SWGTemplate- 1 UCB, Nov 15/16, 2006 THEMIS SCIENCE WORKING TEAM MEETING Search Coil Magnetometer (SCM) team Co-i: A. Roux, O. Le Contel Technical Manager(*): C. Coillot Lead Engineer: A. Bouabdellah Technicians: D. Alison & S. Ruocco Software Engineers: P. Robert & (X) (*) SCM team thanks Bertrand de la Porte who was the first technical manager and for his continuing support. CETP-Vélizy, France

SWGTemplate- 2 UCB, Nov 15/16, 2006 SCM will measure the magnetic components of waves associated with substorm breakup. Wave signature is essential to identify the mechanism responsible for triggering breakup. Wave signatures are also expected to play a critical role in plasma transport through the magnetotail and across the magnetopause. SCM objectives

SWGTemplate- 3 UCB, Nov 15/16, 2006 The SCM 3-axis antennas are located at the end of 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 qualified at CETP (vibrations, thermal cycling) and then at UCB/JPL on s/c. Fully calibrated at CETP quiet facility near Chambon la Forêt. SCM overview (I)

SWGTemplate- 4 UCB, Nov 15/16, 2006 Calibration mode A Triangular signal generated by the PA and applied to a feedback winding installed in 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)

SWGTemplate- 5 UCB, Nov 15/16, 2006 SCM calibration processing (I) Waves calibration method 3) Production of "clean" raw waveforms in the spinning Sensor Coordinate System (SCS) 1) get Level 1 SCM waveform (in Volts ) 4 ) Calibration of each component and conversion in nT in the frequency domain (for the selected time interval) 2) Select a time interval for calibration (substract sinusoidal wawe at spin frequency via a ‘desinus’ software ; requires the knowledge of the spin frequency) (Selecting this time interval is required to apply FFT and calibrate ) (FFT, Correction of tranfer function by *1/G(fi) ; cut-off at low frequency ) 5) Get calibrated time series data in nT, in the spinning Sensor Coordinate System (SCS) 6) Waveform transformation from SCS to Despun System (Require Spin phase) (FFT -1) 7) Waveform transformation from SCS to GSE System, or others (GSM, MAG, GEO…) (Require Rocotlib software or other) Single Calibration In sensor coordinates Change to Despun or other classical coordinate systems

SWGTemplate- 6 UCB, Nov 15/16, 2006 SCM calibration processing (II) Making use of calibration method (Steps 1-5)

SWGTemplate- 7 UCB, Nov 15/16, 2006 Physical quantities (L2 data): In DSC (Despun System Coord.), GSM and GSE coordinates FS waveforms (scf) of Bx, By, Bz [8 S/s; All.~ 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)

SWGTemplate- 8 UCB, Nov 15/16, 2006 L2 subset: Magnetic field aligned frame (MFA) Mininum variance frame (MVA) Polarisation analysis Using FFT and assuming .  B =0 and k   we can get the k direction and large and small ellipse axis directions k SCM science data (II) z B0B0 kk kk  

SWGTemplate- 9 UCB, Nov 15/16, 2006 Commissioning: SCM should be turned on at the beginning in order to measure the noise generated by each instrument SCM should be turned on with an operation mode allowing a good characterization of generated noise for instance with waveform at 256 S/s or may be short period at max. sample rate (16384 S/s) SCM comments