The reliability of both spacecraft as a whole and of their systems is confirmed at the stage of complex ground-based experimental tests, including complex thermal vacuum tests. The thermal state of the test object in thermal vacuum chambers is obtaining, in particular, using a solar simulator. Radiometers based on silicon photoelectric converters are most often used to control the irradiance of a solar simulator under conditions of thermal vacuum tests. At the same time, an analysis of the features of silicon photoelectric converters shows that their direct measurement with the accuracy required for ground-based tests of spacecraft is impossible; their output is nonlinear, depends on the received spectrum, their own temperature and has long-term instability. The achieved measurement accuracy directly depends on the number and accuracy of the tools used and the methods of the necessary correction, of which the mismatch correction between the solar simulator spectrum and the solar spectrum is the most difficult and laborious. At the same time, spectrally nonselective heat flux radiometers are free from the above disadvantages. In the course of the experiment we carried out, the significant dependence of the accuracy of measuring the irradiance with radiometers based on silicon photoelectric converters on the received spectrum was confirmed. The conclusion is made that direct measurement by heat flux radiometers of the irradiance of the solar simulator is most justified under the conditions of thermal vacuum tests.

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Many new thermal vacuum testing programs for ground testing of spacecraft require ensuring high accuracy temperature regime in a wide temperature range. Thermal vacuum tests are notable for significant material costs. Therefore, the requirement to reduce operating costs, including those associated with ensuring the temperature regime, is not less relevant. This explains the increased interest in promising energy-efficient technologies, one of which is based on the thermal conditioning of gaseous nitrogen. Systems with gaseous nitrogen thermal conditioning units have an optimal combination of operational and technical characteristics and, compared to systems where liquid nitrogen is poured into cryogenic screens, have lower consumption of liquid nitrogen and electrical energy, especially in stabilized temperature regime. The risk of contamination of the thermal vacuum chamber and the test object due to leaks of the liquid coolant is eliminated. Due to the fact that the properties of nitrogen quite accurately correspond to the ideal gas law, modeling of such systems is relatively simple, and the characteristics are predictable and stable. The article provides a brief analysis of the characteristics of gaseous nitrogen thermal conditioning units of two leading foreign manufacturers and the results of the practical application of four foreign manufactured thermal conditioning units with different characteristics in a typical thermal vacuum chamber. We considered the main directions of improving the characteristics of thermal conditioning units by foreign manufacturers. The conclusion is made about the high efficiency and economic feasibility of gaseous nitrogen thermal conditioning technology in most cases of thermal vacuum testing.

Создание в СССР и России информационных космических систем и комплексов прикладного назначения послужило обеспечению миллионов наземных потребителей всеми видам связи и иных информационных услуг, удовлетворению потребностей страны в областях как её обороноспособности, так и комплексного социально-эко-

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