MVN experiment – All sky monitor for measuring cosmic X-ray background of the universe onboard the ISS

The article describes the MVN experiment (MVN – Monitor Vsego Neba in Russian transliteration) – All Sky Monitor onboard the ISS, which will start in 2021. The main scientific task of the experiment is to measure the cosmic X-ray background in energy range of 6 – 70 keV with unprecedented high absolute and spectral accuracy (about 1%). To reach this goal, Space Research Institute of the Russian Academy of Sciences has developed scientific payload called MVN. The main instrument of MVN is the SPIN-X1-MVN X-ray monitor, which is equipped with four CdTe based semiconductor detectors. The X-ray monitor will be mounted on the external surface of the ISS with zenith orientation. The structure of the monitor including the key systems (detectors, gears, thermal control system) is considered. Measuring of the cosmic X-ray background is carried out by the aperture modulation method described in detail in this article. Also we describe an optimal algorithm of the obtained in experiment data filtering, which will provide us with highest quality of the CXB measurement.