Odysseus, Intuitive Machines’ first lander, landed on the moon in February 2024. But not perfectly.
The spacecraft was almost doomed before it even left Earth. Safety switches on laser instruments to measure the spacecraft’s altitude were still enabled, making them unusable. Mission controllers did not realize that error until Odysseus was in orbit around the moon, 200,000 miles away, and there was no way to fix the problem.
Odysseus was also carrying an experimental instrument called the Navigation Doppler Lidar, which NASA wanted to test — essentially a more sophisticated instrument with three laser beams that measure not just altitude but the velocity of the spacecraft during its descent.
Engineers at Intuitive Machines hurriedly patched Odysseus’ software to substitute the NASA instrument. They got that done in time — except they forgot to update one parameter in the computer code, and the navigation software ignored the altitude data.
Amazingly, Odysseus was still able to land using just estimates of the altitude, but the estimates were not perfect.
When it touched the ground, the lander was descending faster than expected and still moving sideways at two miles per hour, when the motion should have been perfectly vertical. As a result, the spacecraft toppled.
Odysseus continued to operate and was able to communicate with mission control at Intuitive Machines. That meant it was counted as a successful landing. But in the toppled orientation, Odysseus was not able to conduct much of the scientific work it had been sent to do.
By coincidence, a lunar lander sent by JAXA, the Japanese space agency, had also tipped over a month earlier. In that case, a nozzle on one of the lander’s main engines fell off, and the spacecraft was not able to fully compensate.
