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   51265
   We propose a re-observation of the Lockman Hole, where the deepest
   ROSAT observations (PSPC: 200 ks, HRI: 1 Ms in progress) exist. We are
   planning to cover the ROSAT surveyed area (r < 18.5 arcmin) with 4
   pointings of each 80 ks. It is a great merit to study the origin of the
   CXB above 2 keV that the soft X-ray catalogue with optical
   identification is available. It will also enable us to generate a
   perfect wide-band CXB spectrum in the range of 0.1-10 keV.
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