It will doubtless carry fuel to stableize, and there may be need for occasional adjustments, but not a lot. My understanding is that an object cannot occupy the actual lagrange point, but can slowly orbit it. And I believe lagranges 2 and 5 are negative, while 1, 3 and 4 are positive.

Gaia will be our first outpost at EL-2, so watching her might prove interesting.

Well, again, gotta log out.

Cheers.

An object placed there will not remain locked to the spot, but will tend to drift around it, which is what I suspect the little red circle is in the orbital diagram I posted. How far this drift is I do not know (the diagram is not to scale).

I know objects at the Lagrangians drift relative to them (like the Trojan asteroids) but I don’t know if this drift is limited to the orbital plane or if there is a component orthogonal to it. Gaia will drift along the ecliptic, but she may also drift above and below it as well. Again, I don’t know.

The moon’s orbit is inclined five degrees to the ecliptic plane, so the moon will sometimes appear 5 degrees above earth (as seen from L2) and sometimes five degrees below (“above and below” refer to ecliptic, not celestial, N and S). And of course, the ecliptic is inclined 23.5 degrees to the celestial equator.

I wonder if the spacecraft carries maneuvering fuel to allow it to stay on location, or if its Lagrangian position is sufficient to keep it on station.

With the Moon’s rotation, there may also be periods of total radio blackout with the vessel, much as we observed when the Apollo craft orbited the Moon. This, too, should pose no problem.

I brought up Lagrange Point 2 because which Lagrange was not mentioned in your post, nothing more.

Incidentally, relevant to other recent discussions…

This is a European Space Agency spacecraft launched by the French on a Russian rocket. NASA is nowhere to be seen.

It is no criticism of the private space industry that this is strictly a government project. Only governments can afford missions like this, that regardless of their potential future value, they would be impossible to sell to private investment, or within the reach of even the most philanthropic entrepreneur. There is simply no forseeable return on investment on this mission within our lifetime, and the scientific community eager to see this data could not come up with the subscription fees to pay for the product.

It is the tax dollars of millions of people who haven’t the slightest interest in this mission, the tiniest desire to pay for it, or any hope of benefitting from it, that have made it possible.

OTOH, there is always a chance this “basic research” mission, or others similar to it, may stumble onto something so profound and unexpected that it could turn into a real game changer for the private space industry. Let’s keep our fingers crossed.

Basic research in astrometry has already led to two fundamental scientific revolutions with incalculable “practical benefits”. Tycho Brahe’s high-precision star catalogues led directly to Kepler’s confirmation of the Copernican cosmology, and then by extension, to Newton’s Laws of Motion.

And precise measurements of anomalies in Mercury’s orbit suggested General Relativity to Dr Einstein. You never know what will come from astronomical navel-gazing.

The L-2 point is far enough away from earth that (combined with its libration around L-2) shadows and eclipses will have little or no effect on the mission.

Just thought I’d throw that in.
;^)