A small CubeSat, about the size of a microwave oven and weighing only 55 pounds (25 kilograms), will be the first spacecraft to test a unique elliptical lunar orbit as part of the lunar autonomous positioning system technology operation and navigation experiment (capstone)
As a pathfinder of the lunar gateway, capstone is part of NASA's Artemis program. It will help reduce the risk of future spacecraft by verifying innovative navigation technology and the dynamics of this halo orbit.
The orbit -- officially known as the near right angle halo orbit (nrho) -- is clearly elongated. It is located at the precise balance of the gravity of the earth and the moon, which provides stability for long-term missions such as the lunar portal and requires only minimal energy to maintain. Capstone's orbit also establishes a location - an ideal staging area for missions to the moon and elsewhere. The orbit will keep capstone in the range of 1000 miles (1600 kilometers) when approaching one pole of the moon and 43500 miles (70000 kilometers) from the other pole at the peak every seven days, which makes it less demanding for propulsion on the lunar surface than other circular orbits.
After a three-month journey to the target destination, capstone will travel around the region of the moon for at least six months to understand the characteristics of the orbit. Specifically, it will verify the power and propulsion requirements predicted by NASA's model to maintain its orbit, which reduces logistical uncertainty. In addition, it will demonstrate the reliability of innovative spacecraft to spacecraft navigation solutions and the ability to communicate with the earth. In addition to covering the south pole of the moon, nrho also provides the advantage of an unobstructed view of the earth.
To test these new navigation capabilities, capstone has a second dedicated payload flight computer and radio and will perform calculations to determine the position of CubeSat in its orbit. NASA's Lunar Reconnaissance Orbiter (LRO) has been orbiting the moon since 2009 to serve as a reference point for capstone. Its purpose is to make capstone communicate with LRO directly, and use the data obtained from this cross link to measure how far it is from LRO and how fast the distance between them changes, which in turn determines the position of Capstone in space.
This point-to-point information will be used to evaluate capstone's autonomous navigation software. If successful, the software, called the Earth Moon space autonomous positioning system (CAPS), will enable future spacecraft to determine their position without relying entirely on tracking from the earth. This capability allows future technology demonstrations to be performed on their own without ground support and allows ground antennas to prioritize valuable scientific data over more conventional operational tracking.
Capstone is scheduled to be launched by rocket lab's electron from the company's launch site 1 in New Zealand no earlier than may 2022. Capstone has a very ambitious timetable that will demonstrate key business capabilities. NASA partners will test cutting-edge tools for mission planning and operation and pave the way and expand opportunities for small and more economical space and exploration missions to the moon, Mars and other destinations throughout the solar system.
