  The upcoming launch of the James Webb Space Telescope (JWST) combined with
the unique features of the TRAPPIST-1 planetary system should enable the young
field of exoplanetology to enter into the realm of temperate Earth-sized
worlds. Indeed, the proximity of the system (12pc) and the small size (0.12
Rsun) and luminosity (0.05 Lsun) of its host star should make the comparative
atmospheric characterization of its seven transiting planets within reach of an
ambitious JWST program. Given the limited lifetime of JWST, the ecliptic
location of the star that limits its visibility to 100d per year, the large
number of observational time required by this study, and the numerous
observational and theoretical challenges awaiting it, its full success will
critically depend on a large level of coordination between the involved teams
and on the support of a large community. In this context, we present here a
community initiative aiming to develop a well-defined sequential structure for
the study of the system with JWST and to coordinate on every aspect of its
preparation and implementation, both on the observational (e.g. study of the
instrumental limitations, data analysis techniques, complementary space-based
and ground-based observations) and theoretical levels (e.g. model developments
and comparison, retrieval techniques, inferences). Depending on the outcome of
the first phase of JWST observations of the planets, this initiative could
become the seed of a major JWST Legacy Program devoted to the study of
TRAPPIST-1.
