A Cryogenic Space Telescope for Far-Infrared Astrophysics: A Vision for
  NASA in the 2020 Decade
  Many of the transformative processes in the Universe have taken place in
regions obscured by dust, and are best studied with far-IR spectroscopy. We
present the Cryogenic-Aperture Large Infrared-Submillimeter Telescope
Observatory (CALISTO), a 5-meter class, space-borne telescope actively cooled
to 4 K, emphasizing moderate-resolution spectroscopy in the crucial 35 to 600
micron band. CALISTO will enable NASA and the world to study the rise of heavy
elements in the Universe's first billion years, chart star formation and black
hole growth in dust-obscured galaxies through cosmic time, and conduct a census
of forming planetary systems in our region of the Galaxy. CALISTO will
capitalize on rapid progress in both format and sensitivity of far-IR
detectors. Arrays with a total count of a few 100,000 detector pixels will form
the heart of a suite of imaging spectrometers in which each detector reaches
the photon background limit.
  This document contains a large overview paper on CALISTO, as well as six 2-3
page scientific white papers, all prepared in response to NASA's Cosmic Origins
Program Analysis Group (COPAG's) request for input on future mission concepts.
  The Far-IR Science Interest Group will meet from 3-5 June 2015 with the
intention of reaching consensus on the architecture for the Far-IR Surveyor
mission. This white paper describes one of the architectures to be considered
by the community. One or more companion papers will describe alternative
architectures.
