2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
NASA and ESA have approved a near-rectilinear halo orbit as the trajectory of the future Lunar Orbital Platform - Gateway, according to an ESA press release. This orbit combines several advantages, including relatively easy access to the Earth and the Moon, constant visibility of the Earth for communications, and low orbit maintenance costs.
The Lunar Orbital Platform - Gateway is an orbital station that NASA, together with ESA, Roscosmos and JAXA, plans to begin deploying near the Moon in 2022. It will be used for manned missions to the lunar surface, scientific research, and also as a project to test technologies for future Mars missions. Details about this project can be found in our material "Intermediate Station".
Choosing an orbit is often a difficult stage in mission preparation, but in the case of a visited orbital station near the Moon, it is even more difficult. The fact is that the orbit must satisfy several parameters at once, including it must have low characteristic velocities for a flight from the Earth and the Moon. In addition, it is desirable that the station always be able to communicate with the mission control center. Also, the orbit must be stable enough so that it does not have to spend a lot of fuel to maintain it. Finally, there is another unobvious parameter - the magnitude of the heat flux arising from the reflection of sunlight by the Moon.
Orion spacecraft flight diagram with arrival to the selected orbit and return from it to Earth, as well as calculation of the total required characteristic velocity
A few years ago, NASA specialists carried out calculations by comparing different orbits, and came to the conclusion that, in terms of the sum of the key parameters, a halo orbit close to rectilinear (near-rectilinear halo orbit) would be optimal. Usually, a halo orbit means an orbit around one of the Lagrange points far from both celestial bodies of this system. The proposed orbit is a special case of the halo orbit around the L2 point, but in fact it is similar to the usual high elliptical orbit around the Moon. However, due to the interaction with the Earth-Moon system, the plane of this orbit will rotate with the Moon, due to which it will always be turned towards the Earth and available for direct communication without the need for a relay satellite like the Chinese "Queqiao".
The orbit chosen by NASA and ESA specialists has a pericenter of 3,000 kilometers and an apocenter of 70,000 kilometers. The period of revolution of the station around the moon will be almost seven days. This is a disadvantage of the orbit compared to the orbits of the Apollo missions, because the launch window for taking off from the Moon and transferring to the station will open every seven days.
Comparison of the selected orbit with others
Deployment of the station is expected to begin in 2022 with the arrival of the first service module. In 2024, the first manned expedition to the station using the Orion spacecraft is to take place. Prior to this, the ship will perform one unmanned and one manned mission with a flyby of the moon. In late 2018, NASA received a service module from ESA for its maiden flight, and recently the ship's emergency rescue system was successfully tested in flight.