Mars Express deploys second radar boom

 作者:桓绚蜡     |      日期:2019-02-27 02:18:02
By Maggie McKee The second of two identical radar booms has been deployed on Europe’s Mars Express spacecraft – but it is not yet clear if the operation was successful. If it was, the antenna could begin scouting for underground water on Mars within a week. Mission managers in Darmstadt, Germany, deployed the 20-metre-long boom on 14 June at 1130 GMT. After a series of manoeuvres designed to warm the boom evenly in sunshine, the spacecraft reoriented itself towards Earth about two hours later and began beaming data to mission control. “It’s always good to see your spacecraft back under control,” says Fred Jansen, the spacecraft’s mission manager. “But we know from the first boom’s deployment that this does not tell the full story, so we are not declaring the operation successful yet.” That first boom in the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) experiment popped out of its storage box on 4 May. But a few days later, engineers discovered one of its outer hinges had failed to lock into place during deployment, leaving a slight kink in the antenna. Mission managers suspected the coldness of space played a role in the problem, so on 10 May they exposed the crooked boom to the Sun for a few minutes. The warming trick worked – the boom straightened and locked in place – but an analysis showed the spacecraft itself could become unstable if a kink were to occur on an inner segment of the second boom. So mission planners postponed the deployment of that boom – which is crucial for the instrument to function – to study the issue. In deploying boom 2, mission managers set Mars Express rotating very slowly with the stored boom facing generally towards the Sun. Then, they deployed the boom and kept rotating the spacecraft so that, in half an hour, the boom rotated through 180 degrees. “So if you assume a hinge is at an angle somewhere, the Sun would illuminate all the hinges and heat them up,” Jansen told New Scientist. Managers will study data from the spacecraft’s gyroscopes, which measure its rotation, to see whether the boom deployed straight. They hope to finish their analysis of the deployment on Thursday. If the procedure was a success, mission officials will deploy the third and final boom on 17 June. This is a 7-metre-long pole that will help determine whether the reflected radio waves are coming from underground, but it is not critical to the mission. If all goes to plan, the experiment is set to record its first data on 21 June,