Exploring dark energy with SNAP

The accelerating expansion of the Universe is one of the most surprising and potentially profound discoveries of modern cosmology. Measuring the acceleration well enough to meaningfully constrain interesting physical models requires improvements an order of magnitude beyond on-going and near-term experiments. The Supernova/Acceleration Probe has been conceived as a powerful yet simple experiment to use Type la supernovae and weak gravitational lensing to reach this level of accuracy. As fundamentally different causes for the acceleration map into very small differences in observational parameters for all relevant cosmological methods, control of systematics is especially important and so has been built into the SNAP mission design from the very beginning. Though focused on the study of the accelerating Universe, the overall SNAP instrument suite is quite general and able to make unique contributions to a wide variety of astronomical studies. The baseline satellite consists of a 2-m anastigmat telescope, with a 0.7 square degree focal plane paved with optical and NIR imaging arrays. Spectroscopy can be obtained using a high-throughput low-resolution optical + NIR integral field spectrograph. The baseline science programs will result in a 15 square degree "deep field" having temporal coverage every 4 days and summing to m(AB) similar to 30.3 in all colors - to be used for discovery and follow-up of some 2000 Type Ia supernova in the range 0.1 < z < 1.7 - and a wide area survey spanning 1000 square degrees and reaching m(AB) similar to 27.7 in all colors - to be used to measure the weak lensing power spectrum well into the non-linear regime. A panoramic survey covering 10,000 square degrees to m(AB) similar to 26.7 in all colors is also possible. This baseline dataset represents a gold mine for archival astronomical research and follow-up with JWST, while guest observer survey programs will substantially broaden the impact that SNAP will have. (c) 2005 Elsevier B.V. All rights reserved.