Deployable boom for Mars Orbiter Magnetometer onboard Tianwen-1

A more than 3 m-long deployable boom is an essential component of the Mars Orbiter Magnetometer (MOMAG) onboard the orbiter of Tianwen-1. The boom was developed to place fluxgate magnetometer (FGM) sensors away from the satellite to reduce the influence of the satellite magnetic field. It was designed as an articulated spring-driven deployable mechanism for single-shot deployment. Functionality, reliability and system constraints are fully considered in the boom design. Mechanical analyses and proof tests show that the boom has sufficient safety margin to withstand environmental conditions, even in the worst cases. After a long voyage from Earth to Mars, the boom was deployed successfully on May 25, 2021. A full deployment was performed in about 4.6 s, sending the two sensors to distances of 3.19 m and 2.29 m respectively, away from the orbiter. After deployment, the field from the orbiter decreased from 1250 nT to less than 6 nT at the sensor mounted at the tip of the boom. The MOMAG boom provides valuable engineering experience for the development of deployable structures stowed for long periods in cold temperatures in space missions.