It turns out that Odysseus landed on the Moon without any altimetry data

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Written By Sedoso Feb

Odysseus lander is shown shortly before touching down on the Moon. “>
Enlarge / Intuitive Machines’ Odysseus lander is shown shortly before touching down on the Moon.
Intuitive Machines

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 blind

As 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.

“That little geometry made us hit a little harder than we wanted to,” he said.

But all was not lost. Based upon data downloaded from the spacecraft and imagery from NASA’s Lunar Reconnaissance Orbiter, which flew over the landing site, Intuitive Machines has determined that the lander came down to the surface and likely skidded. This force caused one of its six landing legs to snap. Then, for a couple of seconds, the lander stood upright before toppling over due to the failed leg.

The company has an incredible photo of this moment showing the lander upright, with the snapped leg and the engine still firing. Altemus plans to publicly release this photo Wednesday.

Completing the mission

Over the weekend, the company’s scientists and engineers raced to understand the condition of the lander. Yes, it was on its side. But one end appeared to be elevated. They realized this was due to a 12 percent slope of the terrain at the edge of a crater.

From a power standpoint, the engineering team received a blow, with the “top” of the lander now lying on the ground. A large solar panel on top of the vehicle was supposed to gather energy. It could still have helped had it been pointed toward the part of the horizon where the Sun was. However, due to the lander’s orientation, this end was pointed away from the Sun.

That meant all of the power coming into Odysseus was doing so through a single solar panel on its side, which was now facing upward. According to Altemus, this panel is producing about 170 watts of power. That’s more than enough to operate the lander but not simultaneously use the powerful Quasonix transmitter that sends broadband data back to satellite dishes on Earth. This requires 210 watts of power.

Odysseus, has solar panels on its sides as well as at the top of the vehicle.”>The Nova-C lander, named <em>Odysseus</em>, has solar panels on its sides as well as at the top of the vehicle.” src=”https://cdn.arstechnica.net/wp-content/uploads/2023/10/JT3A6259.jpg” width=”980″ height=”653″><figcaption class=
Enlarge / The Nova-C lander, named Odysseus, has solar panels on its sides as well as at the top of the vehicle.
Lee Hutchinson

The choice Intuitive Machines faced was whether to keep operating Odysseus for several more days on lower power as the Sun sank lower to the horizon or to use the juice when it had good line-of-sight communications with large satellite dishes back on Earth. That would mean losing most functions as soon as Wednesday.

“The question is, do you want to limp along and stay alive with everything shut off?” Altemus said. “Or do you want to go on the Quasonix, when you have the big ear listening, and get all the data you can? And that’s the decision we made, to go get all the data. It’s not how long you stay alive. It’s how much information you glean from this mission.”

The engineers were able to answer another mystery as well. They were getting communications from all four antennas on the lander, but two were sending back largely gibberish. It turns out that the muffled signal they were getting from those two antennas was bouncing off the surface of the Moon because the antennas were pointing downward. Mission operators were able to modulate the signal to get a clean stream of data.

As a result, the Intuitive Machines team expects to receive good data from five of the six NASA payloads on board. Only the Stereo Cameras for the Lunar Plume-Surface Studies experiment, intended to capture the effects of the lander’s engine plume as it interacted with the lunar surface, are not responding. Altemus said he believes this payload was damaged during the landing process. Most of the commercial payloads are working as intended.

Building a team

In thinking back over the 12 days since the Intuitive Machines lander launched on a Falcon 9 rocket, Altemus said the mission experienced 11 crises. The first of these happened shortly after the Falcon 9 rocket’s upper stage released the spacecraft into a translunar injection. The star trackers on board the spacecraft failed.

“We had no way to navigate in space,” Altemus said. “So we were gently rolling and tumbling through space. The battery was not charging. We could not orient the spacecraft. We were losing communication. Hours after we got off the launch pad, we almost lost the spacecraft.”

The mission operators were eventually able to regain communications with the lander and, after diagnosing the problem, managed to change a parameter that reset the star trackers. At the time, Odysseus was down to three hours of battery lifetime. Altemus said crises like this, and the loss of the range finders, happened over and over. “This mission kept throwing us alligators, and we would reduce these alligators to snapping turtles because they don’t hurt as bad,” he said.

If one assumes there is a 70 percent chance of recovering from any one of these crises but you have to address 11 different crises on the way to the Moon, the probability of mission success is less than 2 percent.

“The reason we made it is right here, our people,” he said. “The team we had, what they did, oh my God. They never quit. The perseverance, the resilience, just the power of the people we have in this team. That’s why we’re on the Moon.”

A success?

There are many ways to judge Odysseus. Some people heard the lander toppled over and assumed it was a failure. Others look at China or India having success with similarly sized landers on the Moon and see this as a failure of American ingenuity. The United States can’t even land a spacecraft on the Moon anymore?

But that’s an ignorant take. In truth, NASA is thrilled with Intuitive Machines’ performance. The aerospace industry at large understands what this company was up against and is celebrating its success. Most of the customers flying on Odysseus are getting the data they paid for.

The reality is that Intuitive Machines is a private company with about 250 people working on this lunar lander program. That’s a small fraction of the resources that national space programs typically devote to these initiatives, and with all the data it has gathered, Intuitive Machines and its customers can be pretty confident that the company will stick the landing next time.

And there will be a next time, as the commercial lunar landers built by private companies in the United States cost about $100 million instead of the half-billion dollars the government would have spent on a specialized, one-time mission to the Moon.

Here’s why I think this is a truly notable success. Consider the trials and turmoil that a similarly sized company called SpaceX went through 18 years ago as it worked toward the first launch of its first rocket, the Falcon 1. Rockets are hard, but so are spacecraft that must make a soft landing on the Moon. I would argue that a lunar lander like Odysseus is as complicated, if not more so, than a relatively simple booster like the Falcon 1.

That first Falcon 1 launch in 2006 failed. Its engine caught fire 30 seconds after liftoff, and pieces of the booster tumbled into the Pacific Ocean near the Kwajalein Atoll. A year later, the second launch failed due to a problem with the booster’s upper stage. Still, another year later, a third launch attempt failed. Here we are nearly two decades later, and SpaceX is the most accomplished rocket company in the world. It has built a highway to orbit. Intuitive Machines is trying to extend the expressway to the Moon.

Unlike the initial Falcon 1, Odysseus flew all the way to the Moon on its very first time out and made a soft landing. It has been phoning home ever since, sending a rich stream of data. That’s a pretty big win.

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