Inside a small control room, during the middle of the day on Thursday local time in Texas, about a dozen white-knuckled engineers at a space startup named Intuitive Machines started to get worried. Their spacecraft, a lander named Athena, was beginning its final descent down to the lunar surface.
A little more than a year had passed since the company’s first attempt to land on the Moon with a similarly built vehicle, Odysseus. Due to problems with that spacecraft’s laser rangefinder, it skidded into the Moon’s surface and toppled over.
So engineers at Intuitive Machines had checked, and re-checked the laser-based altimeters on Athena. When the lander got down within about 30 km of the lunar surface, they tested the rangefinders again. Worryingly, there was some noise in the readings as the laser bounced off the Moon. However, the engineers had reason to believe that, maybe, the readings would improve as the spacecraft got nearer to the surface.
“Our hope was that the signal to noise would improve as we got closer to the Moon,” said Tim Crain, chief technology officer for Intuitive Machines, speaking to reporters afterward.
It didn’t. The noise remained. And so, to some extent, Athena went down to the Moon blind. The spacecraft’s propulsion system, based on liquid oxygen and methane, and designed in-house, worked beautifully. But in the final moments, the spacecraft did not quite know where it was relative to the surface.
Probably lying on its side
Beyond that, Crain and the rest of the company, including its chief executive Steve Altemus, could not precisely say what happened. After Athena landed, the engineers in mission control could talk to the spacecraft, and they were able to generate some power from its solar arrays. But precisely where it was, or how it lay on the ground, they could not say a few hours later.
Based on a reading from an inertial measurement unit inside the vehicle, most likely Athena is lying on its side. This is the same fate Odysseus met last year, when it skidded into the Moon, broke a leg, and toppled over.
