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THEMIS SWT August 6th-8th, 2007 meeting THEMIS SWT August 6th-8th meeting SCM operations and first results SCM team (CETP-Vélizy, France) : Co-i’s: A.

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Presentation on theme: "THEMIS SWT August 6th-8th, 2007 meeting THEMIS SWT August 6th-8th meeting SCM operations and first results SCM team (CETP-Vélizy, France) : Co-i’s: A."— Presentation transcript:

1 THEMIS SWT August 6th-8th, 2007 meeting THEMIS SWT August 6th-8th meeting SCM operations and first results SCM team (CETP-Vélizy, France) : Co-i’s: A. Roux, O. Le Contel Technical Manager(*): C. Coillot Lead Engineer: A. Bouabdellah Technicians: D. Alison & S. Ruocco Software Engineer: P. Robert THEMIS team support for software and commissioning: K. Bromund (GSFC/NASA) C. C. Chaston (SSL, UCB) C. Cully (CU) (*) SCM team thanks Bertrand de la Porte, the first technical manager, for his continuing support.

2 THEMIS SWT August 6th-8th, 2007 meeting The SCM 3-axis antennas are located at the end of a 1 meter SCM boom Magnetic components: 3 analogs signals from 0.1 Hz to 4kHz. Sensitivity: 0.8pT/  0.02pT/  Weight: 570 g Pre-amplifier (in 3D technology), located inside s/c body. Weight: 200 g Power: 75 mW PA + sensors: First vibrations, thermal cycling tests at CETP and then at UCB/JPL on the s/c. Fully calibrated at CETP quiet facility near Chambon la Forêt. SCM overview (I)

3 THEMIS SWT August 6th-8th, 2007 meeting Calibration mode A Triangular signal generated by the PA, is applied to the feedback winding installed around each antenna. Once per orbit a calibration is run for 30 seconds (default). After 60 seconds, the calibration is automatically turned off. Operation modesIDPU Data type# Comp.# FrequenciesAPIDSample rate S/s (nominal) Slow survey (SS) Relative allocation: 50% (12h P3,P4,P5) DFB filter banks1 to 2 (1)1 to 6 (6) to 8 (0.25) Fast survey (FS)DFB filter banks1 to 2 (1)1 to 6 (6) to 8 (4) RA: 50 % (10,8h)DFB waveform to 256 (8) Particle burst (PB)DFB waveform to 256 (128) RA: 10% of FS (1,2h)DFB spectra (Bpara & Bperp) 1 to 4 (2)16 to 64 (32) 44D0.25 to 8 (1) Wave burst (WB) RA: 1% of PB (43 s) DFB waveform3 44C512 to (8192) DFB spectra1 to 4 (2)16 to 64 (64)44F0.25 to 8 (8) SCM overview (II)

4 THEMIS SWT August 6th-8th, 2007 meeting SCM calibration process (I) New continuous calibration method delivered by K. Bromund called “ thm_cal_scm.pro ” with support from P. Robert Different possible ouputs (step parameter): # 0: counts, NaN inserted into each gap for proper ‘tplotting’ # 1: Volts, spinning sensor system, with DC field # 2: Volts, spinning sensor system, without DC field # 3: nTesla, spinning sensor system, without DC field # 4: nTesla, spinning SSL system, without DC field # 5: nTesla, fixed DSL system, without DC field, filtered

5 THEMIS SWT August 6th-8th, 2007 meeting SCM calibration process (II) Description of calibration method steps 0-2 # 0 - TM data in counts, separated into gap-free batches of data at same sample rate. For each gap-free batch, apply the steps 1-6 : # 1 - TM data in volts. ( tplot variable with '_volt' suffix) # 2a - remove spin tone using (interpolated) spin frequency from beginning of batch. o Spin period assumed constant for batch, but not assumed constant for full day. o Sliding spin fit to N_spinfit (  2) complete spins, using sliding Hanning window. o Bdc and misalignment angle calculated from spin fit centered around each point o DC field for data within one spin period of the edges is calculated using spin fit to first/last two spin periods of the batch. o output Bdc and misalignment angle as tplot variables with '_dc' and '_misalign‘ suffix, respectively. o subtract Bdc (in spin plane) from x, y, and z signals. b - detrend (optionally substract boxcar average by fixing the detrend frequency parameter Fdet.) c - clean spin harmonics, power current signals, (to be detailed later)

6 THEMIS SWT August 6th-8th, 2007 meeting # 3 - convolve with impulse response ( converts volts -> nT ) o get impulse response by taking inverse FFT of 1/gain(f) * [optional rectangular frequency filter] then divide by nk. nk can be an input parameter or derived from sample rate of batch and input parameter mk. o Get kernel suitable for use as FIR filter by shifting by nk/2, applying Hanning window. o Convolve kernel with data: Note: IDL convol function assumes that the center of the kernel is at index nk/2, so no delay is introduced. Edge behavior determined by /edge_zero, /edge_wrap, or /edge_truncate. With no /edge keyword, set all data within nk/2 samples of the edge to zero. # 4 - rotate from spinning sensor system to SSL # 5 - transform calibrated waveform to DSL using interpolated spin phase, which is calculated from the derived sun pulse data. # 6 - add Bx and By DC field from step 2a. use thm_cotrans to transform step 5 output to other coordinates (GSM, GSE) SCM calibration process (III) Description of calibration method steps 3-6

7 THEMIS SWT August 6th-8th, 2007 meeting In flight scm data are perturbed by two types of noise: 1) spike at 2 f0 (f0 being the spin frequency) and its harmonics due to power ripples 2) 8/32 Hz tones which correspond to numerous instrument clocks Fortunately these noise are both constant in amplitude and phase locked 1) spike at 2f0 is phase locked relative to the spin phase 2) 8/32 Hz are phase locked to 1s clock (C. Cully’s report) C. Chaston has shown that a cleanup based on a superposed epoch analysis (SEA) is very efficient Currently two versions are available and give good results: thm_cal_ccc.pro using a cleanup routine written by C. Chaston thm_cal_ole.pro using cleanup routine written by O. Le Contel Both routines perform successively two SEA: 1) First SEA with an averaging window equal to the spin period (fixed from state file data) 2) Second SEA with an averaging window equal to a multiple of 1s (keyword wind_dur_1s = 3.) SCM calibration process (IV) Details about cleanup process

8 THEMIS SWT August 6th-8th, 2007 meeting Both routines are included in thm_cal_scm (thm_cal_scm_ccc or thm_cal_scm_ole) at step 2c and can be actived by the same keywords: a)cleanup =‘spin’ for only cleanup of 2f0 tone b)cleanup =‘full’ for full cleanup with an additional keyword wind_dur_1s fixing the duration of the second averaging window c)commented cleanup keyword corresponds to no cleanup Example: SCM calibration process (V) Details about cleanup process thm_cal_scm_ole, probe=satname, datatype=mode+'*', out_suffix = '_cal', $ trange=trange, $ ; nk = 512, $ ; mk = 4, $ ; Despin=1, $ ; N_spinfit = 2, $ cleanup = ‘full',$ wind_dur_1s = 1.,$ ; Fdet = 2., $ ; Fcut = 0.1, $ Fmin = 0.45, $ ; Fmax = 0., $ step = 4, $ /edge_zero

9 THEMIS SWT August 6th-8th, 2007 meeting SCM calibration process (VI) Example of cleanup process A B C D E F A: raw waveform in volts B: despinned waveform and spectrum in dBV/sqrt(Hz) C: Spin phase locked noise built by SEA an spectrum D: cleaned (only power ripples) waveform and spectrum E: 1s phase locked noise (SEA) F: Fully cleaned waveform and Spectrum Note that it remains some spikes which are not phase locked B C D E F 8 Hz 32 Hz 2&4 f0 tha on April 8th 2007 between UT

10 THEMIS SWT August 6th-8th, 2007 meeting Physical quantities (L2 data): In SSL, DSL, GSE, GSM and other coordinates FS waveforms (scf) of Bx, By, Bz [8 S/s; Allocation~ 10.8h depending on which probe] PB waveforms (scp) [128 S/s; All.~ 1.2h] WB waveforms (scw) [8192 S/s; All.~ 43s] Filterbank data (fbk) [1comp.; 6 freq.] throughout orbit PB spectra (ffp) [2 comp.; 32 freq.] WB spectra (ffw) [2 comp.; 64 freq.] SCM science data (I)

11 THEMIS SWT August 6th-8th, 2007 meeting L2 subset: Magnetic field aligned frame (MFA) Minimum variance frame (MVA) Polarization analysis Using FFT and assuming .  B =0 and k   we can get the k direction and the directions of the axis of the polarization ellipse SCM science data (II) K direction z B0B0 kk kk   Major axis direction X close Sun direction

12 THEMIS SWT August 6th-8th, 2007 meeting First results: substorm event March 23rd UT Particle burst mode period on thd Electromagnetic waves with frequencies up to 10 Hz are detected at each dipolarization associated with a change of sign of the electron velocity and an increase of particle density What about e- distribution functions and parallel/perpendicular to B e- fluxes? Bx By Bz B Ions Burst data Ni Vi Ti e- burst data Ne Ve Te Scp data Hz

13 THEMIS SWT August 6th-8th, 2007 meeting First results: FTE event May 20th UT Fast survey mode period Electromagnetic waves with frequencies up to 4 Hz are detected within the FTE Bx By Bz B Ions reduced data Ni Ti e- reduced data Vi Scf data Hz

14 THEMIS SWT August 6th-8th, 2007 meeting First results: HFA event July 4th UT Fast survey mode period No Electromagnetic waves within HFA But EM waves with frequencies up to 4 Hz are detected at the edges Bx By Bz B Ions reduced data Ni Ti e- reduced data Vi Scf data Hz

15 THEMIS SWT August 6th-8th, 2007 meeting First results: MP crossing event June 19th UT Particle burst mode period on thc Frequency of em waves increases as thc leaves the magnetosphere and enters in the boundary layer Maximum of waves amplitude corresponds to variations of e- velocity What about EFI data ? Bx By Bz B Ions burst data Ni Ti e- burst data Vi Scp data Hz Ne Ve Te


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