Mark Megahan
The engineers in charge of NASA’s CAPSTONE satellite program can breathe again. Those sleepless nights staring at the ceiling in horror paid off when they regained control of their crucial project. They still don’t have it fixed but know what the problem is and can cope with it using workarounds.
CAPSTONE back under control
Engineers are thrilled to announce that they have “restored normal attitude control” of their CAPSTONE cubesat. They’ve been frantically working on the problem for a month.
The last time they did an orbit correction maneuver, something went wrong, sending a crucial part of the Artemis Moon project tumbling totally out of control. To save its life, they put it in a coma to let the batteries charge.
According to an October 7 statement from Advanced Space, owner of the Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment, they were “able to restore normal three-axis attitude control of the spacecraft earlier that day.”
Proving that slow and steady pays off, the CAPSTONE mission has pulled a rabbit out of their hat and restored the spacecraft to nominal operations. Congratulations for a job well done! https://t.co/Li5gvYD7O4
— Richard Stephenson (@nascom1) October 7, 2022
CAPSTONE “had been in a spin-stabilized state since going into a safe mode during a trajectory correction maneuver September 8.”
They managed to track the issue down to a stuck valve on one of the eight thrusters. The issue is similar to a leaky faucet. CAPSTONE engineers report the “partially open valve resulted in thrust from the associated thruster whenever the propulsion system was pressurized.”
That makes a huge difference in microgravity. They spent the last month in brainstorming sessions, extensive testing and simulation.
Restore normal control
Once they got their head around what was happening, CAPSTONE controllers “uploaded commands to the spacecraft October 6 to restore normal three-axis attitude control.” A basic software patch did the trick to stop the spin.
“Initial telemetry and observation data after the recovery attempt points to a successful recovery of the system which has now regained 3-axis attitude control.” The valve is still stuck though.
The engineers can finally breathe normally but are still keeping their fingers crossed.
As Advanced Space notes, “assuming the spacecraft remains in its normal attitude, it will work on changes to other spacecraft procedures for subsequent maneuvers that incorporate the effects of the partially open valve.” This is the second little problem for the CAPSTONE mission since launched last June.
Right after it got pushed loose from Rocket Lab’s Lunar Photon kick stage on the fourth of July, “the spacecraft lost contact with controllers.” They manged to get the satellite back on the phone the next day, blaming that one on “a series of events that included an improperly formatted command.”
You don’t have to be an engineer working on CAPSTONE to know how common coding mistakes like using a single wrong space can cause terrible nightmares later. These sorts of glitches never seem to surface in testing, only when it matters.
