Near-rectilinear halo orbit (NRHO) in cislunar space, as ilustrated by A.I. Solutions, Inc. using the FreeFlyer software.

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 CAPSTONE mission, launched in 2022, is the first spacecraft to use such orbit in cislunar space, and this Moon-centric orbit will serve as a staging area for future lunar missions. This orbit type could be used with other bodies in the Solar System and beyond.

A halo orbit is a periodic, three-dimensional orbit associated with one of the L1, L2 and L3 Lagrange points. Near-rectilinear means that some segments of the orbit have a greater curvature than those of an elliptical orbit of the same maximum diameter, and other segments have a curvature less than that of an elliptical orbit of the same maximum diameter (taking maximum diameter as that of the smallest circle that contains the whole of the orbit). In the extreme case all segments have zero curvature with four points with infinite curvature (i.e. a polygon). An NRHO requires at least two other bodies (e.g. the Earth and Moon), and thus NRHO orbits are one theoretical solution to the classic three-body problem in gravitational mechanics. Of the three bodies, one is taken to be of negligible mass (the spacecraft).

There are four families of NRHO orbits associated with the L1 and L2 Lagrange points, two each in the northern and southern directions.[1][2] The low perilune orbits are nearly polar. They are nearly stable, minimizing the artificial thrust required for station-keeping.

Planned NRHO usage

Overview of NRHOs around the Moon

By 2018, NASA had begun considering use of a near-rectilinear halo orbit for a future lunar mission,[3][4] and by 2020, an NRHO is the planned orbit for the NASA Lunar Gateway, to be orbiting Earth-Moon L2 in circa 2024. The Gateway orbit is planned to be a highly-elliptical seven-day NRHO around the Moon, which would bring the small space station within 3,000 kilometers (1,900 mi) of the lunar north pole at closest approach and as far away as 70,000 kilometers (43,000 mi) over the lunar south pole.[5][6][7]

By 2022, the company Advanced Space built a 12-unit cubesat to fly on a Gateway precursor mission for NASA. Named CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment), the spacecraft became the first spacecraft to operate in an NRHO lunar orbit from 14 November 2022 after launch on 28 June 2022.[8][9] The mission objective is to test and verify the calculated orbital stability planned later for the Lunar Gateway space station, and the spacecraft will fly the identical orbital parameters planned later for Gateway. It will also test a navigation system that will measure spacecraft position relative to NASA's Lunar Reconnaissance Orbiter (LRO), without relying on ground stations.[7]

NASA/JPL's Lunar Flashlight, a cubesat intended to search for water near the lunar south pole, was also planned to use a near-rectilinear halo orbit,[10] but the satellite failed to reach the NRHO orbit. [11]

Notes

  1. ↑ "Orbit Maintenance and Navigation of Human Spacecraft at Cislunar Near Rectilinear Halo Orbits". NASA Technical Reports Server. 5 Feb 2017. Retrieved 17 Nov 2022.
  2. ↑ "Near Rectilinear Halo Orbit". 28 March 2020.
  3. ↑ NASA Shapes Science Plan for Deep-Space Outpost Near the Moon, space.com, March 2018.
  4. ↑ How a New Orbital Moon Station Could Take Us to Mars and Beyond, space.com, October 2017, video with refs
  5. ↑ Angelic halo orbit chosen for humankind's first lunar outpost, European Space Agency, published by PhysOrg, 19 July 2019, accessed 15 June 2020.
  6. ↑ Halo orbit selected for Gateway space station. David Szondy, New Atlas. 18 July 2019.
  7. 1 2 Foust, Jeff (16 September 2019). "NASA cubesat to test lunar Gateway orbit". SpaceNews. Retrieved 15 June 2020.
  8. ↑ Tavares, Frank (31 May 2022). "CAPSTONE Spacecraft Launch Targeted No Earlier Than June 13". NASA. Retrieved 1 June 2022.
  9. ↑ "CAPSTONE launch delayed to March 2022". 13 October 2021.
  10. ↑ JPL/NASA (November 28, 2022). "NASA's Lunar Flashlight SmallSat readies for launch".
  11. ↑ Foust, Jeff (August 9, 2023). "Clogged propellant lines doomed NASA lunar cubesat mission". SpaceNews. Retrieved August 10, 2023.

References

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