The tiny spacecraft is set to explore an orbit for a planned space station that will travel around the moon and serve as a staging point for future missions.
A TOASTER-SIZED PROBE will soon scope out a special orbit around the moon, the path planned for NASA’s Lunar Gateway space station. The Gateway, to be rolled out later this decade, will be a staging point for the astronauts and gear that will be traveling as part of NASA’s Artemis lunar program. The launch of this small yet powerful pathfinding probe will inaugurate the Artemis mission, finally setting the space agency’s ambitious moon projects in motion.
The plucky little spacecraft is called Capstone, or, more officially, the Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment. It will be perched atop a Rocket Lab Electron rocket scheduled to blast off on June 27 from the Mahia Peninsula of New Zealand at 9:50 pm local time (5:50 am EDT). If it can’t launch that day, it’ll have other opportunities between then and July 27. Launch operators had planned the liftoff for earlier this month but decided to postpone it while updating the flight software.
“We’re really excited. It’ll basically be the first CubeSat launched and deployed to the moon,” says Elwood Agasid, the Capstone program manager and deputy program manager for NASA’s Small Satellite Technology Program at Ames Research Center. “Capstone will serve as a pathfinder to better understand the particular orbit Gateway will fly in and what the fuel and control requirements for maintaining orbit around the moon are.”
CubeSats pack a lot into tiny spaces, typically at a lower cost than larger satellites. The “cube” refers to a single standard unit, which is about 4 inches on a side. Many CubeSats have a 3U format, with a trio joined to form a configuration about the size of a loaf of bread. Capstone is a 12U spacecraft, or four of those combined. Everything’s designed to fit in that compact box, including a lithium-ion battery and the avionics systems, with the electronics and microcontrollers in charge of propulsion, navigation, and data-handling. Horizontal solar panels extend from both sides of the box, like wings.
While plenty of spacecraft have orbited the moon, Capstone’s technology demonstrations will make it unique. In particular, it includes a positioning system that makes it possible for NASA and its commercial partners to determine the precise location of the spacecraft while it’s in lunar orbit. “On Earth, people take for granted that GPS provides that information,” said Bradley Cheetham, CEO of Advanced Space in Westminster, Colorado, and principal investigator of Capstone, at a virtual press conference in May. But GPS doesn’t extend to upper Earth orbits, let alone the moon. Beyond Earth orbit, researchers still rely on ground-based systems to track spacecraft through the Deep Space Network, an international system of giant antennas managed by NASA’s Jet Propulsion Laboratory. Instead, Capstone will provide a spacecraft-to-spacecraft navigation system, taking advantage of the Lunar Reconnaissance Orbiter that’s already there. The pair will communicate with each other and measure the distance between them and each of their positions, independent of ground systems, Cheetham said.
Capstone will cruise to the moon on a roundabout route called a ballistic lunar transfer, which expends little energy but takes three months for the trip. (Astronauts will travel on a more direct trajectory over just a few days.) Then Capstone will soar into an oval-shaped near-rectilinear halo orbit, or NRHO, which goes around the moon over the course of a week, separated from it by 43,500 miles at its furthest point. This path has the advantage of balancing the gravitational pull of the Earth, moon, and sun, thereby limiting fuel usage, which will be important for the Gateway station.
The NRHO is also always in view of the Earth, never behind the moon, so that Gateway will be able to stay in constant communication with other lunar spacecraft and with mission control on Earth, says Marc Bell, CEO of Terran Orbital, which designed and built the spacecraft: “We’re building a comms network for the moon. How much cooler does it get?”
Once Capstone arrives in lunar orbit, its navigation system will be tested, while engineers on Earth monitor its fuel consumption and make sure that it maintains its unique orbit. That will help them gauge how much energy the future Gateway station will likely need. “It’s kind of rare in our field of spacecraft trajectory design to actually get to send a physical experiment up into space before we do the real thing,” says Diane Davis, the mission design lead for NASA’s Gateway program. “I’m super excited to see how it performs out there.”
Once Gateway is built, it will be centered around two crew cabins, which will be connected to a science and cargo module, a service module, an airlock, and other elements. It will be a distant outpost, smaller than the International Space Station, and it will host a handful of astronauts at a time, including those coming from Earth and those using it as a base camp for treks down to the moon.
The Capstone mission involves a collaboration between NASA and industry, and it benefits from the agency’s Small Business Innovation Research program, Agasid says. In addition to Advanced Space, which owns and operates the spacecraft, they partnered with Tyvak Nano-Satellite Systems of Irvine, California, a Terran Orbital company, for the CubeSat platform and with Stellar Exploration of San Luis Obispo, California, for the propulsion system. Rocket Lab provided the Electron launch vehicle and upper stage called Lunar Photon. (A small spacecraft doesn’t need to fly on a huge rocket; the diminutive Electron is only about one-fourth as tall as a SpaceX Falcon 9, and NASA’s Space Launch System towers above that.) All that adds up to just under $10 million in launch costs and slightly less than $20 million in mission costs—an affordable sum for a trip to the moon.
NASA is working with other commercial partners for the Gateway space station, including Northrop Grumman and Maxar for the first crew cabin and the solar electric propulsion system, and with the European and Japanese space agencies. Those first components are scheduled to launch in 2024 on a SpaceX Falcon Heavy, and crew will visit and aid the assembly after that. “Once it’s fully constructed, crew will use it for science and as a staging location for lunar surface missions,” Davis says. “One of the goals is to show these deep-space technologies in action in our nearish neighborhood before we use those to get us out to Mars.”
This summer, NASA will take several other big steps on its journey back to the moon and potential future missions to Mars. First, the agency must decide whether to conduct further tests on the Space Launch System, the massive rocket that will be used for the Artemis 1 launch. The rocket was recently rolled out to the launch pad at Cape Canaveral, and NASA’s SLS team nearly completed a practice countdown test on Monday. If NASA chooses to move ahead with it, the Artemis 1 flight could launch as soon as August. The SLS and an uncrewed Orion spacecraft will orbit the moon and deploy 10 CubeSats for a variety of secondary missions.
Artemis 2, the first crewed mission, will make a lunar flyby in 2024. And then Artemis 3, planned for 2025, will send some astronauts to Gateway while the others will make NASA’s first moon landing since the Apollo program a half-century ago. The crew will also be sporting new space suits for exploring the moon’s terrain.
But first, Capstone has to scout ahead of them and check how well its new navigation technologies work. “We’re excited to demonstrate some of these capabilities and use them for the next mission,” Agasid says. “We’re all impatient, as usual.”
