The science of EChO (Exoplanet Characterisation Observatory)

The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and ded-icated space missions has resulted in 700-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. Yet among the exoplanets detected or proposed, so far there is actually little resemblance to the morphology of the Solar System.
The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?

In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emis-sion spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.
The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different envi-ronments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.

EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates. Dr Giovanna Tinetti (UCL) has been selected as the ESA science team lead scientist for the assessment study phase, and Professor Bruce Swinyard (RAL/UCL) has been named as a member of the ESA science team. Our UK-led consortium has received full support from UKSA to complete the technical studies of the EChO payload. It is now paramount to secure the UK scientific return, and we estimate that a twenty-four months PDRA would provide Tinetti and Swinyard the needed support.

Maximising the return for the UK industry - our goal is to get UK industry as prime contractor for EChO or, at the very least, to be providing a significant part of the spacecraft system. The EChO mission requires some technological development, in particular of detectors, and we see major potential benefits to UK industry in developing solutions for EChO. We are working alongside UK industry to specify and assist in the development of those solutions to maximise the economic and technological return to the UK.

Outreach - The discovery of over 700 extrasolar planets in the last 15 years is probably the most exciting development of modern astronomy. It resonates enormously with a public that has already been shown to have high interest levels in the exploration of the diverse worlds of our own Solar System, and an insatiable hunger for news about space exploration. It directly addresses deep philosophical issues that concern our fellow citizens: what are other worlds like? how do they form and evolve? Are we alone in the universe? So that means that public outreach that aims to engage our fellow citizens with the excitement of EChO and its science objectives will be at the forefront of our planning.
We will also have a pro-active programme of briefing and informing policy makers at a national and European level, through one-on-one meetings, seminars for politicians, exhibitions at venues such as the European Parliament, and public events that will involve political figures as keynote speakers.

Attracting the Next Generation of Scientists and Engineers - the UK future economy and competitiveness depends on strong science and engineering sectors. The promotion of observational and space sciences is crucial to inspire development of the next generation of scientists and engineers. Extrasolar planets are today one of the most trendy subject, inspiring young people to take up the (physical) sciences in later studies and in their careers.