The ROSAT mission

The ROSAT mission
  • Künstlerische Darstellung des Rosat%2dSatelliten im All Künstlerische Darstellung des Rosat%2dSatelliten im All

    Artist's impression of the ROSAT satellite in space

    Artist's impression of the ROSAT satellite as it orbits the Earth. ROSAT was used to conduct research into X-ray sources.

  • Rosat beim Test in der Weltraum%2dSimulationskammer Rosat beim Test in der Weltraum%2dSimulationskammer

    ROSAT undergoing tests in the space simulation chamber

    The ROSAT satellite undergoing tests in the space simulation chamber at Dornier.

  • Rosat startete am 1. Juni 1990 an Bord einer Delta%2dII%2dRakete von Cape Canaveral Rosat startete am 1. Juni 1990 an Bord einer Delta%2dII%2dRakete von Cape Canaveral

    ROSAT was launched from Cape Canaveral on 1 June 1990 on board a Delta II rocket

    This X-ray satellite was launched from Cape Canaveral in Florida on 1 June 1990 on board a Delta II rocket property of NASA. Originally, the plan was to put Rosat in Earth orbit on board a US Space Shuttle. Following the explosion of Challenger in 1986 (when ROSAT was under construction), it was decided to launch the X-ray satellite into orbit on board a rocket.


The launch of the ROentgen SATellite (ROSAT) into space on 1 June 1990 marked the start of a mission that would allow researchers to perform an all-sky survey of X-ray sources with an imaging telescope for the first time. X-rays arise in the Universe by unusually hot, high-energy processes, which often entail extreme states of matter such as black holes or neutron stars.

Determining the energy distribution of X-ray radiation is important to understand these processes. Furthermore, the position of the X-ray source in the sky needs to be deduced as accurately as possible to investigate extended structures, as well as to obtain supplementary information about the X-ray source in other wavelengths. These observations cannot be performed from the ground because our atmosphere absorbs X-ray radiation. To investigate radiation sources in space, a telescope had to be placed in Earth orbit.

The ROSAT project is a collaborative venture between Germany the United States and the United Kingdom, and was developed, built and launched on behalf of and under the leadership of the German Aerospace Center (DLR). The German Space Operations Center (GSOC) later took control of the satellite in close coordination with the collaborating research institutes.

ROSAT, the largest X-ray observatory of its time, was intended to fulfil two objectives during its planned 18-month mission; during the first six months, researchers at the Max-Planck Institute for Extraterrestrial Physics (MPE) in Garching near Munich performed an all-sky survey and compiled a space atlas in the X-ray regime. Then, ROSAT was to carry out detailed observations of selected X-ray sources over the course of one year. 

Since the satellite was, not only operational after the end of its official mission period, but still detecting X-ray sources, the mission was extended several times. The satellite detected about 80,000 cosmic X-ray sources and an additional wide-field camera on board added another 6000 sources in the extreme ultraviolet regime. During its eight years of operation, more than 4000 scientists from 24 countries took advantage of the opportunity to commission and analyse measurements. In each case, the data was released into a public domain archive one year after each observation.

As early as January 1991, one of the two Position Sensitive Proportional Counter (PSPC) detectors and one filter of the British wide-field camera were destroyed by overheating. In 1994, the fuel supply ran out on the second PSPC, and observations with this detector had to be terminated. However, observations of X-ray sources continued with the US High Resolution Imager (HRI).

The failure of the primary star tracker in 1998 caused the HRI to point directly at the Sun, causing irreversible damage. Following that incident, on 12 February 1999, more than eight and a half years after its launch, the X-ray satellite telescope ROSAT was abandoned and shut down.

Mission parameters

Launch date1 June 1990
Launch siteCape Canaveral, Florida, USA
Launch vehicleDelta II rocket
End of mission12 February 1999
Control CentreGerman Space Operations Center (GSOC), Oberpfaffenhofen
Ground stationDLR's ground station in Weilheim
Launch mass2,426 kilograms
External dimensions2.20 metres x 4.70 metres x 8.90 metres
Orbit around EarthOriginally at an altitude of approximately 580 kilometres with an inclination of 53°


a) X-ray telescope:
Four Wolter mirrors: largest diameter 83 centimetres, focal length of 2.4 metres, angular resolution better than five seconds of arc
Sensitivity range of telescope: approx. 0.1 to 2.4 keV
Detectors: Two Position Sensitive Proportional Counters (PSPC); one microchannel plate detector (High Resolution Imager, HRI)
b) Wide-field camera (WFC) for observations in the extreme ultraviolet range

Last modified:
30/09/2011 10:24:35



Sabine Göge
German Aerospace Center (DLR)

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German Aerospace Center (DLR)

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