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Induction magnetometer LEMI-606 for RESONANCE experiment

RESONANCE experiment focuses on the study of the processes in the inner magnetosphere of our planet. The objectives of the project include the investigation of interactions between waves and particles, and monitoring of the large-scale changes in the magnetosphere associated with geomagnetic activity and magnetic storms.

Magnetic field fluctuations will be measured by four tree-component induction coil magnetometers LEMI-606 which will installed on two pairs of satellites will be launched on a specially designed path - the so-called "magnetosynchronous orbits." It is known that the plasma parameters vary rapidly in space and time, so in the case of simultaneous measurements at four points high temporal resolution and low measurement error must be provided.

Because of that high demands on the possible identity of the parameters of devices that are on all four satellites are placed.

Three-component induction coil magnetometer LEMI-606 is intended for the study of magnetic field fluctuations in space conditions in the frequency band 1-20000 Hz. It is intended to be used as input sensor of Electromagnetic Wave Analyzer (ELMAVAN).


Each component of induction coil magnetometer LEMI-606 consists of induction coil sensor (ICS) and preamplifier, both located inside the same protective housing – black tube at the photo.

ICS consists of magnetic core, main winding and feedback winding.

The original peculiarity of the ICS magnetic core construction is that it is made of a number of longitudinal convex-shaped ferromagnetic high permeability amorphous tapes insulated one from another. In such a way the magnetic core forms a hollow tube that allows placing the preamplifier inside it. The main winding is wound on this core. This construction first, allows considerable weight decreasing and second, helps to protect additionally the preamplifier against the radiation what is especially important for RESONANCE experiment.

Output signal of main winding is coupled to ultra low-noise input preamplifier with local feed-back, the output of which is coupled to the magnetic flux feedback winding through the correction circuit. Magnetic and local feedback circuits form the flat part of the magnetometer transfer function within frequency band 100 – 20000 Hz; in the frequency band 1-100 Hz the output signal is proportional to the signal frequency.

There is also an additional high-frequency correction circuit inside preamplifier which serves to ensure the stable operation of all the system “ICS - preamplifier” in full frequency band. The counter-phase output signal to form the symmetric output for additional decreasing of interferences is provided by the output inverter.

The small box to which all three components of the induction magnetometer are fixed serves for the magnetometer fixation to the boom and contains power supply and communication boards. These units provide power voltage stabilization and transfer of magnetometer output signals to the ELMAVAN.

The main parameters of LEMI-606 are given below.


Full frequency band of received signal, Hz 1 … 20000
Flat part of transfer function in the pass band, Hz 100 … 20000
Transformation factor at flat part and at differential output, mV/nT 40
Magnetic noise level, pT×Hz^(-1/2):
at 1 Hz
at 100 Hz
at 1 kHz
at 10 kHz
Power supply voltage ± 5 V
Power consumption, mW 110
Outer dimensions (one component), mm l = 360, d=30


The conditions of the magnetometer installation onboard the satellite platform constrain non-symmetric construction of the magnetometer. This imposes additional problem with mutual influence of the components and their orthogonality. Because of this the calibration of the LEMI-606 must be executed in the assembled structure only, what creates serious problems to find the convenient calibration facility. Between all known ones it seems that the Calibration stand at Garchy, France, is the only place where the parameters of this magnetometer may be checked in all operation frequency range. These tests were made with flight model and showed satisfactory parameters.

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Last modified: 10-11-2015

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