By Kenneth Chang
Soon it will be time to say, “Good night, moon lander.”
On Feb. 22, Odysseus, a privately built robotic lunar lander, became the first U.S. spacecraft to set down on the moon in more than 50 years, and the first nongovernmental effort ever to accomplish that feat.
But like the Homeric Greek hero it was named after, the lander has not had an easy journey with a neat, happy ending. The spacecraft encountered a series of near-calamitous challenges, almost lost its way, then landed crookedly.
During a news conference, Intuitive Machines, the Houston-based company that built Odysseus, said the spacecraft continued to operate, but that it would be put into a planned shutdown within a few hours.
Despite everything that did not work quite right, Steve Altemus, the chief executive of Intuitive Machines, called the mission “an unqualified success.”
Odysseus achieved its main objective, Altemus said, which was “to touch down softly on the surface of the moon, softly and safely, and return scientific data to our customers.”
Engineers toiled over the weekend, trying to speed up the communications with Odysseus and retrieve data.
The timeline for how long the mission might last shifted several times.
Originally, it was to last nine or 10 days, until the sun set on the solar-powered spacecraft. But with Odysseus lying at an angle, its solar panels were not in the ideal orientation to collect sunlight and generate power.
The company suggested earlier this week that dwindling power might end lander operations on Tuesday. Then, on Tuesday, it said the vehicle could hang on for as long as 20 additional hours. Wednesday’s announcement added a few more.
“Odie will sleep after that,” Altemus said, using the lander’s nickname.
On Wednesday, the story of how Odysseus got to the ground without crashing into pieces became even more incredible.
Intuitive Machines had already disclosed that the laser instrument on Odysseus for measuring its altitude during descent was not working. Safety mechanisms to prevent the lasers from firing accidentally on Earth had never been removed.
In the hours before landing, engineers hurriedly rewrote guidance software on Odysseus to use altitude readings from a more advanced but still experimental laser device that NASA was testing on this flight.
But the programmers overlooked one spot in the software that needed to be updated, and the spacecraft’s computer ignored the altitude data. Thus, during the landing descent, Odysseus did not know precisely how high above the moon’s surface it was. However, it was able to make guesses of its altitude based on its horizontal speed calculated from camera images and measurements of accelerations in the spacecraft’s velocity.
“It’s the first time anybody’s flown this algorithm, and it exceeded expectations, because we lived to tell about it,” Altemus said.
Last Thursday, it was not immediately evident that Odysseus had arrived in working order.
For several anxious minutes after the time of landing passed, flight controllers at Intuitive Machines waited for a radio signal from the lander to confirm that it had reached its destination in the moon’s south pole region. When the signal was detected, it was faint, indicating that the spacecraft’s antennas were pointing away from Earth.
The next day, Intuitive Machines officials disclosed that Odysseus had toppled over after hitting the ground harder than planned. Instead of making a perfectly vertical landing, Odysseus had still been moving sideways as it touched down.
Altemus showed a photograph taken at the moment of landing.
“This is a picture of Odie on the surface of the moon, touching down with its engine firing,” he said. “You see here, the landing gear, pieces broken off there on the left of the image.”
Intuitive Machines was never able to fully overcome the communications slowdown caused by the misdirected antennas, and NASA, which paid Intuitive Machines $118 million to take six instruments to the surface of the moon, did not gather as much scientific data as it had hoped. But the mission was not a total loss.
Tim Crain, the chief technology officer at Intuitive Machines, said Odysseus had sent back 350 megabytes of science and engineering data.
Crain also described other glitches suffered by Odysseus, including a startracker that initially failed to track stars and an engine that appeared to be unbalanced, as well as arriving at the moon in the wrong orbit. Each time, Intuitive Machines engineers found workarounds.
For NASA, the partial success provided some validation for its strategy of relying on entrepreneurial companies to deliver its instruments, rather than building and operating the spacecraft itself.
“We now have that evidence” that such missions can work, said Joel Kearns, the deputy associate administrator for exploration in NASA’s science mission directorate.
Odysseus might wake up in a few weeks when the sun rises again. Crain said it was likely the solar panels would still be able to generate power, but the rest of Odysseus may not make it through the two weeks of lunar night when temperatures drop to about minus 250 degrees Fahrenheit.
“The No. 1 limiter we face is the batteries,” Crain said. “That chemistry does not respond well to deep cold.”
The batteries, computer and radios on Odysseus were not tested to determine if they would still work after a long chill.
But they might. A Japanese lunar lander, also solar-powered, revived over the weekend after it made it through lunar night.