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Spectrum analyzer allows onboard computation of electromagnetic waves spectra registered (observed) in the ionosphere and magnetosphere in the ELF/VLF frequency band. There are for example events connected with whistler mode wave propagation and their interaction with particles as well as other phenomena in this frequency band. Wave analysis together with particle measurements represents an important complement to the measurement of cold plasma parameters.
The instrument analyses spectrum of a magnetic field component. It consists of magnetic antenna, preamplifier, 16 bit sigma delta AD converter, DSP processor and telemetry interface. The DSP processor performs 1024 point FFT algorithm. The spectral lines are then logarithmically compressed into the chosen number of spectral bandwidths - channels (48/64/96/128), so the ratio channel bandwidth / frequency remains almost constant. The channels of lower frequencies are averaged and transmitted with lower repetition rate so the telemetry volume is reduced.
The instrument is mechanically divided into two blocks. One block is the magnetic antenna with preamplifier and AD converter, the other one is the CPU with DSP processor, telemetry interface and power supply.
Magnetic antenna with preamplifier and ADC:
Sensitivity: 6 ×10E-6 nT/(Hz)^-1/2
Frequency range: 200 - 20000Hz
Size: 204 x 103 x 60 mm
Mass: 0.3 kg
Can be modified for other frequency range, the mass and sizes would be in that case a little bit different.
Placement: Magnetic antenna with preamplifier has to be placed as far from the satellite (respectively from the artificial sources emitting electromagnetic noise) as possible.
Block CPU:
Size: 200 x 150 x 30 mm
Mass: 0.75 kg
Placement: There are no special requirements to the placement of the CPU block, but we would prefer to place it inside the satellite.
Main characteristics of the analyzer:
Frequency range: 200 - 20000Hz
Dynamic range: 90 dB
Sensitivity: 6 10E-6 nT/(Hz)^-1/2
Sampling rate: 48kHz (see note)
Time resolution: 20 ms
Frequency resolution: depends on the chosen number of channels
(50 Hz at 200 Hz, 420 Hz at 20 kHz for 128 channels)
Required telemetry rate: min 32 kbit/s
Power supply: < 1 W
Telemetry and command interface: RS485, can be tailored according to the requirements
Note:
1. The analyzer can be modified for more magnetic fields components, e.g. as three component analyzer. If these should be processes parallel the required telemetry volume and power consumption has to be tripled.
2. The analyzer can be used for different spectral range up to 50 kHz if equipped with another sensor. It can analyze also very low frequencies, e.g. 0,01 - 1 Hz, it depends on the chosen sampling rate. The required telemetry volume depends on the chosen sampling rate.
Institute of Atmospheric Physics, Prague, Czech Republic
The persons responsible for scientific interpretation are
Frantisek Jiricek, E-mail: fji@ufa.cas.cz, fax +420 2 71762528, tel.: +420 2 67103057 and
Vladimir Truhlik, E-mail: vtr@ufa.cas.cz, fax +420 2 71762528, tel.: +420 2 67103058
The persons responsible for technical solution are
Jaroslav Vojta, E-mail: jvo@ufa.cas.cz, fax +420 2 71762528, tel. : +420 2 67103303 and
Jaroslav Chum, E-mail: jch@ufa.cas.cz, fax +420 2 71762528, tel.: +420 2 67103303