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G. Illingworth (UCO/Lick, University of California)
The Hubble Deep Fields, and the followup spectroscopic and IR observations, demonstrated how crucial deep, high resolution multi-band, UV-optical images are for quantifying galaxy formation and evolution over redshifts from z~5 to the present day. However, these pathfinder observations also showed the limitations of working over a very small field, both through the impact of cosmic variance and through the low statistical weight from small sample sizes. HST, using the new Advanced Camera, the ACS, will increase the area covered in deep, photometrically-robust, multiband surveys very substantially, though the investment of time will be very large. With the imminent operation of ~15 ground-based multi-object spectroscopic telescopes in the 6--10 m size range, the advent of ALMA, and the areal coverage of missions such as Chandra and XMM and SIRTF, HST plus ACS will be a limiting factor for the next generation of wide-area, distant galaxy surveys. High spatial resolution, multiband data will be essential for quantitative characterization of large samples of galaxies across all the physical permutations demonstrated by these richly varied objects. SNAP, with its very wide field, wide optical-near IR spectral coverage, excellent photometric performance, and large numbers of filters would be an immensely powerful survey instrument to complement and build on the capabilities of HST and the earlier generations of surveys.