Program: GN-2007A-Q-75

Gravitational lenses have proven to be powerful tools for placing constraints on cosmological parameters and for studying the astrophysics of moderate-redshift galaxies. However, in order to be so exploited, the redshifts of both the lensing galaxy and the background source need to be measured. In this proposal, we request time to measure redshifts for four out of the five CLASS gravitational lens systems with incomplete redshift information. Obtaining these redshifts will significantly increase the utility of the CLASS lens sample for statistical studies.