The European Space Agency (ESA) have officially approved two space missions, LISA and EnVision, for launch in the 2030’s. LISA will search for gravitational waves whilst EnVision will study the interior and atmosphere of Venus. Both missions have contributions from NASA. The process of being formally `adopted’ by ESA can be a long drawn-out process. When I worked for UCL’s Mullard Space Science Laboratory from the mid 1990’s, I was part (in a small way) of its LISA development team. LISA then went through various name and design changes (which were later abandoned) and was eventually approved as a future mission in 2017. On 25th Jan 2024 it was officially adopted as an ESA mission which gives the go-ahead for the satellites and launcher to be built.
The Laser Interferometry Space Antenna (LISA) has the same design principals as the Earth ground based LIGO detectors which uses the principals of `interferometry’: as gravitational waves from merging black holes or neutron stars sweep past the gravitational wave observatories, it causes the laser beams to go out-of-sync by tiny amounts. It is the equivalent of measuring the distance to the nearest star to our Sun to within the diameter of a human hair. The beam length of the LIGO instruments is around 1600 km – for LISA they will be 2.5 million km — making this work successfully will be extraordinarily difficult. Indeed, before LISA was approved the LISA Pathfinder satellite – which had cost over-runs and technical challenges – had to be shown to work. When it eventually flew it vastly exceeded expectations.
Compared to LIGO, LISA will be sensitive to shorter frequency gravitational waves which are emitted from sources such as supermassive Blackholes at the center of galaxies and ultra-compact binary systems in our own Milky Way. I’ve been studying these binaries for ¼ of a century, and they are predicted to be the `verification’ sources for LISA: around ten known systems are expected to be detected in the first month of LISA observations. I’m one of the Affiliate Members of the LISA Consortium and LISA is expected to be launched in 2035 – around 35 years after I was first involved (in a very small way) in its development. A significant number of UK Universities and Labs are making important contributions to the success of LISA. Hopefully I will get to see first-hand the first results before I retire!
https://www.esa.int/Science_Exploration/Space_Science/Capturing_the_ripples_of_spacetime_LISA_gets_go-ahead
The EnVision satellite has the Earth’s near neighbour Venus as its target and will be aiming to determine why the Earth and Venus are now very different. The pressure on the surface of Venus is around 100 times as it is on Earth and can rain sulphuric acid. However, it’s possible that Venus was very different in the early years of the Solar system. Using radar instruments, EnVision will be able to probe the upper surface of Venus and using the Doppler signal of the spacecraft, map the planets gravitational field. It will also have three spectrometers which will be used to determine the composition of the atmosphere and surface of Venus. It is expected to be launched in the 2030’s.
https://www.esa.int/Science_Exploration/Space_Science/EnVision_factsheet
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