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CAPSTONE Charts a New Path for NASA’s Moon-Orbiting Space Station

Editor’s Note: This feature story was updated June 30, 2022, to correct the distance above the Moon the CAPSTONE spacecraft will be while in its near rectilinear halo orbit, which are 1,000 miles at its closest and 43,500 miles at its farthest.

It will have equilibrium. Poise. Balance. This pathfinding CubeSat will practically be able to kick back and rest in a gravitational sweet spot in space – where the pull of gravity from Earth and the Moon interact to allow for a nearly-stable orbit – allowing physics to do most of the work of keeping it in orbit around the Moon.

Sounds like a heavenly work-life balance, right? Funnily enough – the orbit is formally known in orbital mechanics as a “near rectilinear halo orbit” (NRHO). Which means, if you were able to trace the shape of the orbit, it would look like an elongated oval with sides so long they’re nearly straight. 

The Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (CAPSTONE) CubeSat owned and operated by Advanced Space in Westminster, Colorado, will be the first spacecraft to test this orbit. Researchers want to show the orbit requires less fuel and allows constant direct communications contact with Earth as the spacecraft passes by the Moon.

And NASA has big plans for this unique type of orbit. Engineers expect it will allow them to park bigger spacecraft – including the lunar-orbiting space station Gateway – in orbit around the Moon for about 15 years. 

About six days after launch, CAPSTONE will deploy from the Rocket Lab Photon spacecraft bus and begin its four-month transfer to its NRHO, firing its thrusters to power its journey. After a couple of additional “clean-up” maneuvers, and a critical maneuver that will insert the spacecraft into the NRHO, the spacecraft will occasionally and sparingly fire its thrusters to stay on course, allowing NASA to understand the orbit dynamics for at least six months. 

“CAPSTONE will be precisely controlled and maintained and will benefit tremendously from the nearly-stable physics of its near rectilinear halo orbit,” said Elwood Agasid, deputy program manager of Small Spacecraft Technology at NASA’s Ames Research Center in California’s Silicon Valley. “The burns will be timed to give the spacecraft an extra boost as it naturally builds momentum – this requires a lot less fuel than a more circular orbit would require.”

If viewed from Earth, CAPSTONE’s orbit would repeatedly trace a consistent oval around the Moon as the spacecraft moves from the lunar North Pole to the lunar South Pole. It will take nearly a week to complete a full lunar orbit. While it’s over the South Pole, the spacecraft will be traveling at its slowest and farthest away from the lunar surface – approximately 43,500 miles (70,000 kilometers) above the Moon. Then, as it builds momentum, the spacecraft will travel at its fastest and closest height above the Moon and cross over the North Pole, at only approximately 1,000 miles (1,600 kilometers) high.

“This orbit has an added bonus of allowing Gateway to have optimal communications with future Artemis missions operating on the lunar surface as well as back to Earth,” said Agasid. “This could unlock new opportunities for future lunar science and exploration efforts.”

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CAPSTONE is commercially owned and operated by Advanced Space in Westminster, Colorado. It represents an innovative collaboration between NASA and industry to provide rapid results and feedback to inform future exploration and science missions.  

NASA’s Small Spacecraft Technology program within the agency’s Space Technology Mission Directorate (STMD) funds the demonstration mission. The program is based at NASA’s Ames Research Center in California’s Silicon Valley. The development of CAPSTONE’s navigation technology is supported by NASA’s Small Business Innovation Research and Small Business Technology Transfer (SBIR/STTR) program, also within STMD. The Artemis Campaign Development Division within NASA’s Exploration Systems Development Mission Directorate funds the launch and supports mission operations. The Launch Services Program at NASA’s Kennedy Space Center in Florida manages the launch.