After a breakdown: NASA’s Capstone satellite swung into a special lunar orbit

Capstone is now orbiting the Moon in the same orbit as the proposed Gateway space station. This was preceded by a flight full of breakdowns.

Artist’s impression of Capstone on the moon (Image: Illustration by NASA/Daniel Rutter)

NASA’s Capstone probe has reached the moon after a mishap-filled flight. The probe entered a near-perpendicular halo orbit (NRHO) on Sunday, NASA said. The small satellite is now orbiting the moon in the same orbit as the planned Gateway space station. It should guarantee long-term stability and be able to be maintained with minimal energy consumption. Capstone is the first probe in this lunar orbit and also the first small CubeSat on the moon. The probe is currently still busy improving the orbit with further maneuvers, after which the evaluation of the collected data should begin, the US space agency said.

Capstone weighs 25 kilograms and is about the size of a microwave oven. Launched on June 28, the probe is a sort of signpost for the Gateway space station and the entire Artemis lunar program. On the way to the moon, she also tested an alternative, less fuel-intensive route that could be used by other unmanned moon missions in the future. However, the mission was not spared from problems. Due to an “improperly formatted command sequence”, NASA lost contact with the probe shortly after launch and not communicating with her for two days. Actually, the error detection system should have restarted the affected transmitter immediately, but this did not happen due to another error in the flight software. The software later fixed the problem.

In mid-September, NASA lost control of the “Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment” again, but after 24 hours without contact, at least a connection could be established again. In the meantime, it had become clear that, as a result of a maneuver, the probe had begun to wobble so severely that the onboard reaction wheels were no longer able to stabilize it. On October 7, the tumbling could be stopped with a corrective maneuver. According to NASA the risks for the probe were “significant” beforehand, and extensive work was needed to prepare for the maneuver. A valve is therefore faulty, it is now bypassed during further maneuvers. The probe has not been in safe mode since the end of October.


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