ART-XC/SRG: results of qualification thermo-vacuum tests

ART-XC - a medium-x-ray-energy survey instrument of "Spectrum-Roentgen-Gamma" (SRG) project is being developed in Russia under the leadership of the Space Research Institute (IKI). Main requirements to the telescope temperature control system are provided by two key elements - module of seven semiconductor DSSD CdTe detectors which have to operate at the temperature -22.5+/-2.5 °C to prevent CdTe crystals fast polarization (large polarization time allows to keep detector energy spectral characteristics during continuous 2 - 3 days expositions) and the module of seven mirror systems which have to operate at a temperature 20+/-2 °C (which is the temperature used in the on Earth mirror systems calibration tests).Thermal control system ART-XC consists of 36 tunable film heaters placed in different places on the telescope structure and controlled according to indications of thermal sensors. The maximum power of each heater is 10 W. There are 21 heaters located on seven mirror systems. Each mirror system case is equipped with two heaters, additional one is located on the mirror system baffle. Seven heaters are placed on detectors. Remaining eight heaters are placed in different telescope parts - one on the protective cover, one on the explosive pin, one under the star tracker, three on the mirror system and star tracker mount plate, one on the detector block mount plate and one on the calibration sources control system block. Thermal control system constantly checks temperature from 36 thermal sensors and regulate the heater's power supply. There is one passive thermal control element in the telescope - radiator, which is connected to detectors via three heat pipes and cools them down. The QM (qualification model) of ART-XC was manufacture and tested. QM completely corresponds to flight model. Conditions of thermo-vacuum tests were corresponded to real external thermal conditions in flight. The vacuum, cold of space, temperature of mounting planes and shielding by eRosita telescope were reproduced at this test. During the test operating and calibration thermal telescope modes were simulated. Results of the QM thermo-vacuum test are presented in this paper.