  For the first time in history, humans have reached the point where it is
possible to construct a revolutionary space-based observatory that has the
capability to find dozens of Earth-like worlds, and possibly some with signs of
life. This same telescope, designed as a long-lived facility, would also
produce transformational scientific advances in every area of astronomy and
astrophysics from black hole physics to galaxy formation, from star and planet
formation to the origins of the Solar System. The Association of Universities
for Research in Astronomy (AURA) commissioned a study on a next-generation
UVOIR space observatory with the highest possible scientific impact in the era
following JWST. This community-based study focuses on the future space-based
options for UV and optical astronomy that significantly advance our
understanding of the origin and evolution of the cosmos and the life within it.
The committee concludes that a space telescope equipped with a 12-meter class
primary mirror can find and characterize dozens of Earth-like planets and make
fundamental advances across nearly all fields of astrophysics. The concept is
called the High Definition Space Telescope (HDST). The telescope would be
located at the Sun-Earth L2 point and would cover a spectral range that, at a
minimum, runs from 0.1 to 2 microns. Unlike JWST, HDST will not need to operate
at cryogenic temperatures. HDST can be made to be serviceable on orbit but does
not require servicing to complete its primary scientific objectives. We present
the scientific and technical requirements for HDST and show that it could allow
us to determine whether or not life is common outside the Solar System. We do
not propose a specific design for such a telescope, but show that designing,
building and funding such a facility is feasible beginning in the next decade -
if the necessary strategic investments in technology begin now.
