Wide-field infrared survey explorer science payload update

The Wide Field Infrared Survey Explorer is a NASA Medium Class Explorer mission to perform an all-sky survey in four infrared wavelength bands. The science payload is a cryogenically cooled infrared telescope with four 1024² infrared focal plane arrays covering from 2.8 to 26 &#956;m. Advances in focal plane technology and a large aperture cryogenic telescope allow an all-sky survey to be performed with high sensitivity and resolution. An efficient survey is obtained using a cryogenic scan mirror to freeze the field of view on the sky over the 9.9-second frame integration time. Mercury cadmium telluride (MCT) detectors, cooled to 32 K, are used for the two midwave channels (3.3 &#956;m and 4.6 &#956;m), and Si:As detectors, cooled to < 8.3 K, are used for the two long wavelength channels (12 &#956;m and 23 &#956;m). Cooling is provided by a two-stage solid hydrogen cryostat which provides temperatures < 17 K and < 8.3 K at the telescope and Si:As focal planes, respectively. The science payload supports operations on orbit for the seven-month baseline mission with a goal to support a 13-month extended mission, if possible. The payload recently passed CDR and is being fabricated. This paper provides a payload overview and discusses instrument requirements and performance.