ESPRESSO: a new spectrograph for the VLT (part III) - on Coudé Train (ESPRESSO III)

FCOMP-01-0124-FEDER-019884 & PTDC/CTE-AST/120251/2010

Principal investigator
Nuno C. Santos

Following the guidelines already presented and discussed with FCT, the present project is a component (part III) of the planned Portuguese support for the national participation in the project of a new high resolution super-stable spectrograph for the European Southern Observatory (ESO) Very Large Telescope (VLT): ESPRESSO. It will focus on the construction of one of the 4 'coudé trains' of the instrument.

A first already funded project (started in 2010)covers the activities of the first phases (it does not include funds for hardware). Another project (part II) is also now submitted to build a second component of the 'Coudé Train: the Atmospheric Dispersion Corrector (ADC). None of the projects is coincident in time.

The development of different high resolution spectrographs over the last years allowed a considerable development of a number of different domains in Astrophysics. Areas such as the detection of exoplanets, the study of stellar of stellar oscillations, the discovery that the fundamental constants of physics may have varied in the past, or the analysis of chemical abundances and isotopic ratios in distant stars, have seen an unprecedented success. New questions have been raised, and new solutions are being sought.

Motivated by these premises, a new generation of instruments and telescopes is being conceived by different teams around the world. This includes a new generation of Extremely Large Telescopes (ELTs). In parallel, a number of new instruments for current 8 to 10-m class facilities is being planned.

With this in mind, ESO opened in March 2008 a cal-for-proposals to build a new high-resolution ultra stable spectrograph for the VLT. In reply to this call a consortium was created that includes the Centro de Astrofísica da Universidade do Porto (leader of the national consortium also including SIM and CAAUL from Faculdade de Ciências da Universidade de Lisboa), the Geneva Observatory and the Physics Institute/University of Bern (Switzerland), the Instituto de Astrofisica de Canarias (Spain), the Trieste and Brera Observatories/INAF  (Italy), and ESO. The project was named ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations). The PI of the present project and leader of the national team (N. Santos) is one of the 4 Co-PIs of the consortium.

The co0nsortium proposed to ESO the construction of a high-efficiency, high-resolution, fiber-fed spectrograph of high mechanical and thermal stability located at the VLT incoherent Coudé Focus (Pepe et al. 2010). The goal is to combine and improved the stability of instruments like HARPS with the efficiency of UVES ( http://www.eso.org/sci/facilities). ESPRESSO is an innovative instrument to fully exploit the VLT potentiality. In particular, it will offer the possibility of combining the light of the 4 VLT-Unit Telescopes, making of it the first 16-m equivalent telescope in the world, several years before the E-ELT is available to the community.

This project has been accepted by ESO for Phase A study in January 2009, a phase completed later that year. In March 2010 it was successfully reviewed by an independent board nominated by ESO, and approved for construction by the ESO Council in June 2010. The detailed design phase is now starting, and the procurement and construction of the hardware components will initiate in 2012. If there are no major difficulties, this spectrograph will be mounted at the VLT site in 2016.

The unprecedented precision in the radial velocities determination together with the largest photon collecting area will certainly provide breakthroughs in many areas of astronomical research (as those mentioned above). Particular attention should be given to the two main science cases of ESPRESSO: the search for Earth-like planets, and the measurement of the variation of physics fundamental constants. ESPRESSO will change our current knowledge in these two high impact domains.

The proposed Portuguese participation in ESPRESSO is in this respect crucial. On the one side, all the scientific areas mentioned above are particularly fond to the national astronomical community. This is particularly true to some of our team members, that have a strong international recognition for their research. Furthermore, and based on the previous successful experience of our team with other ESO instrumentation, in the context of the ESPRESSO project our team is responsible for the design and construction of the 'Coude Train' for the VLT (Cabral et al. 2010). This key component will bring the light from the 4 UT telescopes to the Combined Coude Room, where the instrument will be positioned.

The goal of the present is to give to the national team the necessary means to continue its participation in this (scientifically) ambitious project, namely by enabling the construction of one specific hardware part that is of responsibility of the national consortium: one of the 4 Coudé Trains.

Institutions & Research Units involved in the project:
- Centro de Astrofísica da Universidade do Porto (CAUP/UP)
- Fundação da Faculdade de Ciências da Universidade de Lisboa (FFC/FC/UL)
- Centro de Astronomia e Astrofísica (CAA/FC/UL)

Funding institution
Fundação para a Ciência e a Tecnologia

Start: 1 January 2013
End: 28 February 2014