Infrared Space Observatory

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Infrared Space Observatory
Type: Space telescope
Operator: European space agencyESA ESA
COSPAR-ID : 1995-062A
Mission dates
Dimensions: 2498 kg
Begin: November 17, 1995, 1:20 UTC
Starting place: CSG , ELA-2
Launcher: Ariane 44P V-80
Status: out of service since May 16, 1998
Orbit data
Rotation time : approx. 24 h
Orbit inclination : 5.2 °
Apogee height 70578 km
Perigee height 1038 km

The Infrared Space Observatory ( ISO ) was a space telescope for the infrared range from 2.4–240 µm. As a space observatory above the earth's atmosphere , ISO was able to investigate celestial objects between 1995 and 1998 even at wavelengths that cannot be observed from the earth due to the absorption of the atmosphere. ISO moved in a highly eccentric earth orbit with an orbital time of 24 hours.


ISO was developed by the European space agency ESA with minor contributions from NASA and the Japanese space research institute ISAS (part of JAXA since 2003 ). The ISO telescope had a main mirror of 60 cm in diameter and was cooled with liquid helium to suppress its own heat radiation .

The four observation instruments were contributed by consortia from different European countries:

  • the infrared camera ISOCAM, which covered the wavelength range 2.5–17 µm with two detectors of 32 by 32 pixels each
  • the photo polarimeter ISOPHOT for the wavelength range 2.5–240 µm
  • the shortwave spectrometer SWS for the wavelength range 2.4–45 µm
  • the long wave spectrometer LWS for the wavelength range 45–197 µm.

Mission history

ISO was launched on November 17, 1995 at 1:20 UTC with Arianespace Flight V 80 on board an Ariane 44P from the Center Spatial Guyanais into an orbit between 500 and 71,850 km altitude with an inclination of 5.25 ° at the  equator . Before starting the observations, ISO then changed its orbit to an orbit between 1,038 and 70,578 km altitude with 5.2 ° equatorial inclination and a 24-hour orbit.

The nominal operation of the satellite lasted until the coolant was exhausted on April 8, 1998. After that, observations could be continued until May 10, 1998 with only passive cooling with some of the detectors. ISO carried out a total of over 26,000 observations on behalf of over 500 teams of astronomers. Just before ISO was shut down on May 16, 1998, which was swathheight reduced to the re-entry to speed.


ISO was able to build on the results of the IRAS mission, in particular its sky survey . Despite the same telescope size as IRAS, ISO was much more efficient for examining individual objects thanks to the further developed instruments and pronounced spectroscopic capabilities. Key discoveries that ISO contributed to infrared astronomy include:

Technical specifications

Takeoff mass 2498 kg
Cryostat 2250 l superfluid helium -4, temp. 1.8 K .
height 5.3 m
Diameter or width 2.3 m
Mirror diameter 60 cm
Duration of use approx. 2 years and 7 months
train Earth orbit 1038 - 70,578 km high
Launcher Ariane 44P
Start date November 19, 1995
Mission end May 16, 1998

Web links

Individual evidence

  1. Infrared Space Observatory (ISO) ( Memento from October 16, 2006 in the Internet Archive )
  2. ISO overview. ESA, October 14, 2003, accessed October 10, 2012 .
  3. Data from: Infrared Space Observatory (ISO) ( Memento from October 16, 2006 in the Internet Archive )