LISA adopted by ESA | In the Dark


I have some good news for gravitational-wave physicists to pass on. The European Space Agency (ESA) has formally “adopted” the Laser Interferometric Space Experiment (LISA) – a gravitational wave experiment in space. This follows the detection of gravitational waves using the ground-based experiment Advanced LIGO and the success of a space-based technology demonstrator mission called Lisa Pathfinder. LISA was actually selected as a potential mission in 2017 – see here – but “adoption” means that the mission concept and technology required are now both sufficiently advanced that it can proceed in 2025, once contractors are found to actually build it.

LISA consists of a flotilla of three spacecraft in orbit around the Sun forming the arms of an interferometer with baselines of the order of 2.5 million kilometres, much longer than the ~1km arms of Advanced LIGO. These larger dimensions make LISA much more sensitive to long-period signals. Each of the LISA spacecraft contains two telescopes, two lasers and two test masses, arranged in two optical assemblies pointed at the other two spacecraft. This forms Michelson-like interferometers, each centred on one of the spacecraft, with the platinum-gold test masses defining the ends of the arms.

Here’s an artist’s impression of LISA:

This is excellent news for the gravitational waves community, especially since LISA was threatened with the chop when NASA pulled out in 2011. Space experiments are huge projects – and LISA is more complicated than most – so it will take some time before it actually happens. The first I heard of the LISA concept was back in the mid-1990s and at the moment LISA is pencilled in for launch in 2035, so it will be forty years in the development.

Ireland is a full member of ESA so let’s hope the Irish Government finds a way of funding participation in the LISA mission. Although Ireland joined ESA nearly fifty years ago, and is paying  into the mandatory science programme which includes LISA (and, for example, Euclid), there is no funding programme in Ireland dedicated to the scientific exploitation of ESA projects. Let’s hope the Irish scientists involved in LISA – including those at Maynooth – are able to play a full part in this exciting project.

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