The SNAP space mission

The SNAP space mission concept is designed to explore dark energy with Type Ia supernova distance-luminosity measurements and with weak lensing angular distance correlation power spectrum. The supernova program uses photometric discovery and detailed follow-up observations of at least 2000 Type Ia supernovae with redshifts ranging from 0.3 to 1.7. The weak lensing program uses a deep small field survey and a shallower large field survey with photometry, position and shape measurement of several million galaxies. The instrument sits at the focus of a ∼2-m diameter three-mirror anastigmat telescope with a 1.4 deg2 field of view. It consists of an imager that instruments 0.7 deg2 of the field of view, and a low-resolution spectrograph. Both the photometer and spectrograph use visible and near-infrared detectors to span the wavelength range 400-1700 nm. Wavelength is covered with two detector materials implemented with different readout architectures-CCDs for the visible and HgCdTe hybrid pixel detectors for the near-infrared. While these detector technologies are familiar in HEP experiments, they used in a very different manner, namely photon counting. The physics, architecture and characteristics of these detectors and how they are used will be presented.