Effect of the Shuttle contaminant environment on a sensitive infrared telescope

A sensitive ir telescope on the Space Shuttle Orbiter will be limited in its performance by fluctuations in the ir radiation from the natural environment and the contaminant atmosphere. Models of the Orbiter's contaminant atmosphere were used to predict its spectral radiance from 3 microm to 300 microm. At 350 km, statistical fluctuations in the radiation from a water vapor column density of 10(12) cm(-2) produce a noise equivalent power of about 2 x 10(-17) W/Hz(1/2) in a 1 min of arc field of view of a 1-m diameter telescope with a 10-microm spectral bandwidth. This noise is somewhat smaller than the expected contribution from zodiacal light from 5 microm to 30 microm. The column density of all ir emitting molecules can be kept as low as 10(12) cm(-2) only if restrictions on rocket firings and liquid vents are maintained. The relatively low frequency of particle sightings from Skylab, coupled with improvements in Orbiter venting techniques, indicates that sightings of particles 2 microm and larger in radius will not seriously hamper tele cope performance provided that liquid vents and rocket firings are properly restricted.