Technology test for detection of gravitational waves

Space probe LISA Pathfinder with experiments for a better understanding of the relativity theory is ready to start

The space probe LISA Pathfinder (artistic illustration) serves as a test for important technologies for the direct detection of gravitational waves. © ESA / ATG medialab
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The search for gravitational waves continues: In just a few days, the space probe LISA Pathfinder, which will test important technologies for detecting the elusive waves, will be launched. The systems of the probe can measure distances to a millionth of the thickness of a hair exactly and shield their experiments against all external disturbances. If this test succeeds, this is an important step towards a space observatory for gravitational waves.

Gravitational waves are something of a sacred grail of astrophysics: Einstein's theory of general relativity predicts that they must exist, yet no one has yet observed them. Huge cosmic events like blurring black holes or stellar explosions, according to theory, make space-time ripples, much like a pebble thrown into a pond sends waves across the surface of the water. However, such gravitational waves are so far only indirectly detectable. So far, detectors on Earth that compare the transit times of laser pulses over hundreds of meters and directly measure the smallest deformations of space-time have not been successful so far.

Tiny distortions of space-time

As the gravitational force and the magnetic field of the earth make the direct detection of gravitational waves difficult, the ESA space probe LISA Pathfinder in space is now to help. With the technology on board the probe, scientists want to first find out if such a proof is technically feasible: "These tiny distortions of space-time require a very sensitive and high-precision measuring technology whose performance can only be tested in outer space free from external disturbances, " says François Auque from the developer Airbus Defense and Space.

The LISA technology package consists of a laser interferometer and two high-precision, 1.96 kg cubes made of a gold-platinum alloy. The cubes serve as test masses, while the interferometer measures the distance between them in unprecedented accuracy. The device is intended to detect differences in the picometer range, less than one millionth of the thickness of a human hair.

The special feature is that the two cubes will float freely at a distance of about 40 centimeters during the experiment, as soon as they are released from their brackets. Free of any disturbing factors they are then in free fall, which is influenced exclusively by gravity. display

Completely new view of the universe

For this purpose, the scientists are also testing two different microdrives on board the probe. Each of these engines is so weak that it could barely prevent a snowflake from sinking. For example, LISA Pathfinder uses these drives to counteract solar radiation and compensate for disturbing movements from the outside, so that the movement of the test cube remains unaffected.

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Background of the LISA Pathfinder Mission ESA

If all this technology works flawlessly, LISA-Pathfinder may pave the way for new research methods: Previous telescopes use almost exclusively electromagnetic waves of various wavelengths, from radio waves to X-rays. A space observatory using gravitational waves could therefore provide a completely new view of the universe. The plan is to create an ensemble of three space probes that form a huge triangle and determine their positions with the utmost precision using lasers.

Spacecraft launch for early risers

The launch of the nearly two-tonne probe from the ESA Kourou spaceport in French Guiana is scheduled for December 2, 2015 at 5:15 am Central European Time. After several correction maneuvers, LISA Pathfinder will reach its final destination towards the end of January 2016, the first Lagrange point between Earth and Sun. The scientific experiments take place at a distance of 500, 000 to 800, 000 kilometers in an orbit around this point.

Interested early risers can follow the launch live: ESA will set up a livestream and comment on the launch via the Twitter accounts @esaoperations, @ESA_LPF and @ESA under the hashtag #LISAPathfinder.

(ESA / Airbus, 30.11.2015 - AKR)