LISA Pathfinder takes major step in hunt for gravitational waves

14 November 2011

The Optical Metrology Subsystem underwent its first full tests under space-like temperature and vacuum conditions using an almost complete version of the spacecraft.

The results exceeded the precision required to detect the enigmatic ripples in the fabric of space and time predicted by Albert Einstein - and did it by two to three times.

In space, LISA Pathfinder will measure the distance between two free-floating gold-platinum cubes using lasers. In the ground tests currently being performed by the team in Ottobrunn, Germany, these cubes are replaced by separate mirrors.

In addition to measuring the distance between the cubes, it also measures their angles with respect to the laser beams - and the tests show an accuracy of 10 billionths of a degree.

"This is equivalent to the angle subtended by an astronaut's footprint on the Moon!" notes Paul McNamara, Project Scientist for the LISA Pathfinder mission.

Under perfect conditions in space, the free-floating cubes would be expected to exactly copy each other's motions exactly.

However, according to Einstein's theory of General Relativity, if a gravitational wave were to pass through space, possibly caused by an event as catastrophic as the collision of two black holes, then a minuscule distortion in the fabric of space itself would be detectable.

The accuracy required to detect such a subtle change is phenomenal: around a hundredth the size of an atom - a picometre.

The requirement set for the instrument was around 6 picometres, measured over 1000 seconds, which the team initially bettered in 2010.

During the latest testing, a staggering 2 picometre accuracy was obtained, far exceeding the best performance for an instrument of this type.

"The whole team has worked extremely hard to make this measurement possible," said Dr McNamara.

"When LISA Pathfinder is launched and we're in the quiet environment of space some 1.5 million km from Earth, we expect that performance will be even better."

The instrument team from Astrium GmbH, the Albert Einstein Institute and ESA are testing the Optical Metrology Subsystem during LISA Pathfinder thermal vacuum tests in Ottobrunn by spacecraft prime contractor Astrium (UK) Ltd.

LISA Pathfinder is expected to be launched in mid-2014 to demonstrate the technologies and endurance in space for a New Gravitational wave Observatory mission, one of the candidates for ESA's next flagship mission, planned for a launch early in the next decade, aiming to find this final piece in Einstein's cosmic puzzle.

Notes for Editors

LISA Pathfinder is an ESA mission that aims to test several technologies in the LISA Technology Package for a future New Gravitational wave Observatory mission. LISA Pathfinder will demonstrate critical technologies of this future mission in a space environment, such as gravitational reference sensing, drag-free attitude control and interferometry with free-falling mirrors. Launch is scheduled for 2014 from Europe's Spaceport in French Guiana.

The measurements were made as part of the on-station thermal test campaign of the LISA Pathfinder flight system. The tests were performed at the Industrieanlagen-Betriebsgesellschaft mbH (IABG) facilities in Ottobrunn, Germany under the responsibility of the LPF Industrial prime contractor, Astrium Ltd, UK. The hardware for the Optical Metrology Subsystem was provided by: Tesat GmbH (laser); Contraves (laser modulator); Kaiser Threde (laser assembly); University of Glasgow (optical bench); University of Birmingham (phase meter); ICE (payload computer).

For further information, please contact:

Paul McNamara

LISA Pathfinder Project Scientist

Directorate of Science and Robotic Exploration, ESA, The Netherlands

Tel: +31 71 5658239

Email: Paul.McNamara esa.int



Markus Bauer

ESA Science and Robotic Exploration Communication Officer

Tel: +31 71 565 6799, +31 61 594 3 954

Email: markus.bauer esa.int

(This article was originally published on ESA's Space Science Portal.)