Rocket laboratory
After a nearly five-month journey that took it far beyond the Moon and back, the tiny CAPSTONE spacecraft successfully entered lunar orbit.
“We’ve received confirmation that CAPSTONE has entered a near-rectilinear halo orbit, and that’s a big, big step for the agency,” Jim Free, NASA’s head of intelligence systems development, said Sunday evening. “It completed its first insertion burn a few minutes ago. And over the next few days, they will continue to refine their orbit and become the first lunar probe to fly and operate.”
This is an important and special orbit for NASA because it is really stable and requires very little fuel to get into position. At its closest point to the Moon, this orbit of about one week passes 3000 km from the surface of the Moon, and at other points 70,000 km. NASA plans to build a small space station called the Lunar Gateway here later this decade.
But before that, the agency starts a small business. CAPSTONE is an unconventional, commercial mission funded in part by a $13.7 million grant from NASA. The spacecraft itself, developed by a Colorado-based company called Advanced Space with help from Terran Orbital, is modest in size, at 12U cubic meters with a mass of about 25 kg. It can easily fit inside a mini-fridge.
The spacecraft was launched by an Electron rocket from New Zealand at the end of June. Electron is the smallest rocket to launch a payload to the Moon, and its developer, Rocket Lab, maximized the capabilities of the booster and its Photon upper stage to send the CAPSTONE on its long journey to the Moon. It was Rocket Lab’s first deep space mission.
After separating from the rocket, the spacecraft traveled to the Moon for about five months, following what is known as a ballistic lunar transfer, which uses the Sun’s gravity to follow a wide trajectory. Along the way, air traffic controllers managed it solve the rotation problem which would otherwise have resulted in the loss of the spacecraft. It was a circuitous route that brought the spacecraft three times the distance between the Earth and the Moon before returning, but required relatively little fuel to reach its destination.
For example, the burn performed by CAPSTONE on Sunday evening was too small to enter a halo orbit close to the straight line. According to Advanced Spacethe car burned its thrust for 16 minutes at about 0.44 newtons, which is about the weight of nine standard pieces of printer paper.
CAPSTONE will not only play a pathfinder role in this new orbit—testing theoretical properties modeled by NASA engineers—but also demonstrate a new autonomous navigation system around and near the Moon. This Cislunar Autonomous Positioning System, or CAPS, is important because there is a lack of stable tracking tools near the Moon, especially as the cislunar environment becomes denser in the coming decade.
The mission is planned to operate in this orbit for at least six months.
