ESA signs off on contracts for lunar data relay and navigation

The European Space Agency (ESA) has inked a deal with a pair of consortia aimed at providing telecommunication and navigation services for Moon missions. Coming under the agency's Moonlight initiative, one consortium is headed by the UK's Surrey Satellite Technology Limited and includes companies such as Airbus and SES as well …

[Pascal Monett]

Satellites in lunar orbit

Do those satellites need to be smaller that what we're using in orbit around Earth ?

Due the Moon's reduced mass, of course.

I'm guessing that we can do geostationary around the Moon, but they might need to be at a lower altitude. In any case, I'm sure they'll get the details worked out. We've been managing satellites for long enough to know what to do. One might even say that there are no new technical difficulties in this project. The biggest hurdle will be, as always, getting the sats into space. Once they're there, the rest should not be a problem.

[Paul Crawford]

Re: Satellites in lunar orbit

The satellites themselves will be much the same size, orbit around the moon probably a little lower but we shall see what they come up with. I suspect not *that* low as they won't want the same sort of constellations size that you see for Earth (~24 active satellites) navigation simply for the cost of putting it up there, and might be willing to accept areas of poor navigation coverage, etc.

[Anonymous Coward]

Re: Satellites in lunar orbit

Geostationary around the Moon is not possible, mostly because the Moon rotates so slowly that the satellite would be further away than the Earth. In fact due to the Moon being tidally locked we appear in a stationary position to a lunar observer. If the advantage of a geostationary orbit is having a single point to focus on then it's made moot by the presence of the Earth. The advantage of satellite constellations is to allow smaller antennae and lower latency which is probably the intention here.

[John Brown (no body)]

Re: Satellites in lunar orbit

"The advantage of satellite constellations is to allow smaller antennae and lower latency which is probably the intention here."

And there's no atmosphere to attenuate the signals either. Or a magnetic field, so the sats will need to be more hardened against solar weather.

[Eclectic Man]

Re: Satellites in lunar orbit

There are various Lagrange points for the Earth-Moon system which would provide a stationary location in the Lunar sky. (https://en.wikipedia.org/wiki/Lagrange_point_colonization), but for an accurate Lunar Positioning System, you'd probably need a fair number of satellites orbiting the Moon.

Intuitively, Lunar-stationary orbit would be around the Earth-Moon distance as the Earth is stationary in the Lunar sky, however, the great mass of the Earth compared to that of the Moon, may complicate things. See, e.g., https://astronomy.stackexchange.com/questions/20499/is-it-possible-to-achieve-a-stable-lunarstationary-orbit-around-the-moon .

[hedge]

And thinking about lunar tourism...

At this stage could the ITU please set the maximum lunar roaming call rate?

[Mike 137]

" one consortium is headed by the UK's Surrey Satellite Technology Limited"

Thank the Maker that brexit didn't cut us off from the ESA. We have decades of valuable contributions already and with luck will continue to have for the foreseeable future.

[werdsmith]

Re: " one consortium is headed by the UK's Surrey Satellite Technology Limited"

SSTL is part of Airbus Defence & Space anyway.

[Phil O'Sophical]

Re: " one consortium is headed by the UK's Surrey Satellite Technology Limited"

Thank the Maker that brexit didn't cut us off from the ESA

How could it? The ESA is not an EU organization, it's a European organization.

[0laf]

Will they remember to include deorbiting as standard with all this new kit that going to be flying around the moon?

[Phil O'Sophical]

That could perhaps be a bit trickier, since just lowering the orbit until atmospheric drag takes over isn't going to be an option.

[Trigonoceps occipitalis]

Keep going down until lithobraking becomes effective.

[Bill Gray]

With some exceptions, lunar orbits tend to be quite unstable. In a lower orbit, you usually crash within months or years if you aren't actively stabilizing the orbit with small maneuvers.

At the Earth-Moon L1 and L2 points, you can appear to 'hover'. For L2, you do need to loop around the point directly over the lunar far side; otherwise, your view/communications to Earth will be blocked by having the moon in the way. Both points are dynamically unstable; depending on how you slide off the balance point, you'll hit the moon or earth or be thrown into heliocentric orbit.

[Spherical Cow]

When an average-size satellite comes down on Earth it's no big deal because the atmosphere neatly burns it up before it hits anything. Lunar satellites coming down will hit the surface hard and fast. Better hope they don't hit a populated base!

[Anonymous Coward]

Better hope they don't hit a populated base!

IIRC, doesn't Moonbase Alpha have shields of some kind? :-)

[The Oncoming Scorn]

Re: Better hope they don't hit a populated base!

Just as well with Koenigs track record.