NASA’s CAPSTONE CubeSat reaches lunar orbit

NASA’s CAPSTONE mission will reach the Moon on November 13, becoming the first spacecraft to enter a special elongated orbit that could support future space missions. The microwave-sized satellite weighs only about 25 kilograms and will also be the first CubeSat to fly and operate on the moon.

A trajectory correction maneuver on Sep 8 had inadvertently caused the CAPSTONE spacecraft to spin so rapidly that the onboard reaction wheel could not control or counteract the spin. Later on October 7, NASA teams were able to execute recovery commands that stopped this runaway spin.

CAPSTONE mission

CAPSTONE stands for Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment. The mission’s CubeSat was sent into space to test a unique lunar orbit called the Near Rectilinear Halo Orbit (NRHO), which is very elongated and located at a precise balance point between Earth’s and Moon’s gravity.

Over the past four months, the CAPSTONE spacecraft has traveled an unusual but efficient space path to the moon. Dubbed the lunar ballistic transfer, this route follows gravitational contours in space to help the spacecraft reach its destination while using very little power.

The CAPSTONE spacecraft will soon reach the end of its gravity-driven orbit and reach the Moon, where its approach must line up perfectly with the NRHO insertion, which is the critical point of the mission. So far, the spacecraft’s maneuver schedule has been flexible based on its performance and other factors.

But now the orbital insertion has to happen at exactly the right time to ensure CAPSTONE is placed in the right orbit. The spacecraft will fly at over 6,000 kilometers per hour and perform a delicate, precisely timed propulsion maneuver to enter orbit. NASA likens her to a “flying trapeze artist who leaps from one arch to another with a determined, acrobatic movement.”


Because the NRHO orbit is at a precise equilibrium point between Earth’s and Moon’s gravity, it required minimal energy to maintain it, meaning it can be an ideal launch pad for missions to the Moon and beyond. By verifying this orbit, CAPSTONE will help mitigate risks for future spaceflights and could also help establish long-term missions such as the Gateway space station.

In addition to NRHO, CAPSTONE will also demonstrate a key software technology – the Cislunar Autonomous Positioning System (CAPS). CAPS includes an innovative spacecraft-to-spacecraft navigation solution that will allow future missions to determine their location without having to rely on tracking from Earth. CAPSTONE can communicate directly with NASA’s Lunar Reconnaissance Orbiter to determine its own position in space. This software solution will support NASA’s Artemis missions.


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