ESA's LISA Pathfinder is another part of the search for gravitational waves, and this has now passed a milestone, which is just an amazing feat of technology.
[ (c)
Copyright ESA/ATG medialab ]
Basically, the plan was, to have two detectors, in perfect and permanent freefall through space, so effectively completely "weightless", taking the measurements. T
How they did it (very briefly) was
1. Position the satellite at a point approx 1.5m km towards the Sun, where the gravity from Earth and Sun balance out (orbiting the first Sun–Earth ‘Lagrangian point’, L1.)
2. Release the two detectors so that they float freely within their respective containers
3. Using an incredibly sensitive steering mechanism, "fly" the spacecraft around the detectors! - no force will ever be applied to the free-floating detectors again, save the gravity that keeps them in orbit, and the spacecraft will when necessary make minute adjustments to its position, to keep the freefalling detectors in the centre of their housings.
So, the theory goes, the only thing that can cause a disturbance of the detectors would be a passing gravitational wave.
A fuller explanation of this amazing experimental mission here:
http://m.esa.int/Our_Activities/Space_S ... Pathfinder