Rocket Lab
The tiny CAPSTONE spacecraft successfully entered lunar orbit after a journey of about five months, going far beyond the Moon.
“We’ve received confirmation that CAPSTONE has reached near-linear orbit, and this is a huge step forward for the agency,” said Jim Free, NASA’s chief of exploration systems development, on Sunday evening. “It completed its first docking burn a few minutes ago. And over the next few days they will continue to improve their orbit and become the first cube satellites to fly and move on the Moon.”
This is an important orbit for NASA and a special one because it’s really stable and requires very little propellant to hold position. At its closest point to the Moon, this orbit, which takes about a week, passes within 3,000 km of the lunar surface, and at other points 70,000 km away. NASA plans to build a small space station called the Lunar Gateway by the end of this decade.
But before that, the agency starts small. CAPSTONE is a messy, commercial mission, financially supported in part by a $13.7 million grant from NASA. Developed by a Colorado-based company called Advanced Space with the help of Terran Orbital, the spacecraft itself is a modest size, just 12U cubed satellite with a mass of about 25 kg. It can fit comfortably inside a mini fridge.
The spacecraft was launched on 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 manufacturer, Rocket Lab, has stressed the capabilities of the booster and Photon’s upper stage to the maximum to send CAPSTONE on its long journey to the Moon. This was Rocket Lab’s first deep space mission.
After leaving its rocket, the spacecraft traveled to the Moon for about five months, following what’s known as a ballistic lunar transfer that uses the Sun’s gravity to follow a wide orbit. Along the way, flight controllers managed solve the rotation problem otherwise it could cause the spacecraft to disappear. It was a rotary path that brought the spacecraft more than three times the distance between Earth and the Moon before returning, but required relatively little propulsion to reach its destination.
For example, the burn performed by CAPSTONE to enter a near-linear halo orbit on Sunday evening was extremely small. According to Advanced Spacethe vehicle burned its propellant for 16 minutes at about 0.44 Newtons, equivalent to the weight of nine standard printer papers.
CAPSTONE will not only serve as a beacon on this new orbit, confirming the theoretical features modeled by NASA engineers, but will also demonstrate a new autonomous navigation system in and near the Moon. This Cislunar Autonomous Positioning System, or CAPS, is important due to the lack of fixed tracking assets near the Moon, especially as the cislunar environment becomes more populated over the next decade.
The mission is scheduled to operate in this orbit for at least six months.
