The ESO Diffuse Interstellar Bands Large Exploration Survey: EDIBLES I.
  Project description, survey sample and quality assessment
  The carriers of the diffuse interstellar bands (DIBs) are largely
unidentified molecules ubiquitously present in the interstellar medium (ISM).
After decades of study, two strong and possibly three weak near-infrared DIBs
have recently been attributed to the C60+ fullerene based on observational and
laboratory measurements. There is great promise for the identification of the
over 400 other known DIBs, as this result could provide chemical hints towards
other possible carriers.
  In an effort to systematically study the properties of the DIB carriers, we
have initiated a new large-scale observational survey: the ESO Diffuse
Interstellar Bands Large Exploration Survey (EDIBLES). The main objective is to
build on and extend existing DIB surveys to make a major step forward in
characterising the physical and chemical conditions for a statistically
significant sample of interstellar lines-of-sight, with the goal to
reverse-engineer key molecular properties of the DIB carriers.
  EDIBLES is a filler Large Programme using the Ultraviolet and Visual Echelle
Spectrograph at the Very Large Telescope at Paranal, Chile. It is designed to
provide an observationally unbiased view of the presence and behaviour of the
DIBs towards early-spectral-type stars whose lines-of-sight probe the
diffuse-to-translucent ISM. Such a complete dataset will provide a deep census
of the atomic and molecular content, physical conditions, chemical abundances
and elemental depletion levels for each sightline. Achieving these goals
requires a homogeneous set of high-quality data in terms of resolution (R ~
70000 -- 100000), sensitivity (S/N up to 1000 per resolution element), and
spectral coverage (305--1042 nm), as well as a large sample size (100+
sightlines). In this first paper the goals, objectives and methodology of the
EDIBLES programme are described and an initial assessment of the data is
provided.
