It turns out that Odysseus landed on the Moon without any altimetry dataars TECHNICA by Eric Berger - 2/27/2024
"Hours after we got off the launch pad, we almost lost the spacecraft."HOUSTON—Steve Altemus beamed with pride on Tuesday morning as he led me into Mission Control for the Odysseus lander, which is currently operating on the Moon and returning valuable scientific data to Earth. A team of about a dozen operators sat behind consoles, attempting to reset a visual processing unit onboard the lunar lander, one of their last, best chances to deploy a small camera that would snap a photo of Odysseus in action.
"I just wanted you to see the team," he said.
The founder and chief executive of Intuitive Machines, which for a few days this month has been the epicenter of the spaceflight universe after landing the first commercial vehicle on the Moon, invited me to the company's nerve center in Houston to set some things straight.
"You can say whatever you want to say," Altemus said. "But from my perspective, this is an absolute success of a mission. Holy crap. The things that you go through to fly to the Moon. The learning, just every step of the way, is tremendous."
Altemus will participate in a news conference on Wednesday at Johnson Space Center to provide a fuller perspective of the journey of Odysseus to the Moon and all those learnings. But I got the sense he invited me to the company's offices Tuesday because he was itching to tell someone—to tell the world—that although Odysseus had toppled over after touching down, the mission was, in his words, an absolute success.
After more than an hour of speaking with Altemus, I believe him.
Odysseus is a beastly machine, and the team flying it isn't shabby, either. They have certainly busted their asses. The offices in south Houston were littered with the remains of junk food, coffee, and other elixirs of long nights and wracked brains. It's all been a whirlwind, no doubt. Next to a bag of tortilla chips, there was a bottle of Ibuprofen.
Coming in blindAs has been previously reported, Intuitive Machines discovered that the range finders on Odysseus were inoperable a couple of hours before it was due to attempt to land on the Moon last Thursday. This was later revealed to be due to the failure to install a pencil-sized pin and a wire harness that enabled the laser to be turned on and off. As a result, the company scrambled to rewrite its software to take advantage of three telescopes on a NASA payload, the Navigation Doppler Lidar for Precise Velocity and Range Sensing, for altimetry purposes.
While this software patch mostly worked, Altemus said Tuesday that the flight computer onboard Odysseus was unable to process data from the NASA payload in real time. Therefore, the last accurate altitude reading the lander received came when it was 15 kilometers above the lunar surface—and still more than 12 minutes from touchdown.
That left the spacecraft, which was flying autonomously, to rely on its optical navigation cameras. By comparing imagery data frame by frame, the flight computer could determine how fast it was moving relative to the lunar surface. Knowing its initial velocity and altitude prior to initiating powered descent and using data from the inertial measurement unit (IMU) on board Odysseus, it could get a rough idea of altitude. But that only went so far.
"So we're coming down to our landing site with no altimeter," Altemus said.
Unfortunately, as it neared the lunar surface, the lander believed it was about 100 meters higher relative to the Moon than it actually was. So instead of touching down with a vertical velocity of just 1 meter per second and no lateral movement, Odysseus was coming down three times faster and with a lateral speed of 2 meters per second.
More:
https://arstechnica.com/space/2024/02/it-turns-out-that-odysseus-landed-on-the-moon-without-any-altimetry-data/
