Optical bench survives 35G in readiness for space launch

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High-precision lasers are central to a proposed space launch designed to measure gravitational waves.

Scientists at the University of Glasgow’s Institute for Gravitational Research (IGR) say they have successfully reached another important milestone and look firmly on course for a launch in 2015. Its heart, the optical bench, has now been further integrated into the core assembly of the satellite.

The optical bench of the LISA Pathfinder (LPF) mission is the heart of a technology demonstrator mission that researchers say will pave the way for a future spaceborne detector to measure gravitational waves. These ripples in space-time are caused by massively violent astronomical events such as the collision of black holes and the explosion of dying stars.

The IGR team in the School of Physics and Astronomy demonstrated that the high-precision sensor system is ready to survive tremendous forces of up to 35 times the gravitational acceleration on Earth during rocket launch, and still maintain its precise alignment.

Dr Christian Killow, Scottish universities physics alliance advanced fellow at the university, said: 'With the optical bench now in place, we have reached an important milestone. The sophisticated laser interferometer performs superbly and is ready for its job in space. We are really excited that the LISA Pathfinder mission is now well positioned for launch in 2015.'

LISA Pathfinder is a European Space Agency (ESA) technology test mission that aims to prove essential key technologies for future space-based gravitational-wave observatories, which cannot be tested on Earth, but only in space.

For this purpose, one laser arm of a planned large gravitational wave mission is reduced from millions of kilometres to 40cm to fit into a single spacecraft. The optical bench tested at the IGR in Glasgow is the heart of LPF.

It is now in Astrium, Germany, and on course for a launch in 2015. At Astrium, members of the Glasgow team performed health checks on the optical bench photodiodes that turn the laser beams into electrical signals, and also micron-level measurement of the beam positions on the photodiodes – a very strong indicator that the bench survived transit unchanged.

LISA Pathfinder is paving the way for a large-scale space mission designed to detect one of the most elusive phenomena in astronomy – gravitational waves. Extreme precision is required to detect the tiny ripples in the fabric of space and time predicted by Albert Einstein. A direct detection of gravitational waves will add a new sense to our perception of the Universe: for the first time researchers will be able to ‘listen’ to the Universe, as gravitational waves are in some respects similar to sound waves. Hence gravitational wave astronomy will complement our understanding of the Universe and its evolution.

Gravitational waves measured by a large mission in space will allow scientists to trace the formation, growth, and merger history of massive black holes. It will also enable scientists to test General Relativity with observations, and will probe new physics and cosmology.