ESO Search for Potential Astronomical Sites
Working Group Terms of Reference
The site survey for the VLT ended in 1990 with the choice of Cerro Paranal based on the conclusions
of the VLT Site Selection Working Group (VLT Report 62, Nov. 90, Ed. M. Sarazin).
ESO initiated a site survey of the Namibian site of Gamsberg in 1994 as a preventive
action during the conflict about the ownership of the land around the VLT site of Paranal in Chile.
The creation of a first Working Group on Alternative Sites was decided by ESO Council
during its April 19, 1995 meeting, with the task of proposing alternatives for
the possible placement of one VLT telescope or the entire VLT/VLTI (ESO/Cou-549).
The working group named ESPAS-1995 met once in Spring 1996 and produced a list of sites, along with
a recommendation to further investigate the potentialities of Mt. Maidanak in Uzbekistan.
1997 to 1999, ESO and Tashkent Observatory, associated to Moscow Sternberg Institute and Nice University,
conducted a 2 years long site survey with funds from the European program INTAS, which resulted
in a full characterization of Maidanak with the same instrumentation as previously used in Chile.
In 1998, ESO has started a Concept Study for the next generation of ground-based
Extremely Large Telescopes (ELTs). This became the Overwhelmingly Large Telescope (OWL)
project which obtained support from the ESO Scientific and Technical Committee (STC).
In a high level meeting in March 2000, ESO and AURA (Association of Universities for Research in Astronomy, Inc., USA) agreed to establish a close "informal" collaboration on
ELT studies, in the form of 6 joint AURA-ESO
Working Groups (WGs). ESPAS-2000 is the ESO side of ELT-WG6 (site characterization).
Site characterization for Extremely Large Telescopes (ELT)
1- Earth-wide search for promising sites: an analysis of the characteristics which make a site suited for
astronomy with ELTs, on the basis of criteria extracted from
existing observatories, so as to proceed to a global identification of the
2- Long-term climate variability study in Chile: a study of the climate variability in northern chile based on the astroclimatic records of ESO
sites to be later pursued on the candidate sites determined in (1). The idea is to be able
to determine the phase of the climatic cycle of the candidate sites so as to shorten the
duration of the field monitoring.
3- Definition of the instrumentation required for monitoring the parameters defined in (1)
4- Characterization of the scientific merit of the parameters defined in (1) for various science
June 5, 2000