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   PR # 22189
    ASCA provides the first opportunity to take full advantage of the    
    potential of x-ray observations to measure accurately the gravitating
    mass of rich clusters of galaxies with high gas temperatures ($kT\gax
    3$~keV).  ASCA has adequate imaging and spectroscopic capabilities to
    determine {\em both} parameters required to determine the gravitating
    mass -- the gas density and gas temperature profiles.  We propose to 
    observe rich cluster A2670, for which extensive optical information  
    is available in the literature. From this observation we will be able
    to determine the total gravitating mass, the mass-to-light ratio, and
    baryon fraction within $1.5~h_{50}^{-1}$~Mpc from the cluster center.
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