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Optical design of NICMOS: the second-generation infrared instrument for the Hubble Space Telescope

NICMOS is the near infrared second generation instrument for the Hubble Space Telescope. The NICMOS instrument consist of three infrared cameras with spectral response between 1 and 2.5 micrometers whose fields of view are 11, 19.3 and 51.1 arc seconds. Each camera has an independent filter wheel with 20 positions. In the wide field camera, two grisms will be substituted for two of the filters. Some unique challenges arise because (1) NICMOS must interface with HST, (2) it is a low background infrared device with warm optics and (3) it has a large cryogenic dewar enveloping the detectors. This paper summarizes the optical configuration of the instrument as well as some of the requirements that drive the design. Expected performance will be presented.