Wide field x-ray surveys: wide field x-ray telescope (WFXT) and notional wide field imager (N-WFI)

Wide field X-ray surveys require large field of view telescopes operating in a step and repeat or slow scanning mode in order to cover large areas of the sky efficiently. Here we discuss two similar, yet different designs for a wide field survey mission that can each be accomplished for a cost of less than ~$1B (FY 2012) and that cover many hundreds to several thousand deg², with medium depth ~few × 10⁻¹⁶ erg s⁻¹cm², and several 10’s of degrees with very long exposure time to a depth approaching ~3 × 10⁻¹⁷ erg s⁻¹cm². We review the WFXT design and compare it with the Notional Wide Field Imager (N-WFI) concept that was developed by the NASA CST in response to a charge from NASA to define generic (or notional) missions that can accomplish some (or all) of the IXO science, but at a reduced cost.