AN UNBIASED VALUE OF OMEGA FROM CLUSTER INFALL AND GRAVITATIONAL LENSING

We combine various methods to derive an unbiased value of the cosmolog ical density parameter Omega. We consider the analysis of redshift-spa ce envelopes of infall patterns around rich clusters of galaxies and e stimates of the cluster mass at large radii from gravitational lensing . We estimate the uncertainty in the value of Omega taking into accoun t the imperfect separation of the background, the elongation of the cl uster and the resolution of imaging gravitational lensing. Future obse rvations using the Hubble Space Telescope will constrain Omega using t his method.