page_title: ESPRESSO
section_title: Instrument
hierarchical_section_title: ESPRESSO / Instrument
caption_attribution_description: English: The ESPRESSO instrument on ESO’s Very Large Telescope in Chile has used the combined light of all four of the 8.2-metre Unit Telescopes for the first time. Combining light from the Unit Telescopes in this way makes the VLT the largest optical telescope in existence in terms of collecting area. This picture shows in highly simplified form how the light collected by all four VLT Unit Telescopes is combined in the ESPRESSO instrument, located under the VLT platform.
context_page_description: ESPRESSO is a third-generation, fiber fed, cross-dispersed, echelle spectrograph mounted on the European Southern Observatory's Very Large Telescope. The unit saw its first light on September 25, 2016.
  ESPRESSO is the successor of a line of echelle spectrometers that include CORAVEL, Elodie, Coralie, and HARPS. It measures changes in the light spectrum with great sensitivity, and is being used to search for Earth-size rocky exoplanets via the radial velocity method. For example, Earth induces a radial-velocity variation of 9 cm/s on the Sun; this gravitational "wobble" causes minute variations in the color of sunlight, invisible to the human eye but detectable by the instrument. The telescope light is fed to the instrument, located in the VLT Combined-Coude Laboratory 70 meters away from the telescope, where the light from up to four unit telescopes of the VLT can be combined. The Principal Investigator is Francesco Pepe.
context_section_description: For calibration, ESPRESSO uses a laser frequency comb (LFC), with backup of two ThAr lamps. It features three instrumental modes: singleHR, singleUHR and multiMR. In the singleHR mode ESPRESSO can be fed by any of the four UTs.
caption: First light of the ESPRESSO instrument with all four unit telescopes[11]
exif: {"Image ImageDescription": "The ESPRESSO instrument on ESO\u2019s Very Large Telescope in Chile has used the combined light of all four of the 8.2-metre Unit Telescopes for the first time. Combining light from the Unit Telescopes in this way makes the VLT the largest optical telescope in existence in terms of collecting area. This picture shows in highly simplified form how the light collected by all four VLT Unit Telescopes is combined in the ESPRESSO instrument, located under the VLT platform."}