Testing high-precision electromechanical actuators used for adjustment of deployable antennas of astronomy space missions

•High-precision electromechanical actuator for space applications has been designed.•Actuator for operation in vacuum under cryogenic temperatures (~4K) has been tested and studied.•Actuator’s thermal impact on the cryogenic main Mirror of Millimetron observatory (Spektr-M space mission) have been evaluated.•Mathematical model of the thermal interaction between the actuators and the petals of the main mirror have been presented. Actuators for deployable space antennas operating under temperatures around the liquid helium point (~4.2 K) are in great demand since the number of space missions involving deployable mirrors is growing. We are suggesting a design of actuators to provide adjustment of mirrors with the active surface control system having in view the Millimetron observatory (Spektr-M space mission). Having defined the reference precision, power consumption, and resistance to vacuum and cryogenic temperatures of such actuators, we have analyzed probable solutions, and accordingly created our own cryogenic models based on a well-proven motor previously used for similar but non-cryogenic applications. We are suggesting that these models could be used as the developmental prototypes for batch production thus cutting possible costs. The cryogenic tests of our developmental prototypes have been conducted both in the boiling liquid nitrogen medium and under closest to open space conditions in the cryogenic vacuum chamber with the Cryomech closed-cycle cryorefrigerator PT-407 cooled down to the liquid helium point. The original test setups which were a challenge in itself, test algorithms, and the test results are being presented. The properties and electrical characteristics, and results of the tests of the actuators’ thermal behavior when adjusting a deployable mirror in emulated real-life situations mimicking the conditions of the Millimetron observatory are being discussed.