ESPRESSO

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.

ESPRESSO builds on the foundations laid by the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument at the 3.6-metre telescope at ESO's La Silla Observatory.

ESPRESSO benefits not only from the much larger combined light-collecting capacity of the four 8.2-metre VLT Unit Telescopes, but also from improvements in the stability and calibration accuracy that are now possible by laser frequency comb technology.

[citation needed] The ESPRESSO would greatly exceed this capability making detection of Earth-size planets from ground-based instruments possible.

And so, some fine-tuning, including replacing the parts causing the efficiency problem and subsequent re-testing, were to be done on the instrument before the full 4-UT mode was open to the scientific community in April 2019.

[22][needs update] A problem was discovered in the ESPRESSO charge-coupled device controllers, digital imaging hardware, where a differential nonlinearity issue has reduced the resolution obtainable more severely than was previously feared.

The ESO detector team that determined the source of the problem is currently, as of June 2019,[update] working on a new version of the associated hardware in order to remedy this hopefully temporary setback.

[25] Due to the limited spectral coverage and lack of reliability, the Laser Frequency Comb (LFC) is currently not integrated into the telescope and for now complete wavelength calibration will have to rely on the two backup ThAr lamps, with resultant radial velocity measurements values limited by photon noise, stellar jitter and so less precise than expected.

[27][28] On August 28, 2020, it was announced that in the coming weeks minimal science operations are planned to be resumed at the Paranal Observatory, following after a 5-month suspension due to the COVID-19 pandemic.