Artist's impression of the Infrared Space Observatory (ISO) in orbit over the Earth. Due for launch in September 1995, ISO will have a 60cm diameter Cassegrain telescope & a variety of infrared detectors, including a camera, an imaging photopolarimeter & 2 spectrometers. ISO will study ordinary & active galaxies, quasars, the birth of stars, & the infrared continuum. Developed by the European Space Agency (ESA), ISO will be 5.3m tall & 2.8m wide, It will weigh 2400 kg at lift-off. Superfluid helium will keep the telescope and instruments at temperatures of 2K-4K during ISO's expected lifetime of 18 months.