NASA’s CAPSTONE Moon Probe Is Tumbling After Unknown Error

NASA is still working toward getting Artemis 1 off the ground, which is arguably the most important milestone in its quest to return humankind to the lunar surface. However, things are not going well with the first mission of the Artemis Program. The CAPSTONE probe, which launched in June aboard a Rocket Lab Electron rocket, is tumbling and partially disabled. It’s currently in safe mode, but it’s going to be a challenge to recover the spacecraft.

Everything seemed to be going by the book for the first few months of the mission. After an unremarkable launch, CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) completed the first two of six total course corrections in July. To reach its intended lunar orbit, CAPSTONE needs to loop out almost a million miles (1.53 million kilometers) from Earth before spiraling inward to the moon. It reached apogee (its furthest point) late last month, but things went wrong when the spacecraft executed its third maneuver on Sept. 8.

According to Advanced Space, which is managing CAPSTONE for NASA, the probe entered an uncontrolled tumble following the third maneuver, and the rate of spin exceeds what can be countered by the tiny spacecraft’s reaction wheels. NASA was unable to contact the probe for about 24 hours. After re-establishing communication, the team found the spin had left the solar panels unable to effectively charge the battery — it was using more power than it could generate, putting the fate of the mission in immediate peril. Luckily, the team was able to stabilize the spacecraft using the Deep Space Network, a collective term for the transmitters on NASA’s interplanetary missions.

CAPSTONE is just 25 pounds (11 kilograms), but it could have an outsized impact on NASA’s future lunar operations. Its goal is to test a newly proposed orbit around the moon known as near rectilinear halo orbit (NRHO). NASA hopes to eventually deploy the Gateway lunar station in this orbit, which would allow it to maintain continuous communication with Earth. No previous mission has utilized this lopsided course, which features an altitude of 47,000 miles (76,000 kilometers) at the north pole but at just 2,100 miles (3,400 km) when passing over the south pole.

Currently, CAPSTONE is still tumbling, but it’s in safe mode, and the solar panels are slowly but surely refilling the batteries. NASA has also confirmed that the cubesat completed its third course correction, meaning it is on track for another nudge in October. The success of that maneuver will depend on how the recovery team fares. First, they need to determine what caused the problem in the first place so it doesn’t happen again. Next, they’ll have to “detumble” the spacecraft so it can again communicate efficiently with Earth. However, NASA notes that there are still significant risks.