Infrared Space Observatory

The Infrared Space Observatory ( ISO) was operated as an observatory space telescope for infrared range from 2.4 to 240 microns. As space observatory above the Earth's atmosphere ISO could observe celestial objects even at wavelengths that are from out of the ground can not be used by the absorption of the atmosphere. ISO was moving in a highly eccentric orbit with an orbital period of 24 hours.


ISO was developed by the European Space Agency ESA with smaller amounts from NASA and the Japanese Space Research Institute ISAS. The four instruments were contributed by consortia from different European countries. The ISO telescope had a primary mirror diameter of 60 cm and was cooled to suppress its own thermal radiation by liquid helium.

ISO had four observation instruments:

  • The infrared camera ISOCAM, the wavelength range covering 2.5-17 microns with two detectors each of 32 by 32 pixels;
  • The ISOPHOT photopolarimeter for the wavelength range from 2.5 to 240 microns;
  • The short- wave spectrometer SWS for the wavelength range from 2.4 to 45 microns;
  • The long wavelength spectrometer LWS for the wavelength range 45-197 microns.

Mission History

ISO was launched on 17 November 1995 at 1:20 UTC clock with Arianespace Flight V 80 aboard an Ariane 44P from the Kourou space center in an orbit 500-71850 km altitude with 5.25 ° equatorial inclination. ISO then changed before the start of the observations its orbit into an orbit between 1038-70578 km altitude with 5.2 ° inclination equator and 24 hour turnaround time. The nominal operation of the satellite lasted until the exhaustion of the coolant on 8 April 1998. Afterwards could be weiterbeobachtet with some of the detectors have until 10 May 1998 only passive cooling. ISO conducted a total of about 26,000 observations on behalf of more than 500 teams of astronomers. ISO was turned off just before May 16, 1998, the web height has been reduced in order to speed up the re-entry.


ISO was on the results of the IRAS mission, especially its sky survey build. Despite having the same size telescope like IRAS ISO was much more efficient for the study of individual objects through the advanced instruments and the distinct spectroscopic capabilities. Among the most important discoveries of the ISO contribute to infrared astronomy could include:

  • Discovery of water in a variety of objects, from planets in our solar system to distant galaxies
  • Molecules Eisverbindungen and chemical processes in the interstellar medium and the environment of stars
  • Determination of the energy sources of infrared galaxies
  • Discovery of infrared galaxies at a redshift of 1, which were significantly more likely to this earlier stage of development of the universe than today