Success! NASA's tiny CAPSTONE probe arrives at the moon

A tiny NASA spacecraft's historic trek to the moon is over.

The 55-pound (25 kilograms) CAPSTONE probe slipped into orbit around the moon on Sunday evening (Nov. 13), becoming the first cubesat ever to visit Earth's nearest neighbor.

The milestone came after a successful engine burn that ended at 7:39 p.m. EST (0039 GMT on Nov. 14), NASA officials said in a brief update.

Related: Why it took NASA's tiny CAPSTONE probe so long to reach the moon

The maneuver put CAPSTONE (short for "Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment") into a near-rectilinear halo orbit (NRHO) around the moon, a highly elliptical path that will also be occupied by NASA's Gateway space station.

NASA plans to launch the first pieces of Gateway, a crucial part of its Artemis program of moon exploration, in 2024. But the agency wants to learn more about lunar NRHOs first, and that's where CAPSTONE comes in: The microwave-oven-sized spacecraft will verify the suspected stability of this orbit, which a spacecraft has never flown in before, during a mission designed to last at least six months.

CAPSTONE will also perform some communication and navigation tests, some of them in concert with NASA's Lunar Reconnaissance Orbiter, which has been looping around the moon since 2009.

CAPSTONE isn't ready to get to work just yet, however; it still needs to fine-tune its path around the moon.

"Two smaller correction maneuvers will take place this week to ensure the spacecraft is confirmed into the complex lunar orbit," representatives of the Colorado company Advanced Space, which owns CAPSTONE and operates the cubesat for NASA, wrote in an update Sunday night.

CAPSTONE's path to lunar orbit was a bit bumpy. The probe launched atop a Rocket Lab Electron booster on June 28, kicking off a circuitous, highly fuel-efficient 4.5-month-long trek that followed gravitational contours.

The CAPSTONE team lost contact with the probe on July 4, just after it separated from Rocket Lab's Photon spacecraft bus. They quickly identified and fixed the problem, an improperly formatted command, getting CAPSTONE back on track the next day.

CAPSTONE ran into more trouble two months later. The probe suffered a glitch during a trajectory-correcting engine burn on Sept. 8; it began to tumble and went into a protective safe mode as a result. 

The mission team traced this problem to a wonky valve in CAPSTONE's propulsion system, troubleshot it, and got the probe back on course for its historic lunar arrival.

Other cubesats will soon follow in CAPSTONE's footsteps, if all goes according to plan. NASA's Artemis 1 moon mission is scheduled to launch on Nov. 16, sending the agency's Orion capsule on an uncrewed shakeout cruise to lunar orbit. Artemis 1 will also loft 10 ride-along cubesats, some of which will study the moon. 

One of those little craft, Japan's OMOTENASHI ("Outstanding Moon exploration Technologies demonstrated by Nano Semi-Hard Impactor"), will even put a tiny lander down on the moon.

Though CAPSTONE is a lunar trailblazer, it isn't the first cubesat to go beyond Earth orbit. That distinction goes to NASA's MarCO-A and MarCO-B probes, also known as Wall-E and Eva, which launched with the agency's InSight Mars lander in May 2018. The two cubesats helped beam home data during InSight's Red Planet touchdown six months later and also managed to photograph Mars.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.