Аннотация:A multipurpose experiment with a number of instruments is being conducted on-board the "Mir-Spectr" orbital complex. Observations began on October 5, 1995. The main astrophysical instrument is a wide-field oriented scintillator spectrometer (similar to 300 cm(2) effective area, 10-300 keV energy range). It consists of 7 identical detector units with the axes turned 5 degrees to each other, which allows us to determine the direction on the source of the registered photons. The significant peculiarity of the experiment is the possibility of the continuous monitoring of gamma-quanta and relativistic electrons fluxes, which are responsible for those background components in the X-ray spectrometer, which can not be removed by instrumental methods. Due to the long exposure time and accurate background patrol, the X-ray timing of different galactic sources (including Sco X-1, Cyg X-1, Crab) as well as the registration of hard X-ray bursts (especially from the Soft Gamma-ray Repeaters) and transients are quite realistic in the experiment (the fluxes of weakest detectable bursts from SGR is less than or equal to 10(-8) erg/cm(2)). (C) 1998 COSPAR. Published by Elsevier Science Ltd.