ESA's infrared space observatory (ISO): The development programme

ESA's Infrared Space Observatory, ISO, was put into orbit by Ariane on 17 November 1995 and it has since entered the routine operations phase, providing excellent results for the scientific community. ISO provides an unprecedented opportunity to make scientific observations of very weak infrared radiation sources. To make such measurements, the telescope and scientific instruments are kept at near absolute zero temperature by enclosing them in a helium-cooled cryostat, effectively a large thermos-flask with superfluid helium at 1.7 K. The development of the observatory proved to be a very challenging task as there was little experience available with the advanced technologies required for the mission, e.g. cryogenics, optics and attitude control. This paper describes the mission, the satellite, the development programme and the organisation of the project. Both the development problems encountered and the technology achievements of the programme are emphasized. The performance of the satellite in orbit is also reported. ISO is an excellent observatory for the scientific community. It is a unique facility and will be the only one in the world with such capabilities for at least the next decade. (C) 1997 International Astronautical Federation. Published by Elsevier Science Ltd.