On Wednesday morning, a robotic lunar lander launched by a Houston company got closer to reaching the moon.
The company, Intuitive Machines, announced that its Odysseus spacecraft had fired its engine for six minutes and 48 seconds, slowing it enough to be pulled by the moon’s gravity into a circular orbit 57 miles above the surface.
On Thursday, it is scheduled to touch down on the moon. If all goes well, it will become the first private spacecraft ever to make a soft landing there and the first American mission to arrive there since Apollo 17 in 1972.
When is the landing and how can I watch it?
Odysseus is expected to land on the lunar surface no earlier than 5:30 p.m. Eastern time on Thursday. Although it is a private mission, the main customer is NASA, which paid $118 million for the delivery of six instruments to the moon. NASA TV will stream coverage of the landing beginning at 4 p.m. on Thursday.
Where is the spacecraft going to land?
Odysseus is aiming for a spot in the south polar region, a flat plain outside the Malapert A crater. (Malapert A is a satellite crater of the larger Malapert crater, which is named after Charles Malapert, a 17th-century Belgian astronomer.)
The landing site is about 185 miles from the moon’s south pole.
Some of those craters in that region remain in perpetual shadow, and are a particular area of interest because water ice has been detected in them. Previous American moon missions have landed in the equatorial regions.
How will Odysseus land?
The spacecraft will fire its engine so that the circular orbit changes to an elliptical one, and will drop to within about six miles of the lunar surface. From this point onward in the landing sequence, Odysseus will operate completely on its own. After coasting for an hour, the engine will start up again, and the spacecraft will begin its powered descent. It will have to slow down from its initial speed of about 4,000 miles per hour.
Odysseus will track its position through cameras, matching the patterns of craters with stored maps and measuring its altitude by bouncing laser beams off the surface.
About 1.2 miles from the landing site, the spacecraft will pivot to an upright orientation, with sensors looking for a safe spot.
For the last 50 feet or so of the descent, Odysseus will rely solely on its inertial measurement units, which act as the spacecraft’s inner ear, measuring the forces of acceleration. It will stop using the camera and the altitude-measuring laser to avoid being fooled by dust kicked up by the engine’s exhaust.
What will the lander do on the moon?
Because solar panels provide the spacecraft’s power, its mission will last only about seven days until the sun sets on the landing site. That’s when a two-week long, frigid lunar night begins, and Odysseus was not designed to survive those conditions.
The six NASA instruments carried to the moon by Odysseus and what their tasks are:
A laser retroreflector array that bounces back laser beams.
A LIDAR instrument that precisely measures the spacecraft’s altitude and velocity as it descends to the lunar surface.
A stereo camera that will capture video of the plume of dust produced by Odysseus’ engines during landing.
A low-frequency radio receiver that measures the effects of charged particles on radio signals near the lunar surface, providing information that could aid the design of future radio observation on the moon.
A beacon, Lunar Node-1, that will demonstrate an autonomous navigation system.
An instrument in the propellant tank that uses radio waves to measure fuel levels.
The lander is also carrying other payloads, including a camera built by students at Embry-Riddle Aeronautical University in Daytona Beach, Fla.; a precursor instrument for a future moon telescope; and an art project by Jeff Koons.
How’s the mission going, so far?
Mostly very well.
On Feb. 15, a SpaceX Falcon 9 rocket sent Odysseus on a trajectory toward the moon. After the spacecraft separated, it successfully turned itself on. An initial engine burn to test the propulsion system was postponed because the liquid oxygen propellant took longer to chill down than ground-based tests had predicted.
Engineers adjusted the ignition procedures, and the burn was successfully performed on Feb. 16.
Along the way, the spacecraft transmitted photographs taken of both Earth and the moon.
Flight controllers fired the engine twice more, on Feb. 18 and Feb. 20, to fine-tune the spacecraft’s path to the moon. The second effort was precise enough that the flight controllers decided to skip a planned third correction.
How big is the spacecraft?
The Intuitive Machines lander is a hexagonal cylinder with six landing legs, standing about 14 feet tall and five feet wide. For fans of “Dr. Who,” the science fiction television show, the body of the lander is roughly the size of the Tardis, the time-traveling spacecraft that, on the outside, looks like an old British police telephone booth.
At launch, with a full load of propellant, the lander weighed about 4,200 pounds.
Why isn’t NASA running this mission?
Odysseus is part of NASA’s Commercial Lunar Payload Services program, which allows private companies to send experiments to the moon and spares NASA from building and operating its own moon landers.
The space agency hopes this approach will be much cheaper, letting it send more missions more frequently while it is preparing for U.S. astronauts to return to the moon as part of its Artemis program.