cislunar / sis-loo-ner / situated between the Earth and the Moon

Rocket Lab, the first private company in the Southern Hemisphere to reach space, has launched a small, moon-bound spacecraft from its New Zealand facility.

The company’s Electron rocket— a two-stage launch vehicle capable of delivering a 150-kilogram payload to orbit—is carrying a 55-pound, microwave oven-sized spacecraft called CAPSTONE.

CAPSTONE—an acronym for Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment—is the first mission of NASA’s Artemis program, which seeks to return human beings to Earth’s moon.

NASA hopes CAPSTONE will verify that a specific type of moon orbit is suitable for the lunar Gateway space station the agency aims to launch later this decade.

The Lunar Gateway, or simply Gateway, is a planned, small, lunar-orbital space station that will serve as a communication hub, science laboratory, short-term habitation module, and holding area for astronauts and lunar equipment. When [if] complete, Gateway will be the first space station beyond low Earth orbit and the first space station to orbit the Moon.

Gateway’s viability and ultimate success are not dependent upon the CAPSTONE mission. However, information gathered by CAPSTONE would allow NASA to base orbital calculations germane to the Gateway endeavor on actual data, and provide operational experience in the mechanics of near-rectilinear Halo orbits (NRHO)—a periodic, three-dimensional orbit around the point of gravitational equilibrium (Lagrange point) between two massive celestial bodies [the Earth and the Moon] and one small body [the CAPSTONE spacecraft]. NRHO orbits are one theoretical solution to the classic three-body problem in gravitational mechanics.

Anyway …

Currently in orbit around the Earth, Photon will next fire its engine multiple times over the coming days before sending the CAPSTONE spacecraft on a trajectory that will take about four months to reach the moon. Once there, CAPSTONE will stay in orbit around the moon for at least six months to collect data.

Assisted by the Sun’s gravity, CAPSTONE will reach a distance of 963,000 miles from Earth – more than three times the distance between Earth and the Moon – before being pulled back towards the Earth-Moon system.

Unlike the Apollo lunar missions of the 1960s and 70s, which took a free return trajectory to the Moon, this fuel efficient ballistic lunar transfer makes it possible to deploy CAPSTONE to such a distant orbit using a small launch vehicle. This gravity-driven track, though time-consuming, dramatically reduces the amount of fuel required to establish CAPSTONE in lunar orbit.

FMI: www.nasa.gov