The Diffuse Intergalactic Oxygen Surveyor (DIOS) mission

The Diffuse Intergalactic Oxygen Surveyor (DIOS) mission is aimed
at conducting high sensitivity soft X-ray survey over a wide solid angle
of the sky and is designed based on the scientific goal of detecting
warm-hot intergalactic medium (WHIM). WHIM is important probe to
study large-scale structure of the universe formed by the dark matter
and can be traced by oxygen K-lines since the temperature of WHIM
is considered to be 105 - 107K. Goal of our mission is to perform
imaging-spectroscopy of OVII (561, 568, 574 eV) and OVIII(653 eV)
emission lines with 2 eV resolution to reveal spatial distribution of
WHIM in the red shift range of 0 < z < 0.3. The core instruments are
four-stage X-ray telescope FXT and the focal plain instrument XSA
(X-ray Spectrometer Array). Present status of the DIOS mission is
shown in this talk.