A probe the size of a toaster will soon explore 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 space for the astronauts and equipment to travel as part of NASA’s Artemis lunar program. The launch of this small but powerful exploratory probe will inaugurate the Artemis mission and finally launch the space agency’s ambitious lunar projects.
The smart little spacecraft is called the Capstone, or more officially the Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment. It will be placed on top of a Rocket Lab Electron rocket scheduled to explode on June 27 from the Mahia Peninsula in New Zealand at. 21.50 local time (5:50 EDT). If it cannot be launched that day, it will have other options between then and July 27th. Launch operators had planned the launch earlier this month, but decided to postpone it while updating the flight software.
“We are really excited. It will basically be the first CubeSat to be launched and launched to the moon,” said Elwood Agasid, Capstone’s Captain and Vice President of NASA’s Small Satellite Technology Program at the Ames Research Center. “Capstone will serve as a pathfinder to better understand the particular orbit that Gateway will fly in and what the fuel and control requirements for maintaining orbit around the moon are. “
CubeSats pack a lot into small spaces, typically at a lower cost than larger satellites. The “cube” refers to a single standard unit that is about 4 inches on one side. Many CubeSats have a 3U format, with a trio assembled to form a bread-sized configuration. Capstone is a 12U spacecraft, or four of them combined. Everything is designed to fit into the compact box, including a lithium-ion battery and avionics systems, with the electronics and microcontrollers responsible for 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 allows NASA and its commercial partners to determine the exact location of the spacecraft while in the lunar orbit. “On Earth, people take for granted that GPS provides that information,” Bradley Cheetham, chief executive of Advanced Space in Westminster, Colorado, and chief investigator in Capstone, told a virtual news conference in May. But GPS does not extend to the upper Earth orbits, let alone the moon. In addition to Earth’s orbits, scientists are still relying on terrestrial systems to track spacecraft through the Deep Space Network, an international system of giant antennas administered by NASA’s Jet Propulsion Laboratory. Instead, Capstone will provide a spacecraft-to-spacecraft navigation system that takes advantage of the Lunar Reconnaissance Orbiter 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 cross to the moon on a roundabout route called a ballistic moon transfer, which uses little energy but takes three months for the trip. (Astronauts will travel on a more direct orbit in just a few days.) Then Capstone will soar into an oval-shaped, almost rectilinear halo orbit, or NRHO, which orbits the moon over the course of a week, separated from it of 43,500 miles at the farthest point. This path has the advantage that it balances the gravity of the earth, the moon and the sun, thereby limiting fuel consumption, which will be important for the Gateway station.