We present the results of a study of the performance of InGaAs detectors conducted for the SuperNova Acceleration Probe (SNAP) dark energy mission concept. Low temperature data from a nominal 1.7um cut-off wavelength 1kx1k InGaAs photodiode array, hybridized to a Rockwell H1RG multiplexer suggest that InGaAs detector performance is comparable to those of existing 1.7um cut-off HgCdTe arrays. Advances in 1.7um HgCdTe dark current and noise initiated by the SNAP detector research and development program makes it the baseline detector technology for SNAP. However, the results presented herein suggest that existing InGaAs technology is a suitable alternative for other future astronomy applications.

Large format (1k x 1k and 2k x 2k) near infrared detectors manufactured by Rockwell Scientific Center and Raytheon Vision Systems are characterized as part of the near infrared R&D effort for SNAP (the Super-Nova/Acceleration Probe). These are hybridized HgCdTe focal plane arrays with a sharp high wavelength cut-off at 1.7 um. This cut-off provides a sufficiently deep reach in redshift while it allows at the same time low dark current operation of the passively cooled detectors at 140 K. Here the baseline SNAP near infrared system is briefly described and the science driven requirements for the near infrared detectors are summarized. A few results obtained during the testing of engineering grade near infrared devices procured for the SNAP project are highlighted. In particular some recent measurements that target correlated noise between adjacent detector pixels due to capacitive coupling and the response uniformity within individual detector pixels are discussed.

P-channel, backside illuminated silicon CCDs were developed and fabricated on high-resistivity n-type silicon. Devices have been exposed up to 1x1011 protons/cm2 at 12 MeV. The charge transfer efficiency and dark curent were measured as a function of radiation dose. These CCDs were found to be significantly more radiation tolerant than conventional n-channel devices. This could prove to be a major benefit for long duration space missions.

Precision near infrared (NIR) measurements are essential for the next generation of ground and space based instruments. The SuperNova Acceleration Probe (SNAP) will measure thousands of type Ia supernovae up to a redshift of 1.7. The highest redshift supernovae provide the most leverage for determining cosmological parameters, in particular the dark energy equation of state and its possible time evolution. Accurate NIR observations are needed to utilize the full potential of the highest redshift supernovae. Technological improvements in NIR detector fabrication have lead to high quantum efficiency, low noise detectors using a HgCdTe diode with a band-gap that is tuned to cutoff at 1:7 1m. The effects of detector quantum efficiency, read noise, and dark current on lightcurve signal to noise, lightcurve parameter errors, and distance modulus ?ts are simulated in the SNAP sim framework. Results show that improving quantum efficiency leads to the largest gains in photometric accuracy for type Ia supernovae. High quantum efficiency in the NIR reduces statistical errors and helps control systematic uncertainties at the levels necessary to achieve the primary SNAP science goals.

The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.