Previous/Current Studies and Missions

Exoplanet studies to date can be divided into those from ground-based observatories and those from spacecraft.

Ground-based Observatories

The first exoplanet to be discovered orbiting a Sun-like star (51 Peg b) was discovered using the ELODIE spectrograph at the Observatoire de Haute-Provence (OHP).

Of course, many telescopes around the world have contributed to the discovery and confirmation of exoplanets. These include the Very Large Telescope in Chile, the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph on the 3.6 metre telescope at La Silla, Chile, as well as the Keck and Gemini telescopes in Hawai'i.

Additionally, there have been several dedicated surveys searching for exoplanets. These include:

WASP The Wide Angle Search for Planets discovered 118 exoplanets using the transit technique from their two observatory sites in South Africa and La Palma.
HAT The Hungarian Automated Telescope network is a set of 7 telescopes in Arizona, Australia, Namibia and Chile which has detected 61 exoplanets using the transit technique.

TrES The Trans-Atlantic Exoplanet Survey has three 10-cm telescopes in California, Arizona and Tenerife and has discovered 5 transiting exoplanets.
OGLE The Optical Gravitational Lensing Experiment is a Polish sky survey with several astronomical aims including the detection of microlensing and transiting exoplanets.
XO Located in Hawai'i, the XO telescopes have detected six transiting exoplanets.
KELT The Kilodegree Extremely Little Telescope features two telescopes in Arizona and South Africa and has discovered 15 transiting exoplanets around relatively bright and near stars.
NGTS Located at Paranal Observatory in Chile, the Next-Generation Transit Survey features an array of twelve 20-cm telescopes and has discovered one exoplanet system.
TRAPPiST The TRAnsiting Planets and Planetesimals Small Telescope has to date (November 2018) only discovered one exoplanet system, however it is perhaps the most famous and exciting system discovered. TRAPPIST-1 contains at least seven planets with three of them being Earth-sized.

Space-based Observatories

COROT Led by the French Space Agency in conjunction with ESA, COROT had the dual aims of detecting transiting exoplanets and performing astroseismology on nearby stars. Between 2007 and 2013, it discovered 32 exoplanets.
Kepler Retired in October 2018, NASA's Kepler and K2 missions revolutionised the discovery of transiting exoplanets with the detection of 2662 exoplanets.
Spitzer NASA's Spitzer Space Telescope observes in the infra-red and has multiple mission aims which include observing cool star-forming regions, galactic centres and exoplanetary systems and discs as well as brown dwarfs and giant molecular clouds. It provided the first ever direct detections of the exoplanets HD 209458b (aka Osiris) and TrES-1b.
Hubble The Hubble Space Telescope (HST) is perhaps the most famous telescope ever. Amongst its many discoveries, it has produced an image of the exoplanet, Fomalhaut b within a dust ring around its parent star, Fomalhaut, one of the brightest stars in the night sky found in the southern constellation of Piscis Austrinus.

Read more about future missions and projects.