An artist’s illustration shows NASA’s Lunar Reconnaissance Orbiter, or LRO, in orbit over the moon as Earth rises in the background. The LRO will serve as a technological link to help open up access to the moon via intra-satellite navigation under the agency's CAPSTONE mission. NASA illustration
Photo Caption & Credits

Cislunar Space

Oct. 7, 2021

The gap between Earth orbit and the moon is open, uncharted, and undefended.

Not much human activity has touched the moon or its surroundings in the half-century since American Apollo astronauts traversed the lunar landscape, but new concerns about China’s interests and motives have leaders in Washington viewing with worry the vast void of cislunar space.

China’s rapid evolution as a global space player and its announced intention to join with Russia in building a joint science base on the moon, raise concerns about what that kind of activity could yield in terms of future capacity to act and potentially wage war in space.  

NASA plans to return American astronauts to the moon for longer periods to a base of its own, as the U.S. gears up its competitive drive in space. And governments and private entities the world over are eyeing the moon as a potential source of mineral wealth or as a place to position communication or space transportation hubs.

Cislunar space—that vast void between terrestrial orbits and the moon—represents both an opportunity and a threat because it is not only empty, for the most part, but essentially indefensible. At least for now.  

You can’t look at that Earth … and say ‘global’ is sufficient enough for our perspective.Lt. Gen. John Shaw, deputy commander, U.S. Space Command

The Space Force and U.S. Space Command were created to address this risk and Defense Secretary Lloyd J. Austin III’s tenets for responsible behavior in space provide a framework for the department to begin assessing its role beyond Earth’s exclusive gravity well. 


Space Force Lt. Gen. John E. Shaw proposes that the world is no longer global. In a speech at the Space Symposium’s annual Space Warfighter Luncheon in Colorado Springs, Colo., the deputy commander of U.S. Space Command introduced “a few new words for our collective lexicon.” Space Command’s area of responsibility is hard to define, he said. Throughout history, a military AOR [area of responsibility] “has always been defined by lines on a map,” Shaw said. “But what drove those lines were a number of things—the terrain, the political context that was there, the demographics of that part of the world, and probably most importantly, the threat that was there.”

Artist’s concepts illustrate initial ideas for a vehicle to transport astronauts, or to perform activities autonomously, on the moon. General Motors and Lockheed Martin are working together on the concept. Courtesy of General Motors and Lockheed Martin

Space Command is different. “For the first time in military history—the first time—an AOR was defined not by geographic lines on a map,” Shaw said. “No, we had a different one, we had an ‘astrographic’ AOR. That’s word No. 1.” The command’s AOR includes not just cislunar space but everything beyond 100 kilometers above Earth.

“You can’t look at that Earth … and say ‘global’ is sufficient enough for our perspective.” 

Thus, he said, the military must start thinking in “superglobal” terms, which he defined as “those things that are relevant to military matters or even geopolitical matters that encompass the globe and the relevant spaces beyond it, too.”

Because “the space domain is really best defined, in terms of terrain, by those beautiful Einsteinian space-time curves known as gravity wells,” Shaw continued, space operators should begin to think about maneuvering “upwell” and “downwell.”

Later, asked by Air Force Magazine whether the U.S. would be able to detect a kinetic weapon launched at Earth from the moon, he answered only indirectly: “We need to get our capabilities to the point where we can easily see it.”

China recently showed it could launch an object from the moon and accurately land it back on Earth. The mission was to return lunar samples to Earth, but the capability— which the U.S. does not currently have—has clear military applications.

Another way China had leapfrogged the U.S. in cislunar space: It placed a lander on the far side of the moon in 2019, the only time that’s been done. Meanwhile, its primary mission accomplished. China has sent its lunar orbiter that was part of the sample return mission to a point in space relative to the Earth and sun around which the spacecraft will basically park in orbit, demonstrating the ability to traverse cislunar space.


To get military professionals oriented to operating in this new frontier, an associate professor at the University of Colorado Boulder, a space executive, and the Air Force Research Laboratory’s Space Vehicles Directorate together published the 23-page article “A Primer on Cislunar Space” in June.

The article, by Marcus J. Holzinger, Cloudstone Innovations CEO, C. Channing Chow, and Peter Garretson, tries to provide a sense of the scale and challenges in such a vast domain: 

  • Scale. The moon’s orbit is nine times farther from Earth than satellites in the highest orbits. Because cislunar space continues past the moon and includes the entire area influenced by the moon’s gravity—including zones where the sun’s gravity adds a third influence—the Space Force’s potential “sphere of interest” is 1,700-times the size of conventional orbital space. 
  • Trajectories. The Air Force and now the Space Force historically catalog the world’s satellites, publishing the most comprehensive open-source data on their orbits. As future spacecraft take up positions in cislunar space, where the moon’s gravity significantly affects spacecraft trajectories, the Space Force will be challenged to provide a similar level of tracking. 
  • Observation. U.S. and allies’ networks of radar and laser-ranging tracking sites aren’t powerful enough to precisely locate objects in cislunar space. Any “active” systems of observation designed for the purpose “would likely require prohibitive levels of power to be effective,” the paper argues. Passive observation, such as telescopes and antennae, however, “can have substantial utility since there is no dependence on ‘pinging’ the object.” But cislunar distances are so great, telescopes and antennae may need to be placed on the surface of the moon or in repeating cislunar orbits to “offer commanding views of nearby space.”

Unlike today’s predictable orbits, trajectories in cislunar space won’t repeat in neat circles or ellipses nor hold to a regular plane as they do around Earth. Instead, “a wide variety of families” or orbits will prove difficult to describe in conventional geometric terms. Most such repeating orbits will also be unstable. 

Sketches of sample cislunar orbits included by the authors of the Primer article look like drawings made by someone who hasn’t quite gotten the hang of their Spirograph set. NASA plans a near-rectilinear halo orbit for its Gateway lunar space station concept. That orbit takes a tighter path when it approaches the moon then swings farther out over a wider swath of sky. The pattern eventually repeats, and a curve is noticeable in graphs of its orbital plane when looked at from the side.

Earth rise: The Earth looms over the Mare Smythii region of the moon, before the Lunar Module and the Command Module separated during the Apollo 11 Mission in 1969. NASA


Getting a jump on NASA’s inevitable need for astronaut mobility on the moon, General Motors, which built the Apollo program’s Lunar Roving Vehicle, joined with Lockheed Martin to begin sketching new vehicle designs more than a year ago. The two are jointly conceiving an entire transportation system for the moon’s surface. As they work through technical challenges such as surviving the cold, dark lunar nights with enough power, or building equipment that can stand up to the brutal lunar surface, they’re developing business models for monetizing that technology. 

Just as satellite service providers aim to own and operate spacecraft and lease capability to the government, GM and Lockheed Martin are intrigued with the idea of owning and operating uncrewed lunar vehicles and selling transportation as a service.

“And not even just transportation,” says Derek M. Hodgins, who leads strategy and business development for lunar exploration campaigns at Lockheed Martin Space. “But it’s things like preparing the surface, leveling it out for landers, excavations when you start talking about resources, transporting materials, working autonomously when the crew’s not there.” 

Their customers could go well beyond NASA, Hodgins says. “We look at the international landscape, and there’s tremendous opportunity.”

Smaller companies are also looking to get in on the action. Shey Sabripour, founder and CEO at CesiumAstro in Austin, Texas, sees big opportunities as the space business expands. After receiving development funding from the Defense Innovation Unit to develop mature phased-array communication technology and a Small Business Innovation Research grant to study its feasibility for lunar operations. Now he envisions the system as part of a distributed communication network “all the way from here to the moon.” 

At Advanced Space in Westminster, Colo., co-founder and CEO Bradley Cheetham recently rounded up his team to start brainstorming about the military’s cislunar expansion. His company’s cubesat mission for NASA is to test navigating the future Gateway space station’s halo orbit. It will trade navigational pings in space with NASA’s Lunar Reconnaissance Orbiter, a new technique being demonstrated in the upcoming CAPSTONE (for Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) mission.

Cheetham says the U.S. needs to gain the ability to track objects in cislunar space and that this capability shortfall is a “today problem,” rather than long term. He wonders what would happen if another country decided to stake out areas in orbit or on the moon for exclusive operations—even in the name of science. He doesn’t perceive a problem with commercial entities to providing tracking and navigation services, such as Advanced Space provides, to both government and private organizations, using the same constellation. Indeed, he imagines helping “to establish these norms of operations as a commercial entity.”


It’s too soon to try to define the limits of U.S. government or military activities in cislunar space. Depending on what assets could eventually be there, protecting government as well as commercial assets is likely to be inevitable, especially if those commercial assets qualify as critical infrastructure, similar to telephone networks, the electric grid, pipelines, or public water and sewer systems. 

For now, space domain awareness is the central mission, as confirmed by Shaw and Lt. Gen. Stephen N. Whiting, commander of Space Force’s Space Operations Command. But the Space Force is still defining the job at hand. 

The military’s adoption of the phrase “space domain awareness” is still relatively recent, younger even than the Space Force itself. Recognizing that space is a warfighting domain and that deterring malicious activity there is a critical national interest is more than just an update to the established discipline of space situational awareness, said Army Gen. James H. Dickinson, commander of U.S. Space Command, in an interview with reporters Aug. 24 at the 36th Space Symposium. 

“One is different than the other,” he said. Space situational awareness “is reporting on where something is in space—characterizing it that way,” he explained. Space domain awareness “is a little bit more complicated,” requiring observers to try to understand and assign motive—“the ‘why’—the intent—behind having something in space and where it is.”

Whiting suggests there’s more to come beyond domain awareness. “Right now that’s the starting place,” he told Air Force Magazine. “Then we’ll look to see if any other missions make sense for the cislunar domain.”