CHES: a space-borne astrometric mission for the detection of habitable
  planets of the nearby solar-type stars
  The Closeby Habitable Exoplanet Survey (CHES) mission is proposed to discover
habitable-zone Earth-like planets of the nearby solar-type stars (~10pc away
from our solar system) via micro-arcsecond relative astrometry. The major
scientific goals of this mission are: to search for Earth Twins or the
terrestrial planets in habitable zones orbiting 100 FGK nearby stars; further
to conduct a comprehensive survey and extensively characterize the nearby
planetary systems.
  CHES will offer the first direct measurements of true masses and inclinations
of Earth Twins and super-Earths orbiting our neighbor stars based on
micro-arcsecond astrometry from space. This will definitely enhance our
understanding of the formation of diverse nearby planetary systems and the
emergence of other worlds for solar-type stars, and finally to reflect the
evolution of our own solar system.
  The primary payload is a high-quality mirror with a diameter of 1.2 m, a FOV
of 0.44{\deg} x 0.44{\deg}. The coaxial three-reflection TMA system is
designed, along with Mosaic CCDs and the laser metrology technique, to archive
1 {\mu}as astrometric precision at 500nm~900nm. CHES satellite operates at the
Sun-Earth L2 point and observes the entire target stars for 5 years.
  CHES will produce fruitful achievements not only in the Earth-like planets
but also for cosmology, dark matter and black holes, which helps us better
understand the philosophy, life and planet.
