  MESS (Mass-loss of Evolved StarS) is a Guaranteed Time Key Program that uses
the PACS and SPIRE instruments on board the Herschel Space Observatory to
observe a representative sample of evolved stars, that include asymptotic giant
branch (AGB) and post-AGB stars, planetary nebulae and red supergiants, as well
as luminous blue variables, Wolf-Rayet stars and supernova remnants. In total,
of order 150 objects are observed in imaging and about 50 objects in
spectroscopy.
  This paper describes the target selection and target list, and the observing
strategy. Key science projects are described, and illustrated using results
obtained during Herschel's science demonstration phase.
  Aperture photometry is given for the 70 AGB and post-AGB stars observed up to
October 17, 2010, which constitutes the largest single uniform database of
far-IR and sub-mm fluxes for late-type stars.
