DEVELOPMENT OF A HIGH TEMPERATURE ANTENNA POINTING MECHANISMS FOR BEPICOLOMBO PLANETARY ORBITER

摘要

BepiColombo is an ESA mission to Mercury its planetary orbiter (MPO) has two antenna pointing mechanism, High gain antenna pointing mechanism steers and points a large reflector which is integrated at system level by TAS-I Rome. Medium gain antenna (MGA) APM points a 1.5 m boom with a horn antenna. Both radiating elements exposed to sun fluxes as high as 10 solar constants without protections. The pointing mechanism is a major challenge as high performances are required in a harsh environment. It has required the development of new technologies, and components specially dedicated for the mission needs. Some of the state of the art required for the mission was achieved during the preparatory technology development activities [1]. However the number of critical elements involved, and the difficulties of some areas have required the continuation of the developments, and new research activities had to be launched in CD phase. Some of the major concerns and related areas of development are: 1 High temperature and long life requirements for the gearhead motors (up to 15500 equivalent APM revolutions, 19 million motor revolution) 2 Low thermal distortion of the mechanical chain, being at the same time insulating from external environment and interfaces (55 arcsec pointing error) 3 Low heat leak to the spacecraft (in the order of 50W per APM) 4 High precision position control, low microvibration noise and error stability in motion (16 arcsec/s) 5 High power radio frequency (18W in band Ka, 30 in X band) with phase stability for use in radio-science (3mm in Ka band, 5o in X band). 6 Wide range of motion (full 360o with end-stops) Currently HGA APM EQM azimuth and elevation stages are assembled and ready for test at actuator level.