The Bistromathic I, medicine the Golgafrincham B-Ark, the starship Titanic were all unique in their own ways. However, the ship that sticks in the mind of most people who have experienced the HHGTTG in one shape or form is the Heart of Gold. An amazingly advanced starship with the ability to pass through every point in the universe at the same time (thanks to a very hot cup of strong tea).
On the 2nd December, the European Space Agency (ESA) will launch its own Heart of Gold into space. LISA Pathfinder is unique, in that at the centre of this spacecraft, it carries not one, but two hearts made of gold and platinum, isolated from the noise of the rest of the universe and testing techniques that will allow a future mission to ‘hear’ the gravitational heartbeat of the cosmos.
The 2kg cubic reference masses carried in the centre of LISA Pathfinder are designed to be identical to the ones which – if the tests work as they are expected – will be taken by a future mission, currently called LISA (which stands for Large Interferometry Space Antenna). In LISA Pathfinder, these masses are separated by a few centimetres, while in the full-scale mission the separation is in the order of millions of kilometres.
The gold cubes are carried in special chambers which, together with the rest of spacecraft, are designed to ensure that noise from every possible source; thermal radiation, vibration or the solar wind, does not affect the way these masses float in space. It is as if they were floating in a huge universe where the only change is caused by gravity – and it is gravity that the future LISA mission is attempting to detect. When a distortion caused by a gravity wave passes one of the cubes, space (as in “time and space”) between it and other cube will be changed. This is detected by a complex set of lasers which reflect off the cube. This sounds more-or-less simple until you realise that the changes that LISA will try to measure will be less than the width of an atom – over a five million kilometre span. This is why the isolation of the cubes has to be absolute. Even the heat coming from the spacecraft systems is enough to cause thermal vibrations in the cube; the electronics that are controlling the laser could cause magnetic fluxes to pass through them or the mass of the spacecraft itself could create an uneven environment for the experiment.
The science operations for this mission are being coordinated by ESA’s European Space Astronomy Centre (ESAC) near Madrid, Spain. Here, the planning for the mission, ensuring that the goals forthe experiments will be achived, has been reaching a frenetic pase over the last few months. With such a unque mission in hand, new technoques have to be applied and novel approaches to common problems have been developed. Not an easy task!
LISA Pathfinder, therefore, is an important step on the way to a full space-based gravity observatory. Flying at the Lagrange L1 point (a cusp in the Earth/Sun gravity field) to avoid the effects of the mass of the Earth and Sun; the mission will test the calculations of hundreds of European scientists and engineers to make sure that they have created one of the quietest places in the universe. Where a ship with a heart of gold can fathom the infinitely improbable; detecting the heartbeat of the stars.