Decelerating and Dustfree: Efficient Dark Energy Studies with
Supernovae and Clusters


We propose novel techniques for achieving both high redshift 
observations and robust systematics control simultaneously in
supernovae and cluster measurements, eliminating difficulties in the
use of GOODS data, and greatly increasing HST efficiency and science 
yield per orbit.  These key measurements will serve as the linchpin 
for next generation studies of dark energy and cosmology. As 
demonstrated in Cycle 14, by targeting massive galaxy clusters at 
z > 1 we obtain a high efficiency in detection of Type Ia supernovae, 
minimization of the dominant systematic of host galaxy extinction 
using cluster ellipticals, and we leverage cluster studies through 
weak lensing, optical, X-ray, and Sunyaev-Zel'dovich measurements.
The data will set the stage for improvement of (unbiased) supernova 
constraints on dark energy time variation by a factor two, and serve 
as a bedrock scientific resource for cluster studies.