The Mission


Search Coil Magnetometer

The THEMIS Search Coil Magnetometer (SCM) measures low-frequency magnetic field fluctuations and waves in three directions. The search coil antennas cover the frequency bandwidth from 0.1 Hz to 4 kHz. They extend, with appropriate Noise Equivalent Magnetic Induction (NEMI) and sufficient overlap, the measurements of the fluxgate magnetometers (FGM). The NEMI of the search coil antennas and associated pre-amplifiers are not larger than 0.76pT/√Hz at 10 Hz, 0.08pT/√Hz at 100 Hz and 0.022pT/√Hz at 1kHz.

The analog signals produced by the search coils and associated preamplifiers are digitized and processed inside the Digital Field Box (DFB) and the Instrument Data Processing Unit (IDPU), together with data from the Electric Field Instrument (EFI).

Search coil telemetry includes waveform transmission, FFT processed data, and data from a filter bank. The search coils and their three axis structures have been precisely calibrated in a a calibration facility, and the calibration of the transfer function is checked on board, usually once per orbit. The tri-axial search coils implemented on the five THEMIS spacecraft are all working nominally.

Development Institution:
Centre d'étude des Environnements Terrestre et Planétaires (CETP), France
In January 2009, the SCM team will move to a new institution called Laboratoire de Physique des Plasmas (LPP)
SCM Leads
A. Roux and O. Le Contel
Search Coil Magnetometer


Detailed information on the THEMIS SCM instrument can be found in the following articles published in Space Science Reviews:


Would you like to see:

Principle of the Search Coil Measurement     Frequently Asked Questions
Caveats     Data Flow Diagram
More Pictures of the Search Coil Magnetometer        
Configuration History: Filter Bank (FBK)          Configuration History: Fourier Power Spectra (FFT)