‘OUR EQUIPMENT IS ON THE SURFACE OF THE MOON’
Tense scramble to switch out landing sensors
The spacecraft had travelled from Earth to the moon, hitting the precise spot where lunar gravity would seize it and put it in a stable orbit. Now, some 92 kilometres above the surface, the spacecraft was close enough to send back photos of the moonscape below, grey and desolate, with craters and hills casting long shadows and revealing a treacherous lunar topography for what would become a historic landing Thursday evening.
In the end, the mission was heralded as a success — the first American moon landing since Apollo 17 in 1972.
But the descent to the surface was a perilous nailbiter that required on-thefly ingenuity to save it from failure. And it served as a reminder that space travel remains an extraordinarily risky endeavour and that the moon, even 50 years after the United States first landed astronauts there, remains a forbidding and elusive target.
On Friday, Intuitive Machines, the firm that designed and operates the lander, said the vehicle was “alive and well” and that “flight controllers are communicating and commanding the vehicle to download science data. The lander has good telemetry and solar charging.”
But that was not certain on Thursday afternoon as the spacecraft was to begin its descent. That’s when ground controllers realized they had a big problem: The sensors on board their Odysseus spacecraft were not working. Without them, the spacecraft was essentially flying blind. If Odysseus were to touch down softly, Intuitive Machines would have to fix this — and fast.
Ground controllers, searching to fix the problem, needed more time. So they commanded the 14-foot-tall spacecraft, which looks like a phone booth on stilts, to orbit the moon once more.
NASA had known that its decision to send a fleet of privately developed robotic spacecraft to the moon was a risk. The Commercial Lunar Payload Services program (CLPS) is unlike any deepspace program NASA had ever done. NASA would not own or operate the craft.
Intuitive Machines was working under a US$118 million contract from NASA as part of the program. Last month, the agency’s first CLPS mission, carried out by Astrobotic, suffered a propulsion problem, lost fuel and did not reach the moon. Now, it seemed Intuitive Machines might not make it, either.
The sensors Odysseus intended to use to find a landing site were out. But ground controllers knew they had a backup: a 33-pound instrument developed by NASA affixed to the outside of the spacecraft like a large barnacle on the hull of a ship.
The system was not meant to be used to guide the spacecraft to landing; rather, it was on board as an experiment. Called the Navigation Doppler Lidar (NDL), it would use lasers to calculate velocity and distance to the surface during the descent. It works like the radar detector police use to nab speeders, but uses “pulses of light from a laser instead of radio waves and with very high accuracy,” Intuitive Machines explained before the mission.
While Odysseus remained in lunar orbit, ground controllers scrambled to develop a software patch to transmit to the vehicle, directing it to feed the readings from the NDL system into the spacecraft’s computer, instead of using the primary system.
Josh Marshall, Intuitive Machines’ director of communications, described a “dynamic situation” swapping out the sensors on the fly, with the spacecraft some 240,000 miles from Earth.
The landing was tense. The spacecraft fired its engine for 11 minutes, throttling back as the vehicle burned through fuel and got lighter and lighter. The landing time, 6:24 p.m. came and went without confirmation of landing. It was unclear whether the spacecraft had survived, or what condition it was in.
About two minutes after the intended landing time, mission director Tim Crain called out to his team: “Please look back through your logs and confirm the last information you had, and we’ll determine if this is a comms outage.”
A few minutes later, Crain polled his team again. “Looks like we had excellent pitch and yaw control throughout,” he said, referring to the orientation of the spacecraft during the descent. “But it did see a little bit of a roll excursion. Could it be that we landed off-angle in the final phase?”
Maybe the spacecraft had landed and tumbled? As the teams tried to find out, they also scrambled to re-establish communications.
Finally, about 10 minutes after the intended landing time, Crain had good news: “Signs of life,” he said. “We have a signal we’re tracking.”
The signal, he said, was “faint, but it’s there.”
A minute later: “What we can confirm without a doubt is our equipment is on the surface of the moon. And we are transmitting. So congratulations, IM team.”
The room broke into applause.