digital filtering the used frequency range, then fits a sine wave of the used frequency to the measured current and potential difference data. Amplitudes and phase difference are recorded in the telemetry packet. Packet type ID: 6201 Byte-No Meaning Calibration function Comment ---------------------------------------------------------------------------------- 16,17 Electrodes Filter: 0x0700/256 Tx electrode A: 0=OFF,1=X,2=PEN Filter: 0x0070/16 TX electrode B: 0=OFF,2=PEN,3=APX Filter: 0x0007 Multiplexer channel for monitor 18,19 # frequencies N/A Defined in control table (20) --- +1,+2 Nominal freq. [Hz] The used frequency is slightly different, see look-up table no TM Tx voltage ampl 1st set: 9.86V Measurement is repeated 3 times per freq 2nd set: 9.86V/2= 4.93V with automatic amplitude adjustment /1, 3rd set: 9.86V/4= 2.47V /2 and /4 +3 Quality flag Filter: 0x01 # 0 Transmitter current >=255 Filter: 0x02 # 0 Transmitter current <= 0 Filter: 0x04 # 0 Pot.Diff. >= 255 Filter: 0x08 # 0 Pot.Diff. <= 0 Dependent on flag settings the amplitudes are underestimated +4 #of points/wave N/A Dependent on value the amplitudes have to be corrected Amplitude correction according to number of points/wave: 16 points: PPWC=0.96841 32 points: PPWC=1.36941 64 points: PPWC=1.93624 +5,+6 Phase x/16 deg Phase shift Rx-Tx *) +7,+8 Current amplit. x/256/PPWC * 2.2 uA Average amplitude with correction +9,+10 Potent. amplit. x/256/PPWC * 119 mV Calibration for +20C *) A frequency dependent phase correction has to be applied. See the end of the file 3) Plasma wave measurements after on-board processing ================================================== Usually 8192 samples are measurd via the differential receivers and analysed on board by a wavelet algorithm, which calculates up to 10 power spectrum bins, distributed logarithmically across the frequency spectrum from 10 kHz to 20 Hz. Details of the measurement are defined in the control table and reported in the TM packet. Packet type ID: 6301 Byte-No Meaning Calibration function Comment ---------------------------------------------------------------------------------- 16,17 LP integrator LP_Int/5000000 s Integration time unit increment 18,19 LP value x*LP_integrator s Integration time, timeout FFFF 22,23 Time Increment (ADC_CLK_DIV+1)/5000 ms 1/sampling frequency 24,25 NSAMP 2^x Value between 10 and 13 28,29 NBIN N/A Number of frequency bins +1..+4 Spectrum bin P=x^2/(4*N) Spectral power in bin. N=NSAMP*(2^-i), i=1..NBIN Power density per bin i: PDi = Pi/bwi bwi=bandwidth of bin i: bwi=5000000/ADC_CLK_DIV/4/i Voltage Density VDi = SQRT(PDi)*0.934 mV/SQRT(Hz) 4) Permittivity measurements with time series ========================================== Only one frequency with a command-defined transmitter amplitude is measured. Both current and potential difference time vectors are included in the telemetry packet together with the on-board processed data. If the monitor channel of the electrode parameter is anything but 1, 2 or 4 the processed data are meaningless. Packet type ID: 6B04 Byte-No Meaning Calibration function Comment ---------------------------------------------------------------------------------- 14,15 Electrodes Filter: 0x0700/256 Tx electrode A: 0=OFF,1=X,2=PEN Filter: 0x0070/16 TX electrode B: 0=OFF,2=PEN,3=APX Filter: 0x0007 Multiplexer channel for monitor 16,17 Nominal freq. [Hz] The used frequency is slightly different, see DAC_ADDR calibration 18 NWAVE N/A Number of waves generated 19 TXAMP 2^(-x) Amplitude damping factor 20,21 ADC_DIV RXSAMP=5000000/(ADC_DIV+1) Receiver sampling frequency 22,23 ADC_ADR NSAMP=(ADC_ADR-255)/2 Size of Rx or Tx data vector 24,25 DAC_DIV TXSAMPF=5000000/(DAC_DIV+1) Transmitter sampling frequency 26 NSPW N/A Number of points/wave (16,32 or 64) 27 DAC_ADDR NDAC=DAC_ADDR+1 Number of DAC Values F=TXSAMPF/(DAC_ADDR+1) Actual transmitter frequency Data vector time increment: NSAMP/RXSAMP Relative DAC table sample time: (n-1)*1/TXSAMPF First time offset = 0 30-285 DAC table A=(x-128)/128*20 V Voltage difference between transmitter electrodes. With only 1 electrode (table 1): only 50% 286,287 NSAMP (NSPW+1)*NWAVE redundant with ADC_ADDR +1 Tx current (x-128)/128 * 2.2 uA Transmitter current through selected electrode (if 1,2 or 3) +2 Rx voltage diff (x-128)/128 * 119 mV Calibration for +20C +3 Quality flag Filter: 0x01 # 0 Transmitter current >=255 Filter: 0x02 # 0 Transmitter current <= 0 Filter: 0x04 # 0 Pot.Diff. >= 255 Filter: 0x08 # 0 Pot.Diff. <= 0 Dependent on flag settings the amplitudes are underestimated +4 #of points/wave N/A Dependent on value the amplitudes have to be corrected Amplitude correction according to number of points/wave: 16 points: PPWC=0.96841 32 points: PPWC=1.36941 64 points: PPWC=1.93624 +5,+6 Phase x/16 deg Phase shift Rx-Tx *) +7,+8 Current amplit. x/256/PPWC * 2.2 uA Average amplitude with correction +9,+10 Potent. amplit. x/256/PPWC * 119 mV Calibration for +20C *) A frequency dependent phase correction has to be applied. See the end of the file 5) Plasma wave measurements with time series ========================================= Usually 8192 samples are measurd via the differential receivers and analysed on board by a wavelet algorithm, which calculates up to 10 power spectrum bins, distributed logarithmically across the frequency spectrum from 10 kHz to 20 Hz. Details of the measurement are defined in the control table and reported in the TM packet. Additionally the complete data vector is included in the telemtry packet for detailed ground analysis. Packet type ID: 6C01 Byte-No Meaning Calibration function Comment ---------------------------------------------------------------------------------- 14,15 LP integrator N/A Value between 0 and 15 16,17 LP value x*LP_Int/5000000 s Integration time, timeout FFFF For calibration to wave amplitude see 6) 20,21 ADC_CLK_DIV N/A Default 125 for 40 kHz sampling 22,23 NSAMP 2^x Value between 10 and 13 24,25 Error Code time offset previous +(ADC_CLK_DIV+1)/5000 ms First value = 0 +1 pot.diff value (x-128)/128 * 119 mV Calibration for +20C ..... +1,+2 NBIN N/A Number of frequency bins +1..+4 Spectrum bin P=x^2/(4*N) Spectral power in bin. N=NSAMP*(2^-i), i=1..NBIN Power density per bin i: PDi = Pi/bwi bwi=bandwidth of bin i: bwi=5000000/ADC_CLK_DIV/4/i Voltage Density VDi = SQRT(PDi)*0.934 mV/SQRT(Hz) 6) Plasma wave monitor (LP) ======================== The wire sensor is biased with 0 V and sensitive only for external plasma waves with frequencies between 10 Hz and 50 kHz. When a measurement is started an integrator is emptied and a clock started. Any incoming plasma wave is charging the integrator. Once a lower threshold is passed the clock is reset and stopped again when an upper threshold is reached. The resulting clock value is transmitted as measurement value. A programmable clock divider can be used to slow the clock and thereby increase the sensitivity of the system. Packet type ID: 5100 Byte-No Meaning Calibration function Comment ---------------------------------------------------------------------------------- 14 nom.clock div CLK=5000000/2^x Integrator clock 15 actual clock div 16,17 measurement T=x/CLK Used integration time timeout 0xFFFF = 65535 repeated 16 times with increasing clock divider from 0 to 15. The last mesurement with divider 15 is repeated. Wave amplitude calibration: A=145*e^(-(x*2^CLKDIV-171)/2.6) mV Lookup-table for active measurement frequency correction ======================================================== Nominal freq. Actual frequency [Hz] -------------------------------- 10080 9746,59 6510 6385,70 2948 2870,26 758 751,20 409 406,90 146 145,76 74 73,98 Frequency dependent phase correction: ==================================== All phase shift components are listed with respect to the first sampled point of the data vector and are given in degrees. Nominal freq. Curr.Meas. Potential Meas. X PEN APXS +Y -Y dY ------------------------------------------------------------ 47 - 0.7 - 0.7 - 0.7 +12 +12 +12 146 - 1.3 - 1.3 - 1.3 + 8 + 8 + 8 409 - 2.9 - 2.9 - 3.0 + 2.9 + 2.9 + 2.9 758 - 4.7 - 4.7 - 5.0 + 0.8 + 0.8 + 0.8 2948 -17.1 -17.5 -18.1 - 2.6 - 2.6 - 1.9 6510 -39.5 -41 -44 - 5.8 - 5.8 - 3.9 10080 -67 -69 -73 - 8.7 - 8.7 - 5.8 The correct phase difference can be calculated by adding the relevant current measurement and potential measurement phase offsets to the measured value.