As set out in its convention, ESO provides state of the art facilities for Europe's astronomers and promotes and organises cooperation in astronomical research. Today, ESO operates some of the world's largest and most advanced observational facilities at three sites in Northern Chile: La Silla, Paranal and Chajnantor. These are the best locations known in the southern hemisphere for astronomical observations. With other activities such as technology development, conferences and educational projects, ESO also plays a decisive role in forming a European Research Area for astronomy and astrophysics.
| Name | Size | Type |
| Very Large Telescope (VLT) | 4 x 8.2 m + 4 x 1.8 m | optical, near- and mid-infrared telescope array |
| New Technology Telescope (NTT) | 3.58 m | optical and infrared telescope |
| ESO 3.6-metre telescope | 3.57 m | optical and infrared telescope |
| MPG/ESO 2.2-metre telescope 2.2 m | 2.20 m | optical and infrared telescope |
| Atacama Pathfinder Experiment (APEX) | 12 m | millimetre-/submillimetre-wavelength telescope |
| Atacama Large Millimeter/submillimeter Array (ALMA) | 50 x 12 m, and 12 x 7 m + 4 x 12 m (ACA) | millimetre-/submillimetre-wavelength interferometer array telescope |
| Visible and Infrared Survey Telescope for Astronomy (VISTA) | 4.1 m | near-infrared survey telescope |
| VLT Survey Telescope (VST) | 2.6 m | optical survey telescope |
European Extremely Large Telescope (E-ELT) |
42 m | optical to mid-infrared telescope |
Paranal Observatory Instrumentation
The Very Large Telescope (VLT) at Cerro Paranal is ESO's premier site for observations in the visible and infrared light. All four unit telescopes of 8.2m diameter are individually in operation with a large collection of instruments.
The VLT offers also the possibility of combining the light from the four UTs to work as an interferometer. The Very Large Telescope Interferometer (VLTI), with its own suite of instruments, ultimately providing imagery at the milli-arcsecond level as well as astrometry at 10 micro arcsecond precision. In addition to the 8.2m diameter telescopes the VLTI is complemented with four Auxiliary Telescopes (AT) of 1.8m diameter to improve its imaging capabilities and enable full nighttime use on a year-round basis.
Two telescopes for imaging surveys are complementing the VLT on Paranal, the VLT Survey Telescope (VST, 2.6m diameter, in construction) for the visible, and the Visible and Infrared Survey Telescope for Astronomy (VISTA, 4m).
See the VLT on Google Maps and with pictures from the public.
La Silla Observatory Instrumentation
ESO operates three major telescopes (3.6m telescope, New Technology Telescope (NTT), 2.2m Max-Planck-ESO telescope) at the La Silla Observatory. They are equipped with state of the art instruments either built completely by ESO or by external consortia, with substantial contribution by ESO.
See La Silla on Google Maps and with pictures from the public.
APEX
APEX, the Atacama Pathfinder Experiment, is a collaboration between Max Planck Institut für Radioastronomie (MPIfR) at 50%, Onsala Space Observatory (OSO) at 23%, and the European Organisation for Astronomical Reseach in the Southern Hemiphere (ESO) at 27% to construct and operate a modified ALMA prototype antenna as a single dish on the 5100 m high site of Llano Chajnantor. The telescope was supplied by VERTEX Antennentechnik in Duisburg, Germany. APEX has a suite of heterodyne spectrometers and wide-field bolometer cameras operating in most of the atmospheric windows from 0.2 to 1.4 mm.
See the Chajnantor site in Google Maps with images from the public.
ALMA
The Atacama Large Millimeter Array, or ALMA, is an international collaboration to develop a world-class telescope array to study the universe from a site in the foothills of Chile's Andes Mountains. Each of ALMA's antenna dishes will measure 12 meter wide. The ALMA antennas will be movable. At its largest, the array will measure 16 km, and at its smallest, only 150 m. Its receivers will cover the range from 30 to 950 GHz. The ALMA correlator, a specialized computer that combines the information received by the antennas, will perform an astounding 16,000 million-million (1.6x1016) operations per second.
An additional, compact array of 7m and 12m diameter antennas is also foreseen. Construction of ALMA started in 2003 and will be completed in 2012; it will become incrementally operational from 2011 on.
For more information please read the ALMA page.
E-ELT
ESO has been working together with its user community of European astronomers and astrophysicists to define the new giant telescope needed by the middle of the next decade. More than one hundred astronomers from all European countries have been involved throughout 2006, helping the ESO Project Offices to produce a novel concept, in which performance, cost, schedule and risk were carefully evaluated.
The present concept features as a baseline a telescope with a 42m diameter mirror, and is revolutionary. The site of the E-ELT is not yet fixed as studies are still underway with a plan to make a decision by 2008.
With a diameter of 42 m and its adaptive optics concept, the E-ELT will be more than one hundred times more sensitive than the present-day largest optical telescopes, such as the 10-m Keck telescopes or the 8.2-m VLT telescopes.
For more information please read the E-ELT page.