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X-ray Astronomy Satellites & Missions

X-ray Astronomy Satellites & Missions

We present here some of the many satellites which have detected electromagnetic radiation between 0.01 and 50 keV from non-solar sources. They are arranged by the decade in which the satellite was launched. Over the decades, the sensitivity of the X-ray detectors has increased greatly. In addition, our ability to focus X-rays has developed, allowing us to now obtain high-quality X-ray images of many fascinating celestial objects.

To see all of the X-ray satellites and missions, see this timeline of high-energy astrophysics missions.

The Vela 5B spacecraft in low Earth oribt.

The Vela 5B spacecraft in low Earth oribt. (Credit: USAF)


The first satellite which detected cosmic X-rays (not to be confused with the first detection of cosmic X-rays!) was called the Third Orbiting Solar Observatory, or OSO-3. Even its name tells you that it was intended primarily to observe the Sun, which it did very well during its 2 year lifetime, but it also detected a flaring episode from the source Sco X-1 and it measured the diffuse cosmic X-ray background. In fact, none of the satellites launched in the 1960s were dedicated to cosmic X-ray astronomy... so all of the discoveries they made were just little gifts from the missions as they did their "real" jobs. For example, the Vela satellites were launched to watch for whether or not countries on Earth exploded any nuclear bombs in the atmosphere!

All X-ray missions active during the 1960s

Vela 5A/B and 6A/B May 1969 - June 1979
Cosmos Series March 1962 - Present
OSO Series March 1962 - October 1978
ESRO-2B May 1968 - December 1968
OGO September 1964 - March 1972

Artist's conception of the Copernicus satellite

An artist's conception of the Copernicus (OAO-3) satellite in orbit. (Credit: NASA)


The decade of the 1970s was a very busy one for X-ray astronomy. The first orbiting mission which was dedicated to celestial X-ray astronomy was Uhuru, launched in 1970. Uhuru had a simple complement of instrumentation covering the energy range 2-20 keV. It provided the first comprehensive view of the entire X-ray sky. The final catalog of point sources Uhuru detected contained 339 objects, which were primarily binary stellar systems, supernova remnants, Seyfert galaxies and clusters of galaxies.

Many important missions followed Uhuru in the 1970s, including ANS, Copernicus, SAS-3, Ariel V, and OSO 8. These missions discovered X-ray bursts, numerous pulsars, and obtained the first detailed X-ray spectra. Another great leap forward occurred in 1977 with the launch of NASA's first High Energy Astrophysical Observatory ( HEAO-1). HEAO-1 carried 4 major instruments, covering the energy band 0.2 keV to 10 MeV. It generated a catalog of approximately 850 point sources during its 18 month lifetime, allowed the first comprehensive measurement of the diffuse X-ray background, and performed time variability studies on millisecond time scales. This mission was followed by HEAO-2 (also known as the Einstein Observatory), which was the first mission to use grazing incidence focusing optics for celestial astronomy (which increased the detection sensitivity by a factor of nearly 1000!).

All X-ray missions active during the 1970s

Ariel Program April 1962 - February 1982
Hakucho February 1979 - April 1985
HEAO August 1977 - May 1981
Venera Program February 1961 - July 1984
ISEE-3 August 1978 - May 1997
OSO March 1962 - October 1978
SAS December 1970 - April 1979
Aryabhata April 1975
Salyut-4 December 1974 - February 1977
ANS August 1974 - June 1977
Skylab July 1973
Copernicus August 1972 - February 1981
TD-1A March 1972 - May 1974
Cosmos Series March 1962 - Present
Vela 5A/B and 6A/B May 1969 - June 1979

An artist's conception of the Exosat image

An artist's impression of the Exosat spacecraft. (Credit: ESA)


During the 1980s, as NASA struggled to recover from the Space Shuttle Challenger accident, the European, Japanese, and Russian Space Agencies continued to launch successful X-ray astronomy missions. In particular, this decade saw the launches of the European X-ray Observatory Satellite (EXOSAT), Granat, the Kvant module, Tenma, and Ginga. These missions were more modest in scale than the HEAO program in the 1970s, and were directed toward in-depth studies of known phenomena.

All X-ray missions active during the 1980s

Granat December 1989 - November 1998
Phobos July 1988 - March 1989
Kvant-1 April 1987 - March 2001
Ginga February 1987 - November 1991
Spacelab November 1983 - April 1998
Spartan-1 June 1985
EXOSAT May 1983 - April 1986
Astron March 1983 - June 1989
Tenma February 1983 - November 1985
Venera Program February 1961 - July 1984

An artist's conception of ROSAT

An artist's conception of ROSAT. (Credit: MPE)


In the 1990s the ROSAT survey detected more than 100,000 X-ray objects, the ASCA mission made the first sensitive measurements of the X-ray spectra from these objects, and RXTE studied their timing properties. These have been supplemented by a host of other missions, with other primary goals, but which contain instruments sensitive to high-energy cosmic radiation (such as Ulysses and Wind). Both individually and collectively, these satellites have provided an unprecedented view of the X-ray Universe. Satellites launched late in the decade, Chandra and XMM, had an order of magnitude improvement in sensitivity for imaging, and promise new and exciting breakthroughs in the journey of X-ray astronomy exploration.

All X-ray missions active during the 1990s

XMM December 1999 - Present
Chandra July 1999 - Present
Beppo SAX April 1996 - April 2002
RXTE December 1995 - January 2012
Wind November 1994 - Present
ALEXIS April 1993 - April 2005
ASCA February 1993 - March 2001
DXS January 1993
EURECA July 1992 - July 1993
BBXRT December 1990
Ulysses October 1990 - June 2009
ROSAT June 1990 - February 1999

An artist's impression of the XMM-Newton satellite in orbit

An artist's impression of the XMM-Newton satellite in orbit. (Credit: ESA/D. Ducros)


As the 21st century began, XMM-Newton, the Chandra X-ray Observatory, and RXTE were the work-horses of X-ray astronomy. In early 2000 X-ray astronomy suffered from the loss of Astro-E, which was to provide high resolution spectroscopy through innovative X-ray micro-calorimeters. Its replacement, Suzaku, also experienced a loss of the high resolution spectroscopy instrument, speaking to the difficult realities scienctists and engineers face when constructing and operating space-based satellites. In addition, Swift launched with an X-ray telescope.

All X-ray missions active during the 2000s

RXTE December 1995 - January 2012
Chandra July 1999 - present
XMM December 1999 - present
Swift November 2004 - present
Suzaku (ASTRO-E2) July 2005 - Present
MAXI July 2009 - present

An artist's impression NuSTAR

Artist's conception of NuSTAR in orbit. The background is an image of the Galactic Center from Chandra. (Credit: NASA)

2010s and Beyond

As we entered the 2010s, some of the X-ray astronomy work-horses, XMM-Newton and the Chandra X-ray Observatory, were still going strong. RXTE was winding down it's run, and was decommissioned in 2012. Even though Swift's primary mission was to study gamma-ray bursts, it was also providing spectacular views of the X-ray universe. NuSTAR launched in 2012, bringing focusing optics to high-energy X-rays for the first time. The next chance for X-ray micro-calorimeters comes with the launch of Astro-H in the mid-2010s.

All X-ray missions active during the 2010s

RXTE December 1995 - January 2012
Chandra July 1999 - present
XMM December 1999 - present
Swift November 2004 - present
Suzaku (ASTRO-E2) July 2005 - Present
MAXI July 2009 - present
NuSTAR June 2012 - present

A service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC

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