CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) is a lunar orbiter that will test and verify the calculated orbital stability planned for the

Lunar Gateway The Lunar Gateway, or simply Gateway, is the first planned extraterrestrial space station in lunar orbit intended to serve as a solar-powered communication hub, science laboratory, and short-term habitation module for government-agency astr ...

space station. The spacecraft is a 12-unit

CubeSat A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSats ...

that will also test a navigation system that will measure its position relative to NASA's

Lunar Reconnaissance Orbiter The Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. Data collected by LRO have been described as essential for planning NASA's future human and robotic missions t ...

(LRO) without relying on ground stations. It was launched on 28 June 2022, arrived in lunar orbit on 14 November 2022, and is scheduled to orbit for six months.

Background

The

is an in-development

space station A space station is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or landing systems. An orbital station or an orbital space station i ...

being planned by several national space agencies since at least 2018, including

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1205 ...

(ESA) and

Canadian Space Agency The Canadian Space Agency (CSA; french: Agence spatiale canadienne, ASC) is the national space agency of Canada, established in 1990 by the ''Canadian Space Agency Act''. The president is Lisa Campbell, who took the position on September 3, 2020 ...

(CSA). The Gateway is planned to be placed in a novel

lunar orbit In astronomy, lunar orbit (also known as a selenocentric orbit) is the orbit of an object around the Moon. As used in the space program, this refers not to the orbit of the Moon about the Earth, but to orbits by spacecraft around the Moon. The ...

that has not been used previously, where it is expected to serve as a communications hub, science laboratory, short-term habitation module, and holding area for rovers and other robots. Gateway is slated to play a major role in NASA's

Artemis program The Artemis program is a robotic and human Moon exploration program led by the United States' National Aeronautics and Space Administration (NASA) along with three partner agencies: European Space Agency (ESA), Japan Aerospace Exploration ...

. Computer simulations indicate that this particular orbit a

near-rectilinear halo orbit A near-rectilinear halo orbit (NRHO) is a halo orbit with slightly curved – or nearly straight – sides between close passes with an orbiting body. The 2022 CAPSTONE mission is the first such orbit in cislunar space, and this Moon-centric orb ...

(NRHO) offers long-term stability with low propellant requirements for orbital station-keeping, by using a precise balance point in the gravities of

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

and the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

that offers a stable trajectory. The main objective of the CAPSTONE mission is to verify the theoretical orbital stability simulations for the Gateway with an actual spacecraft. CAPSTONE will be the first spacecraft to operate in an NRHO. The spacecraft will also test a navigation system called

Cislunar Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predo ...

Autonomous Positioning System (CAPS), which will measure its position relative to NASA's

(LRO) without relying on ground stations.

Spacecraft

The orbiter is a 12-unit

. The US$13.7 million contract was awarded to a private company called Advanced Space,

Boulder, Colorado Boulder is a home rule city that is the county seat and most populous municipality of Boulder County, Colorado, United States. The city population was 108,250 at the 2020 United States census, making it the 12th most populous city in Color ...

, on 13 September 2019 through a federal

Small Business Innovation Research The Small Business Innovation Research (or SBIR) program is a U.S. government funding program, coordinated by the Small Business Administration, intended to help certain small businesses conduct research and development (R&D). Funding takes the f ...

(SBIR) contract. Advanced Space handled overall project management and some of the spacecraft's key technologies, including its CAPS positioning navigation system, while

Tyvak Nano-Satellite Systems Tyvak Nano-Satellite Systems was an American company designing and building satellites. It started as a designer, builder and provider of nanosatellite and CubeSat space vehicle products and services for government and commercial customers. Ty ...

Irvine, California Irvine () is a Planned community, master-planned city in South Orange County, California, United States, in the Los Angeles metropolitan area. The Irvine Company started developing the area in the 1960s and the city was formally incorporated on ...

, developed and built the

spacecraft bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are opposed to specially produced satellites. Bus-d ...

, an
Stellar Exploration, Inc
developed its propulsion systems that used

Hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

Launch

NASA announced on 14 February 2020 that CAPSTONE would be launched aboard a

Rocket Lab Electron Electron is a two-stage, partially recoverable orbital launch vehicle developed by Rocket Lab, an American aerospace company with a wholly owned New Zealand subsidiary. Electron was developed to service the commercial small satellite launch mar ...

booster from the company's new launch site at the

Mid-Atlantic Regional Spaceport The Mid-Atlantic Regional Spaceport (MARS) is a commercial space launch facility located at the southern tip of NASA's Wallops Flight Facility on Wallops Island in Virginia, just east of the Delmarva Peninsula and south of Chincoteague, Virgin ...

(MARS),

Wallops Island Wallops Island is a island in Accomack County, Virginia, part of the Virginia Barrier Islands that stretch along the eastern seaboard of the United States of America. It is just south of Chincoteague Island, a popular tourist destination. W ...

, in

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

. The launch was scheduled for October 2021 but was subsequently delayed and moved to launch from Mahia, LC-1 in New Zealand. The launch contract with Rocket Lab has a value of US$9.95 million, according to NASA. Rocket Lab's new launch pad in Virginia, designated Launch Complex 2, was completed in 2019 and was hoped to be ready to support launches by 2021. The company said the new facility would principally support Electron missions with U.S. government payloads. However, certification of the

Autonomous Flight Termination System In the field of rocketry, range safety may be assured by a system which is intended to protect people and assets on both the rocket range and downrange in cases when a launch vehicle might endanger them. For a rocket deemed to be ''off course'' ...

(AFTS) took longer than anticipated, resulting in the launch site being changed to Mahia. CAPSTONE launched on 28 June 2022. After separating from the second stage, the Rocket Lab's

Photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...

kick stage lifted the orbital apogee into a lunar-transfer orbit over six days by firing the

HyperCurie Curie is a liquid-propellant rocket engine designed and manufactured by Rocket Lab. A monopropellant is used for the propulsion of the third stage/kicker stage of the Electron rocket, as well as the Photon. The composition of the propellant is a ...

bipropellant engine at perigee six times followed by the

trans-lunar injection A trans-lunar injection (TLI) is a propulsive maneuver used to set a spacecraft on a trajectory that will cause it to arrive at the Moon. History The first space probe to attempt TLI was the Soviet Union's Luna 1 on January 2, 1959 which wa ...

(TLI) burn, after which the CAPSTONE spacecraft was deployed on its journey to the Moon. On 5 July 2022, NASA lost contact with the spacecraft shortly after separation from Photon and stated their intention to recover two-way communication with the spacecraft and continue the mission. On 6 July, mission operators re-established contact with the spacecraft. By 30 September, CAPSTONE was "power positive" and on a stable trajectory towards the Moon while the mission operators worked to regain orientation control of the spacecraft. The root cause of the problem was narrowed to a valve on a thruster that is probably partially open, which thus produces thrust whenever the propulsion system is pressurized. On 7 October, the team uploaded recovery commands, stopped the spin, and regained full 3-axis attitude control. It remained on track to insert into its targeted orbit.

Ballistic lunar transfer

CAPSTONE will use a ballistic transfer to the Moon instead of a more conventional direct

Hohmann transfer In astronautics, the Hohmann transfer orbit () is an orbital maneuver used to transfer a spacecraft between two orbits of different altitudes around a central body. Examples would be used for travel between low Earth orbit and Moon, the Moon, ...

. While trajectories of this type take much longer to reach their destination (about four months in this case, compared to about three days using a traditional direct transfer) they significantly reduce the propulsion requirements, which can increase the delivered mass (of the order of 10-15% more mass). After being ejected from

Earth orbit Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi) in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes days (1 sidereal year), during which time Earth ...

by a series of burns of the Photon stage, the spacecraft will reach a distance of about 1.5 million kilometers, where perturbations from the Sun become important. It will then fall back towards the Earth, intercepting the Moon's orbit and finally entering the intended NRHO around the Moon on 13 November 2022.

Mission

Following a three-month trip to the Moon after launch, the CAPSTONE lunar satellite will spend six months collecting data during this demonstration, flying within of the Moon’s North Pole on its near pass and from the South Pole at its farthest.

References