Past, present and future exoplanet missions
CHEOPS isn’t the first space telescope studying other worlds, nor will it be the last
MOST Launch date: 2003 End date: 2019
The Microvariability and Oscillations of Stars mission was Canada’s first space telescope and one of the earliest spacebased exoplanet hunters. It was also quite small, picking up the nickname ‘the Humble Space Telescope’. In 2011 it detected transits of the star 55 Cancri A by an exoplanet – up to five are now thought to orbit the star.
Kepler Launch date: 2009 End date: 2018
A telescope specifically designed to detect planets around other stars, Kepler is notable for promising much, but massively over-delivering on its mission. Originally planned to last 3.5 years, Kepler eventually ran out of fuel nine years and seven months after launch, having observed 530,506 stars and discovering 2,662 planets.
Gaia Launch date: 2013
End date: 2022 to 2024
An ESA mission aiming to collect the largest astronomical catalogue yet, Gaia is targeting around one per cent of stars in the Milky Way, all above magnitude 20, of which it will make a precise 3D map. It is also expected to discover quasars and exoplanets outside our Solar System, and new asteroids and comets within it.
ASTERIA Launch date: 2017 End date: Unknown
The Arcsecond Space Telescope Enabling Research in Astrophysics is a tiny technology demonstrator from NASA that may become part of a swarm of cubesats monitoring multiple targets at once for longer periods, also identifying new targets for other telescopes to observe. It is currently searching for exoplanets around nearby bright stars.
TESS Launch date: 2018 End date: Planned for 2020
The Transiting Exoplanet Survey Satellite is a NASA mission searching for exoplanets in an area 4,000-times larger than that covered by Kepler. TESS almost immediately found a new comet after beginning its observations and discovered its first exoplanet after less than two months, a super-Earth orbiting the yellow dwarf Pi Mensae.
JWST Launch date: Planned for 2021 End date: Five-year design life
Hubble’s successor, the JWST will use its mirror to observe in wavelengths ranging from long visible light to the midinfrared, meaning it can see high-redshift objects that are very old. Exoplanet hunting is also part of its brief, using a direct imaging technique rather than photometry. This works best on planets that emit infrared light.
ARIEL Launch date: 2028 End date: Four-year mission plan
The Atmospheric Remote-sensing Infrared Exoplanet Large-survey is an ESA telescope that will observe 1,000 planets orbiting distant stars and make a survey of their chemistry. It will carry a reflecting telescope and a spectrometer to detect the chemical fingerprints of gases in the planets’ atmospheres. It will focus on warm planets orbiting close to their stars.
Darwin Launch date: Proposed in 1993 End date: Cancelled in 2007
A set of three free-flying space telescopes positioned beyond the Moon, Darwin was a proposed ESA mission to observe extrasolar planets and produce very highresolution infrared images at least ten-times more detailed than the JWST’s. While Darwin never took off, both the ESA and NASA have considered similar missions since.