This tiny, trailblazing satellite is taking on a big moon mission

If all goes according to plan, NASA astronauts will go to the moon in an Orion capsule in a few years. The Orion capsule weighs 8.5 tons and occupies a sizable space. On the opposite end of the size spectrum, though, is a spacecraft that might fit neatly on an office desk yet is, in many respects, no less significant to those lunar exploration aspirations.

Its name is CAPSTONE, which stands for Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment. In late June, it will launch for the moon, where it may become the first lunar satellite of its kind. And it's performing a trial run ahead of potential future, glitzier missions. In the not too distant future, CAPSTONE may assist NASA in developing a communications hub that will orbit the moon.

The fellowship of the CubeSat

Despite its modest size, CAPSTONE is noteworthy for a number of factors, many of which are related to the satellite's CubeSat classification.

CubeSats are just that—cubes. The typical base versions have a side measurement of around 4 inches and a weight of no more than 4.5 pounds. Since the majority employ components that are readily available, you might even assemble one by hand. They may be stacked to create bigger satellites. The smallest-yet CubeSat constellation, CAPSTONE comprises 12 of them (which used 16).

1,862 CubeSats have been launched between 1998 and the beginning of June 2022, and by 2028, that number is expected to have more than doubled. Due to their inexpensive cost, CubeSats are accessible to hobbyists, university groups, nascent entrepreneurs, tiny developing nations, and those who lack SpaceX's or the major space agencies of the world's resources.

However, CubeSats have also shown to be attractive for other missions because to their inexpensive price. For $13.7 million in 2019, NASA hired the private company Advanced Space to construct CAPSTONE. (For contrast, even the most basic huge lunar probe may cost an order of magnitude more.) To launch the probe rapidly and affordably into orbit, Advanced Space opted to employ CubeSats.

Earth orbit is home to the great majority of CubeSats. Few have progressed further than that. Two made their way to Mars in 2018 together with NASA's Mars InSight project. No one has ever reached CAPSTONE's target on the moon's orbit.“To date, there have not been lunar cubesats,” according to Jekan Thanga, an engineer at the University of Arizona, who isn’t involved with CAPSTONE. “CAPSTONE is actually going to be a first in that respect.”

The unmanned test flight of Artemis 1 is being accompanied by more CubeSats. They may beat CAPSTONE to the moon, depending on when they launch (currently planned for no sooner than August).

CAPSTONE’s two missions

A Rocket Lab Electron rocket, which is primarily used to launch small satellites into Earth orbit, will carry CAPSTONE into space from New Zealand's Mahia Peninsula. With CAPSTONE, Electron will make his first moonshot. “That’s also a bit of precedent,” Thanga adds.

After a 3.5-month journey, CAPSTONE will enter a strangely lengthy loop around the moon known as a near-rectilinear halo orbit in early November (NRHO). Between 1,000 miles above one pole and 43,500 miles above the other, this varies. It's not simply a pleasant curiosity to enter NRHO. The future Lunar Gateway, a space station that will circle the moon as part of the Artemis program, will test this orbit with CAPSTONE.

“There’s no real uncertainty that the math works,” Cheetham adds, but CAPSTONE will give spacecraft operators practice for getting into that orbit.

CAPSTONE will attempt to communicate with a spacecraft without touching ground control on Earth while it is orbiting the moon. The Lunar Reconnaissance Orbiter, a previous NASA mission that has been surveying the moon's surface since 2009, will attempt to connect with CAPSTONE in order to calculate the locations of both spacecraft. Being able to communicate with nearby satellites is helpful because transmission from Earth to the moon, even at light speed, takes longer than one second.

Thanga speculates that subsequent CubeSats could be able to make such capability more enduring. For instance, it would make it simpler to communicate with the lunar far side, which is now inaccessible from Earth. A second satellite was required to carry communications to and from Earth when the Chinese lander Chang'e-4 landed on the far side of the moon last year.

When lunar satellites communicate with one another, they can more easily avoid collisions and won't need to call on Earth's ground control as often. “What we want to do is prioritize that ground contact,” Cheetham claims that crucial operational data should be transmitted instead of regular location checks.

Communication is king

When the crewed Artemis battles begin—the first is scheduled for 2024—the entire world will probably be watching. The groundwork (or spacework, as it were) for those astronauts must first be laid by small-scale missions like CAPSTONE.

There are more moon missions planned, some of which might launch by the end of this year. In order to assess the viability of future lunar habitation, NASA has contracted with a few businesses to develop a fleet of lunar landers that are outfitted with scientific instruments for analyzing things like subterranean water, the makeup of the moon's surface, and the strength of its magnetic field.

Astronauts will depend on facilities like the Lunar Gateway, which will serve as a communications hub and a distribution hub for humans on the surface, as more and more Artemis missions and astronauts reach the moon. That strategy has drawn criticism; some observers claim that transmitting lunar landings through the Gateway will increase the amount of fuel and energy needed for missions.

But Gateway is only the beginning. Everything from lunar mining to lunar satnav to lunar nuclear power plants is being planned by the space agencies and their partners behind Artemis.

“The feeling is there’s going to be a lot more traffic to the moon,” according to Thanga, “and that requires a lot more infrastructure, including systems like the Gateway”.