A lunar space station will be placed in an elliptical orbit around the Moon, hovering just 1,860 miles from the surface at closest approach, Nasa and the European Space Agency (ESA) have announced.
The ‘Lunar Gateway’ is due to be built in the 2020s as a staging post for astronauts to travel easily back to the Moon as well as a jumping-off point for reaching further into the Solar System.
Its position will allow trips to and from the Moon every seven days with a lunar lander stationed at the gateway to transport people, robots and infrastructure down to the surface.
The ESA says the station will act ‘like a mountain refuge’ providing shelter and a place to stock up on supplies for astronauts en route to more distant destinations, as well as providing a place to relay communications and a laboratory for scientific research.
It will also be a platform for scientific discovery in deep space and build invaluable experience for the challenges of future human missions to Mars, the space agency said.
Mission planners at Nasa and ESA’s Operations Centre (ESOC) have spent months debating the pros and cons of different orbits, and have now decided where they will place it in space.
Instead of orbiting around the Moon in a low lunar orbit like Apollo, the Gateway will follow an elliptical path.
It was chosen to allow the station to come close to the Moon but also allow quicker access from Earth and easier observations further out into deep space. At its furthest point it will be 43,000 miles from the lunar surface.
Known as a Near-Rectilinear Halo Orbit (NRHO) and the space station will actually be spinning around one of the ‘Lagrange Points’ - known as the ‘parking spaces of space’ where gravitational and centrifugal forces between the Earth and Moon are perfectly balanced.
“Finding a lunar orbit for the gateway is no trivial thing,” said Markus Landgraf, Architecture Analyst working with ESA’s Human and Robotic Exploration activities.
“If you want to stay there for several years, the near rectilinear halo orbit is slightly unstable and objects in this orbit do have a tendency of drifting away”.
To keep the Gateway in position, regular small station-keeping manoeuvres will be required.
The orbit will also help preserve fuel because only small manoeuvre will be needed to slow a visiting spacecraft to rendezvous with the Gateway. Then equipment can be left there until the space station spins around to its closest approach with the Moon.
“To escape Earth’s gravitational pull requires a huge amount of energy,” said: Florian Renk, Mission Analyst in ESOC’s Flight Dynamics Division.
“To then land on the Moon and not hurtle straight past it, we have to slow down by losing that same energy.
“We can save some of this energy by leaving parts of the spacecraft in orbit, taking only what we need to the surface of the Moon.”
Like the International Space Station, the ESA is planning that the Gateway will be a permanent base, with astronauts living on board for months at a time, and regularly travelling to the lunar surface.