Calibrating the Galaxy Cluster Mass-Observable Relations at z=0.9

We propose deep XMM observations (totalling 234ks) of three z>0.75 galaxyclusters to measure temperature profiles and hence precise hydrostatic masses,completing a sample of six. This sample will constrain the normalisation of theYxM scaling relation to 10% at z0.9, and its evolution parameter to 12%. TheSunyaevZel dovich effect mass estimators will also be calibrated with a similarprecision (a first at these redshifts). We will also measure precise gasfractions (leading to improved cosmological constraints), and study theevolution of the metal abundance of the intracluster medium. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]