EMERGENCY POINTING ACTUATOR (EPA) RELEASE MECHANISM OF THE POINTING UNIT IN THE MERTIS BEPI COLOMBO EXPERIMENT

摘要

The paper presents Emergency Pointing Actuator (EPA) of the Pointing Unit (MPOI) as a part of the Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS) used in the Bepi Colombo mission. EPA shall be used in case of MPOI electronics failure. It can rotate the motor shaft with pointing mirror to the Mercury view position and keep this position all the time. The mechanism is based on a spiral spring which will be released on command. The reverse rotation of the spiral spring is blocked by a special fiber and it can be released by burning the fiber. The EPA mechanism was verified in different modes of operation and demanding environmental conditions. The tests included: thermal analysis for different modes, estimating time of fiber burning in variable temperatures.