ESPRESSO Science Verification


General Information

An integral part of the commissioning of a new instrument at the VLT is the Science Verification phase. SV programmes include a set of typical scientific observations that should verify and demonstrate to the community the capabilities of the new instrument in the operational framework of the VLT Observatory. In accordance with its SV Policy and Procedures  ESO encourages the community to submit also highly challenging or risky science observations that will push ESPRESSO in its 4-UT modes to its limits in order to better understand the instrument and mode performance parameter spaces and their envelopes.  

The Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO), is a super-stable Optical High Resolution Spectrograph for the combined coudé focus of the VLT. It can be operated by either one of the UTs or collecting the light from up to 4 UTs simultaneously.

ESPRESSO is now offered to the community for Science Verification (SV) for 2 nights in August 2019. All astronomers are invited to participate in this opportunity to obtain unique science with the 4-UT ESPRESSO mode and thus to demonstrate its scientific capabilities. A call for proposals has been issued and the community is invited to submit proposals for the ESPRESSO science verification using the simplified proposal template.

The deadline for proposal submission is 5 July 2019, 18:00 CEST.

Proposals will be reviewed by an internal panel and allocated time on the basis of scientific merit and feasibility, as well as in the demonstrated ability of the Principle Investigators to deliver results on a timely basis.

The observations will be conducted during the nights of 26/27 August 2019 in Service Mode by a dedicated team of ESO astronomers. The ESPRESSO SV team will be able to assist the successful PI’s in the preparation and optimisation of the OBs.

The ESPRESSO ETC has been updated for the new mode, but may still change as the commissioning is still ongoing.

The latest version of the ESPRESSO data reduction pipeline will be available for reduction of the SV data. Proposers are reminded that all SV data are made public worldwide immediately after passing the usual quality control checks.

Short description of ESPRESSO

ESPRESSO is the ESO/VLT high-resolution spectrograph for measuring precise radial velocities on a long timespan with the main scientific objectives of detecting and characterising Earth twins in the habitable zone of solar-like stars and of measuring the variations of fundamental physical constants in the Universe through accurate wavelength measurements.

ESPRESSO is a highly-stabilized fibre-fed échelle spectrograph that can be fed with light from either one or the four Unit Telescopes of the VLT. The instrument is installed at the incoherent combined Coudé focus (ICCF) of the VLT. The light from the astronomical source is redirected from the telescopes to the detectors through three components of the ICCF facility: the Coudé trains, the front ends, and the spectrograph. The Coudé Trains (CT) bring the light from each telescope to the Combined Coudé Lab (CCL) through 13 optical elements, including mirrors, lenses, and prisms. The four Front Ends (one for each UT) receive the light from the CTs and feed the entrance fibres. The Fibre Link transports the light from the Front Ends to the vacuum vessel. The latter is thermally stabilized at the mK level and pressure stabilized at the mbar level. The light then goes through the different optical elements of the spectrograph and is split into a red and a blue spectrum that are recorded by the corresponding red and blue cameras.

The spectrograph is fed by two fibres, one for the target itself and the other for simultaneous calibration (either sky or simultaneous reference: Laser Frequency Comb, Fabry-Perot or Thorium-Argon lamp). The light from the two fibres is recorded onto a blue (380-520nm) and a red (520-775nm) detector. The instrument can operate in three different modes: High Resolution 1UT (HR), Ultra High-Resolution 1UT (UHR), and Medium Resolution 4UTs (MR). The main characteristics of these modes are summarised below (for more information about the characteristics of the instrument, see the Instrument Description). The SV now released is only for the 4-UT mode, which can only be operated in the MR mode.

Phase 2 preparation

The PIs (or their Phase 2 delegates) of accepted proposals must prepare and submit the Phase 2 material using P2 

by 31 July 2019, 12:00 Central European Time (CEST)

to ensure that all observing material can be verified and is ready for the observations during the SV run during the 26 and 27 of August 2019.

The service mode guidelines for preparing the SV observations are the same as those for regular ESPRESSO observations, available at, with the following differences:

  • For SV observations, ESPRESSO is only offered in the 4-UT multiMR mode in service mode
  • As the multi-MR mode is intended for faint sources, normally SKY should be used as the Source on fiber B
  • We strongly encourage you to specify a telescope guide star to make sure that the same guide star is used for all 4 telescopes. The selection of a suitable guide star is supported by  the 'ObsPrep' tool in p2.


Approved programmes

A total of 10 proposals have been allocated SV time. The observations were performed in Service Mode style by a dedicated team and the collected data is made available to the whole user community through the ESO Archive. See VLT SV Policy and Procedures for more details.

Due to inclement weather conditions not all programmes could be observed.

All (raw) data for the respective programmes will be available by following the link that will be posted in the STATUS column in the table below.
There is no proprietary period nor earlier data release to the PIs.

Pipeline-reduced data is made available in the links provided below. The vanilla pipeline recipe was run. The users should assert themselves that the reduced data can be used for their science case. Individual data reductions may be required for some cases.

Programme ID

PI Name Project title Status Pipeline
Reduced data
60.A-9502(A) Groh Unstable massive stars in metal-poor dwarf galaxies COMPLETED Available
60.A-9503(A) Opitom Detecting water outgassing in the main asteroid belt COMPLETED Available
60.A-9504(A) Allart A mini-Neptune atmosphere through the eyes of the largest telescope Not started  
60.A-9505(A) Pasquini Chemical composition of an extragalactic Globular Cluster turnoff star COMPLETED Available
60.A-9506(A) Webb A high-precision fine-structure constant from a new absorber COMPLETED Available
60.A-9507(A) Vanzella Lasing ESPRESSO with a Cosmological LASER COMPLETED Available
60.A-9508(A) Cooke Identifying the isotopes made by the first stars COMPLETED Available
60.A-9509(A) Bonifacio 6Li (and 6Li/7Li ratio) in the SMC COMPLETED Available
60.A-9510(A) Braga Setting the Galactic clock with ESPRESSO Not started  
60.A-9511(A) Prudil The impact of shock on the atmosphere of RR Lyrae stars Not started  

Useful links