As seen from this Lagrange point (there are a total of five such points in the Sun–Earth system), the Sun, Earth and Moon will always be close together in the sky, so Gaia can use its sunshield to protect its instruments from the light and heat from these three celestial bodies simultaneously.

This also helps the satellite to stay cool and enjoy a clear view of the Universe from the other side.

L2 provides a moderate radiation environment, which helps extend the life of the instrument detectors in space.

However, orbits around L2 are fundamentally unstable.

“We’ll have to conduct stationkeeping burns every month to keep Gaia around L2, otherwise perturbations would cause it to ‘fall off’ the point,” says Gaia Operations Manager David Milligan.

For those used to seeing images of the International Space Station orbiting Earth, or Mars Express orbiting the Red Planet, it seems intuitive that spacecraft have to orbit something. How do you get a spacecraft to orbit around a point of nothingness?

The experts behind Gaia’s arrival at nothingness

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