A toaster-sized probe A special orbit will soon be drawn around the moon, the path planned for NASA’s Lunar Gateway space station. The Gateway, which will be launched later this decade, will serve as a staging point for astronauts and gear that will travel as part of NASA’s Artemis mission to the moon. The launch of this small but mighty wayfinding probe will kick off the Artemis mission and ultimately the space agency’s ambitious lunar program.
This intrepid little spacecraft is called Capstone, or more formally, the Cislunar Autonomous Positioning System technology operation and navigation experiment. It will be housed on the Rocket Lab Electron rocket, which is scheduled to launch on June 27 at 9:50 p.m. local time (5:50 a.m. ET) from New Zealand’s Mahia Peninsula. If the launch doesn’t happen that day, there are other opportunities between then and July 27. The launch operator had originally planned to launch earlier this month, but decided to delay the launch when it updated the flight software.
“We’re really excited. It’s basically going to be the first CubeSat to launch and deploy to the moon,” said Elwood Agasid, Capstone program manager and associate program manager for NASA’s Small Satellite Technology Program at Ames Research Center. “Capstone will act as a pathfinder to better understand the specific orbits the Gateway will fly into and what the fuel and control requirements are to maintain orbit around the Moon.”
CubeSats pack a lot into a small space, often at a lower cost than larger satellites. A “cube” refers to a single standard cell with sides approximately 4 inches long. Many CubeSats come in a 3U format, three combined to form a configuration about the size of a loaf of bread. Capstone is a 12U spaceship, or a combination of four of them. Everything was designed to fit into this compact box, including the lithium-ion battery and avionics system, with the electronics and microcontroller responsible for propulsion, navigation and data processing. Horizontal solar panels extend from the sides of the box like wings.
While there are plenty of spacecraft orbiting the moon, Capstone’s technology demonstration will make it unique. In particular, it includes a positioning system that enables NASA and its commercial partners to determine the precise location of spacecraft in lunar orbit. “On Earth, people take for granted that GPS provides this information,” Bradley Cheetham, CEO of Advanced Space in Westminster, Colorado, and a principal investigator at Capstone, said in a virtual press conference in May. But GPS doesn’t extend beyond Earth’s upper orbit, 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-vessel navigation system, leveraging the already existing Lunar Reconnaissance Orbiter. Cheetham said the pair will communicate with each other and measure their distance from each location, independent of the ground system.
Capstone will cruise to the moon along a circuitous route known as a ballistic lunar transfer, which uses very little energy but takes three months. (Astronauts will travel in a more direct orbit in a few days.) Capstone will then soar into an elliptical near-rectilinear halo orbit, or NRHO, which orbits the moon in one week, 43,500 miles away from its farthest point . The advantage of this path is that it balances the gravitational pull of the Earth, Moon and Sun, thereby limiting fuel usage, which is important for gateway stations.
