SNAP is a proposed space mission designed to further investigate high-z SNe.  With a 2-meter mirror, and a full square degree field of view, it is predicted to find nearly 2,000 SNe per year over its 3 year lifetime.  It would also find about 50 million galactic redshifts out to z=3.5, identify 15,000 galaxy clusters, and detect quasars and GRB afterglows out to z~10.

The cosmological goals of SNAP include measuring WM to within 0.02, as well as WL and q0 to within 0.04.  Besides that, the data generated would be able to find the equation of state for the dark energy to within 5%, as well as search for evidence for w varying as a function of z.

From SNAP Homepage