After a nearly five-month journey that took it past the moon and back, the small CAPSTONE spacecraft has successfully entered lunar orbit.
“We have received confirmation that CAPSTONE has reached a near straight halo orbit, and this is a huge, massive step for the agency,” NASA Exploration Systems Development Chief Jim Frey said Sunday evening. “It just completed its first burn a few minutes ago. Over the next few days, they will continue to improve its orbit, and they will be the first cube to fly and operate on the Moon.”
This is an important orbit for NASA, and a special one, because it’s really stable, and only requires a tiny amount of fuel to stabilize. At its closest point to the Moon, this almost week-long orbit passes 3,000 km from the lunar surface, and at other points it is 70,000 km away. NASA plans to build a small space station, called the Moon Gateway, here later this decade.
But before that, the agency started small. CAPSTONE is a commercial trick mission that was financially supported, in part, by a $13.7 million grant from NASA. The spacecraft itself was developed by a Colorado-based company called Advanced Space, with help from Terran Orbital, and is of modest size, just 12U cubes with a mass of about 25kg. Fits comfortably inside a mini fridge.
The spacecraft was launched at the end of June on an Electron rocket from New Zealand. The Electron is the smallest rocket to launch a payload on the Moon, and its manufacturer, Rocket Lab, has stressed the capabilities of its booster and upper photon stage to the max to send CAPSTONE on its long journey to the Moon. This was Rocket Lab’s first mission into deep space.
After separating from its rocket, the spacecraft spent nearly five months traveling to the moon, following what is known as a lunar ballistic transfer that uses the sun’s gravity to follow an extended trajectory. Along the way, the flight controllers managed it Solve the spinning problem which could have resulted in the loss of the spacecraft. This was a circular trajectory, taking the spacecraft to more than three times the distance from Earth to the Moon before turning back, but requiring relatively little propulsion to reach its destination.
For example, the burn that CAPSTONE performed on Sunday night to transition into a near-straight-line halo orbit was very small. According to Advanced Spacethe vehicle burned its thruster for 16 minutes at about 0.44 Newtons, which is equivalent to the weight of about nine pieces of standard printer paper.
Not only will CAPSTONE act as an actuator on this new orbit – verifying theoretical properties designed by NASA engineers – it will also demonstrate a new system for autonomous navigation around and near the Moon. This Cislunar Autonomous Positioning System, or CAPS, is important because there is a shortage of stationary tracking assets near the Moon, especially as the cislunar environment becomes more crowded over the next decade.
The mission is scheduled to operate for at least six months in this orbit.
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