The Milky Way Imaging Scroll Painting (MWISP): Project Details and
  Initial Results from the Galactic Longitude of 25.8deg to 49.7deg
  The Milky Way Imaging Scroll Painting (MWISP) project is an unbiased Galactic
plane CO survey for mapping regions of l=-10deg to +250deg and |b|<5.2deg with
the 13.7 m telescope of the Purple Mountain Observatory. The legacy survey aims
to observe the 12CO, 13CO, and C18O (J=1-0) lines simultaneously with full
sampling using the nine-beam Superconducting SpectroScopic Array Receiver
(SSAR) system with an instantaneous bandwidth of 1 GHz. In this paper, the
completed 250 deg^2 data from l=+25.8deg to +49.7deg are presented with a grid
spacing of 30" and a typical rms noise level of ~0.5 K for 12CO at the channel
width of 0.16 km/s and ~0.3 K for 13CO and C18O at 0.17 km/s. The high quality
data with moderate resolution (50"), uniform sensitivity, and high spatial
dynamic range, allow us to investigate the details of molecular clouds (MCs)
traced by the three CO isotope lines. Three interesting examples are briefly
investigated, including distant Galactic spiral arms traced by CO emission with
VLSR<0 km/s, the bubble-like dense gas structure near the HII region W40, and
the MCs distribution perpendicular to the Galactic plane.
