Infrared telescopes for a space observatory

A cryogenically cooled infrared telescope of 1 to 2 meter aperture is discussed. Advantages of the space environment are detailed, and design considerations for cooled telescopes are given, leading to a schematic and preliminary design of a telescope for the space shuttle. The advantages of the sortie mode to an infrared observatory are dealt with and possible use of an ambient temperature telescope is discussed. Costs of infrared telescope observation are indicated.