Lenticular Jointed Antenna Deployment Anomaly and Resolution Onboard the Mars Express Spacecraft

During the summer of 2005, ESAdeployed a series of three lenticular jointed antenna booms that formed afirst-ofits-kind ground-penetrating radar antenna onboard the Mars Express spacecraft. The booms were each released from their cradles with a high level of stored energy and allowed to deploy in a chaotic manner with no direct control over their speed or range of motion until their final geometries were achieved. Despite careful preparations, an unforeseen anomaly occurred during the release of thefirst boom that resulted in apartially deployed state. Theflight team was able to determine the boom’s intermediate geometry with a high degree of accuracy and to recommend a corrective spacecraft maneuver. This determination, the measured boom properties, and the on-orbit environment that led to the irregularity are discussed, along with the subsequent resolution of the situation and the ultimately successful deployment. Experience gained from the first boom was used to develop a new spacecraft maneuver that was designed tomitigate the chances of another anomaly occurring during the deployment of the second boom,which took place successfully several weeks later. These activities are summarized and the resulting flight data are presented for both dipole booms, which demonstrate a fully deployed and healthy antenna.