IM-1 Lands Safely, Achieves First U.S. Soft Lunar Touchdown Since Apollo 17

Intuitive Machines’ IM-1 lander returned this image from low lunar orbit on Wednesday, a day prior to its successful touchdown near Malapert A. Photo Credit: Intuitive Machines

America has successfully made soft landfall on the Moon for the first time in over five decades, following Thursday evening’s 6:23 p.m. EST touchdown of Intuitive Machines’ six-legged IM-1 lander in the rugged hinterlands bordering the Lunar South Pole. Laden with ten payloads for NASA, the International Lunar Observatory (ILO), the University of Colorado at Boulder, Embry-Riddle Aeronautical University, Louisiana State University and others, IM-1’s Nova-C lander—named “Odysseus” in honor of the much-traveled hero of the Trojan War—will spend up to two weeks probing a little-known region of the Moon that is tipped as an ideal location for exploration and settlement by future Artemis astronauts.

“After troubleshooting communications, flight controllers have confirmed Odysseus is upright and starting to send data,” Intuitive Machines noted on X. “Right now, we are working to downlink the first images from the lunar surface.”

Video Credit: NASA

“On the eighth day of a quarter-million-mile voyage—a voyage along a great cosmic bridge, from the launch pad of the Kennedy Space Center to the target of the South Pole of the Moon—a commercial lander, named Odysseus, powered by a company called Intuitive Machines, launched upon a SpaceX rocket, carrying a bounty of NASA scientific instruments, and bearing the dream of a new adventure,” said NASA Administrator Bill Nelson. “A new adventure in science, innovation and American leadership in space. Well, all of that aced the landing of a lifetime.

“Today, for the first time in more than half a century, the U.S. has returned to the Moon,” Mr. Nelson continued. “Today, for the first time in the history of humanity, a commercial company, an American company, launched and led the voyage up there. And today is a day that shows the power and promise of NASA’s commercial partnerships.

A map of high-resolution Lunar Reconnaissance Orbiter (LRO) data captures the northern half of the south polar region. Shackleton Crater and the pole itself are at bottom; the IM-1 landing site is identified by the red star at top. Malapert Massif is the mountain at center. Credit: NASA/ASU/SESE.

“What a triumph,” the administrator concluded. “Odysseus has taken the Moon!”

Following last month’s loss of Astrobotic’s Peregrine mission, which succumbed to a propellant leak shortly after its 8 January launch and was rendered unable to achieve its planned lunar landing, IM-1 was the first all-up test of Intuitive Machines’ Nova-C lander. And with today’s success, it became the first time a U.S.-built spacecraft has soft-landed on the Moon’s surface since the Apollo 17 Lunar Module (LM) “Challenger” alighted in the Taurus-Littrow Valley in December 1972.

Launch of the IM-1 mission occurred on 15 February, after a daylong delay caused by off-nominal liquid methane temperatures. Photo Credit: Jeff Seibert/AmericaSpace

IM-1 was also the first successful Moon landing under the NASA-led Commercial Lunar Payload Services (CLPS) initiative, which seeks to encourage the U.S. commercial space sector to develop, build and fly its own payload-laden landers. NASA unveiled CLPS in May 2018 and Houston, Texas-based Intuitive Machines was selected the following November as one of nine initial U.S. companies eligible to bid for missions.

In May 2019, the space agency awarded Intuitive Machines contracts worth $77 million to deliver a group of scientific payloads emphasizing plume-surface interactions, space weather/lunar surface interactions, radio astronomy, precision landing techniques and a communications and navigation node for future autonomous technologies to Oceanus Procellarum (the “Ocean of Storms”), at 25 degrees North latitude, near the Moon’s equator, by July 2021. More recently, last May IM-1’s landing site was shifted close to the 15-mile-wide (24-kilometer) Malapert A crater, which sits in the southern lunar highlands at 80.4 degrees South latitude, about 190 miles (300 kilometers) from the South Pole.

The second stage of the Falcon 9 rocket which propelled Odysseus into space drifts slowly into the distance. Photo Credit: Intuitive Machines

This location has long been proposed as an ideal site for human exploration and its position within the “shadow” of transmissions from Earth blocks radio noise from the Home Planet and renders it ideal for the emplacement of future radio telescopes. “The decision to move from the original landing site of Oceanus Procellarum was based on a need to learn more about terrain and communications near the Lunar South Pole, which is expected to be one of the best locations for a sustained human presence on the Moon,” NASA noted. “Landing near Malapert A also will help mission planners understand how to communicate and send data back to Earth from a location that is low on the lunar horizon.”

After a one-day delay induced by “off-nominal methane temperatures” during efforts to load propellants aboard Odysseus, the IM-1 mission got underway at 1:05 a.m. EST Thursday, 15 February, the Falcon 9 boosting it off the planet and via a pair of second-stage engine “burns”—a customary six-minute firing, then a 34-minute phase of coasting, ahead of a final firing, lasting only 53 seconds—deploying the spacecraft into the inky blackness some 48 minutes and 24 seconds after liftoff.  

The entire illuminated disk of the Earth fits within Odysseus’ field of view in this image from the first day of the IM-1 mission. Australia features prominently at center. Photo Credit: Intuitive Machines

“Deployment of @Int_Machines IM-1 confirmed,” tweeted SpaceX as the six-legged Odysseus lander drifted serenely away into the inky blackness to begin her week-long voyage to the Moon.

In those opening hours, the spacecraft autonomously powered-up its sensors and radios without incident, although at one point its navigation system rejected star tracker data, a glitch quickly corrected with an uplinked software patch. “Initially, the star tracker information was numerically conditioned slightly differently than we anticipated,” Intuitive Machines explained in a 15 February update.

Several key features of the IM-1 Odysseus lander, including wiring, a landing leg, and a helium tank wrapped in Columbia Sportswear’s insulation, are captured by an engineering camera. Photo Credit: Intuitive Machines

“We were expecting a one-in-a-thousand numerical tolerance and received a number more like two and three in a thousand,” it was added, prompting Odysseus’ navigation system to reject the data. “When we tested this system terrestrially, they were within tolerance, but we experienced slightly different numerical conditioning in flight.”

During the almost-week-long transit across the gulf of cislunar space which separates Earth and the Moon, Intuitive Machines allocated a Commission Maneuver (CM) and three Trajectory Correction Maneuvers (TCMs) by Odysseus’ VR-900 engine, the first engine fueled by liquid oxygen and liquid methane ever used in space. Citing a complicated “learning process” as teams nursed their spacecraft through its first days in space, the CM was postponed from 15 February.

Video Credit: Intuitive Machines

“Communication delays and outages are expected when executing lunar missions, which we accounted for in our mission planning,” Intuitive Machines explained. Intermittent uplink and downlink communications from Odysseus carried the potential to negatively impact “our ability to collect the critical information required to support the CM burn and follow-on performance analysis”.

One observed oddity was that the VR-900 liquid oxygen feed line took longer to chill down in space than it had done in tests on the ground. “After understanding the in-space liquid oxygen feed line requirements,” Intuitive Machines noted, “we adjusted and uploaded the CM burn preparation timeline and increased the on-board event sequence timer.”

An artist’s impression of the IM-1 Lunar Orbit Insertion (LOI) burn. Image Credit: Intuitive Machines

The 21-second-duration CM burn was completed without incident on 16 February at a distance of more than 167,000 miles (270,000 kilometers) from Earth. “This engine firing included a full-thrust main-stage engine burn and throttle-down profile necessary to land on the Moon,” tweeted Intuitive Machines in its summary.

Subsequent data analysis revealed that the CM burn allowed Odysseus to hit its 68.8-feet-per-second (21 meters per second) targeted velocity with an accuracy of 2.6 feet per second (0.8 metres per second). “Propulsion mixture ratios, mass flow rate and temperature were as predicted,” it was added, and the overall performance of the CM burn was characterized as “nominal and per expectations”.

The first pair of TCMs were conducted on 18 and 20 February, with the second of these burns considered of sufficient precision to eliminate the need for a TCM-3. Finally, earlier today Odysseus fired its VR-900 engine for 408 seconds to enter a circular lunar orbit at a mean altitude of 57 miles (92 kilometers). The 2,600-feet-per-second (800-meters-per-second) Lunar Orbit Insertion (LOI) was completed with an accuracy of less than 6.6 feet per second (2 meters per second).

A lunar correction maneuver, conducted to raise Odysseus’ orbit overnight 21/22 February led to a revised landing time of 4:24 p.m. EST Thursday, but a delay of two hours and one revolution of the Moon was inserted into the timeline. “Flight controllers chose to exercise an additional orbit before starting the IM-1 mission landing sequence,” Intuitive Machines tweeted Thursday afternoon, with a new landing time of 6:24 p.m. EST.

As circumstances transpired, Odysseus touched down a minute earlier than that, at 6:23 p.m. EST. It was the first U.S. soft-landing on the Moon in more than 50 years.

IM-1’s suite of payloads includes six instruments from NASA: an array of laser retroreflectors and a sophisticated navigational lidar for precise ranging, a lighthouse-like navigation demonstrator, an investigation into how well future Moon-based radio observatories might function on the Moon, an experiment to explore the response of lunar regolith to rocket exhaust and an innovative propellant mass gauge.

Video Credit: Intuitive Machines

Also aboard is Embry-Riddle University’s EagleCam CubeSat, ejected shortly before IM-1 touches down to acquire the first third-person views of a lunar landing. Louisiana State University has supplied its Tiger Eye-1 radiation monitoring instrument and the ILO-X experiment will evaluate precursor technology for a future planned astrophysics observatory for emplacement near the Moon’s South Pole.

Rounding out the IM-1 payload suit is Moon Phases, a set of sculptures created by award-winning artist Jeff Koons. It stands to become the first artwork of its kind to reach the lunar surface since Apollo 15 Commander Dave Scott left the “Fallen Astronauts” memorial in the dust of Hadley-Apennine in August 1971.

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