WASHINGTON — Astrobotic confirmed Jan. 17 that its Peregrine lunar lander will reenter over the South Pacific on Jan. 18, concluding a 10-day mission that failed to land on the moon because of a propellant leak.
In a statement, the company said it had adjusted the spacecraft’s trajectory to ensure it would safely reenter at about 4 p.m. Eastern Jan. 18. The reentry location in an ellipse several hundred kilometers long with its center a little more than 500 kilometers south-southwest of Fiji.
The company said it had to perform a two-step process to put the spacecraft on that reentry trajectory. One involved a series of 23 short burns by the spacecraft’s main engines. Astrobotic first tested those main engines Jan. 13, confirming they worked. However, the company said at the time that, because of the oxidizer leak, the fuel-to-oxidizer ratio “is well outside of the normal operating range of the main engines making long controlled burns impossible.”
Astrobotic said it also oriented the spacecraft so that the force from the leaking propellant would push the spacecraft towards the desired reentry zone over the South Pacific, ensuring that any debris that survives reentry will fall outside of populated regions.
The company announced Jan. 13 that the spacecraft appeared to be on a trajectory that would lead to reentry, and the next day said that, after discussions with NASA and others, it would allow the spacecraft to reenter rather than attempt a maneuver to miss the Earth. There had been speculation since then, though, that perturbations in the orbit caused by leaking fuel or other factors would require a maneuver to confirm a safe spacecraft reentry.
Peregrine launched Jan. 8 on the first United Launch Alliance Vulcan Centaur, but suffered a propellant leak hours later. The company said it believed a valve in a helium pressurization system failed to close, overpressurizing an oxidizer tank and rupturing it, creating the propellant leak.
The company was able to stabilize the spacecraft and turn on many of its payloads, even as it ruled out any attempt at a lunar landing because of the propellant leak. The launch placed Peregrine onto a highly elliptical orbit that took it out beyond the moon’s orbit. It was to swing back around the Earth before going into orbit around the moon to prepare for a Feb. 23 landing.
Peregrine carried 20 payloads, including five for its biggest customer, NASA’s Commercial Lunar Payload Services (CLPS) program. NASA said it backed Astrobotic’s decision to reenter the lander to safely conclude the mission.
“While it’s too soon to understand the root cause of the propulsion incident, NASA continues to support Astrobotic, and will assist in reviewing flight data, identifying the cause, and developing a plan forward for the company’s future CLPS and commercial flights,” Nicola Fox, NASA associate administrator for science, said in a Jan. 14 statement.
NASA and Peregrine plan to discuss the mission in a media briefing Jan. 19, hours after Japan’s SLIM spacecraft attempts its own landing on the moon.
