It’s now been confirmed that the Athena lunar lander’s altimeter failed around the time the spacecraft reached the Moon. This instrument is key in the process of determining the lander’s distance from the surface, which it then uses during the final landing maneuver.
Without it, the Athena spacecraft didn’t know its distance from the ground, which no doubt had an impact on the lander tipping over and sliding into its final resting place in a crater.
Altimeter Failure
Athena’s laser altimeters use a 1.2-megawatt laser that fires for a few nanoseconds and has a range of 80km. The laser enables mission controllers to know the distance to the Moon’s surface within a meter. During Vertical Descent, which is the second to last touchdown milestone, Athena’s GNC system flies the lander to a point approximately 30 km above the Designated Landing Site, and the lander goes into a vertical descent at three meters per second. Importantly, at this point, it then brakes to a one-meter-per-second descent rate 10 meters above the surface, preparing for terminal descent and landing.
However, if the lander is unable to tell its exact distance from the surface, this process can become complicated and lead to a faster than planned, or somewhat uncontrolled touchdown on the Moon. In an interview with Eric Berger the Intuitive Machines CEO Steve Altemus confirmed that the altimeter had failed.
He was quoted saying, “The landing was kind of like sliding into second base,” In other words, it touched down, tipped over, and slid into the crater, breaking a landing leg and possibly rolling over once or twice during that process.
On the day of the landing, during the news conference they actually hinted at this issue. They were quoted saying, “Our laser altimeters, we tested those out, if you recall on the first mission, we had an issue where they wouldn’t fire. We tested those extensively on this mission, and we fired them on the ground before we launched at the Cape. We fired them in orbit at the Moon to make sure we saw power pulses. And then we fired them again in the lunar descent orbit, and that’s where we first saw that there was more noise in the system then we had anticipated.”
“So when we came around for the final approach, we were concerned about the noise we were seeing in those measurements. But at the same time we were seeing better than expected results on our crater tracking. And so the hope was that noise would clean up as we got closer to the Moon because the signal to noise gets stronger. The way these systems work, you have a power pulse that comes back, and that identifies a range measurement. That’s what we were monitoring on the way down and it just remained noisy all the way until touchdown” he said.
This along with the confirmation from the CEO paints a pretty clear picture of what caused Athena to not touch down as gracefully as intended. Without a clear reading from the altimeter, the lander may have been able to tell is relative location to the Moon’s surface but not the exact distance.
As partially mentioned prior, once the lander determines it’s just 10 meters above the surface, it then switches to terminal descent. Terminal descent uses inertial measurements only. No cameras or lasers are guiding the spacecraft to the lunar surface because they would read lunar dust kicking up from the lander’s engine. However, the process in theory would only last about 10 seconds, and if the lander leading up to that milestone isn’t sure its exact distance above the surface, it could easily be moving much faster than it should have by the time it made contact with the Moon.
Unfortunately, this is a similar issue to what happened on the IM-1 mission. In that case, a pre-launch error rendered the laser altimeter unusable. Somewhat ironically, within the IM-2 mission media kit, when talking about the altimeter, they are quoted saying, “and we triple checked it this time.”
On the bright side, it did perform better than the first mission as it provided data up until the final approach. That being said, it again led to a similar landing result and an early end to the mission.
As far as what caused the altimeter issues on Athena, Intuitive Machines has a theory based on some of the initial data. For reference, TRN stands for Terrain Relative Navigation and HRN stands for Hazard Relative Navigation. The CEO was quoted saying, “When we got closer we fired the TRN laser and then we rolled around and fired the HRN laser. What we saw on the TRN laser was these noisy measurements that Tim talked about. So we decided with that one that we couldn’t necessarily trust to automatically ingest those noisy measurements into the common filter, which is part of the NAV system, and it’s weighted as how much you trust that altimeter setting.”
“We were gonna ingest those manually, so we changed the trajectory to evaluate those measurements, determine if they were healthy or noisy, and then we would ingest them in appropriately. The HRN laser though had an interlock signal. Now we fired it in orbit, but an interlock signal came on when we tried to fire it post de orbit insertion, which means that it would not receive return measurements.”
“We waited and we cycled it several times, it actually came on very late in the trajectory, beyond the time we would have used it. We think that there was either vibration or a thermal issue that caused the pin of sorts or connectors to get out of wack and get an intermittent signal. And so there was some event in space to cause that connection to get a bit squirrely on us” he said.
With this in mind, its clear that teams will have one area in particular they will absolutely be focusing on as they work toward IM-3, scheduled to happen early next year.
Mission Outlook
Despite the sideways landing and lack of payload science, the company’s CEO is adamant that this mission is a positive step forward. Intuitive Machines recently released a short article written by the CEO, outlining the mission and their future.
Here he is quoted saying, “Spaceflight is a complex endeavor. It is just the way it is. Aerospace is unforgiving, but it’s where we thrive—pushing boundaries, overcoming challenges, and pulling back the darkness to extend humanity’s reach into the solar system. IM-2 was no exception. For every mission, Intuitive Machines must accept a degree of risk and the possibility of failure. The key to our success is to learn, iterate, and continue moving forward.”
“The goal was audacious: land at the Moon’s south pole, a region marked by jagged terrain, deep craters, and brutal cold. Past missions have avoided this area—where the Sun cuts low across the horizon, casting long shadows that obscure hazards and limit direct data transmission with Earth. It’s also a region that we believe holds the keys to the future of space exploration. Scientists believe frozen water is trapped beneath the surface, and unlocking these resources could fuel humanity’s next leap to the red planet.”
“On March 6, 2025, our lunar lander, Athena, touched down inside a shallow crater on the Mons Mouton region of the Moon after traveling over one million kilometers. This was the southernmost lunar landing ever achieved—a historic step into one of the most extreme environments in the solar system. While Athena was not upright after landing, the mission pressed forward. Our teams accelerated payload operations, including NASA’s PRIME-1 drill suite, transmitting critical data before Athena’s batteries depleted. In just 12 hours of surface operations, we gathered extraordinarily valuable data for our customers, including validating Nokia’s 4G/LTE network operation, proving that our technology and expertise can deliver in the face of adversity.”
“IM-2 also broke new ground in the performance of our proprietary propulsion system, which was designed, 3D printed, and tested in-house. Using renewable cryogenic liquid methane and liquid oxygen—materials present elsewhere in our solar system—IM-2 reached lunar orbit in only five days and validated the complete propulsion system through six main engine firings. We believe this system is also capable of supporting future missions to Mars and beyond.”
He finished by saying, “If someone had told us six years ago that we would attempt something this ambitious with the same outcome, we would have charged forward with the same toughness and competence. The razor-thin margins of lunar success don’t deter us; they define us. IM-2 was another step in proving that Intuitive Machines is not just landing on the Moon—we believe we are leading the way in commercializing space and building the infrastructure for humanity’s next frontier. And we’re just getting started” he said.
When asked about the schedule of IM-3 and whether or not this mission would impact it, they were confident that it would stay on schedule with launch around early 2026. With a similar lander design, they are hoping to prove they can successfully touch down on the Moon’s surface. In theory, based on what we learned from both IM-1 and IM-2, if they can get the altimeter to work as intended, they have a decent chance.
Conclusion
Without a properly working altimeter, the Athena lunar lander wasn’t able to properly judge distance from the Moon’s surface, leading to a faster than planned touchdown. Intuitive Machines believes that either a thermal issue or vibrations during flight messed up the system.