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.
1960s
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
The Vela 5B spacecraft in low Earth oribt. (Credit: USAF)
- 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
1970s
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
An artist's conception of the Copernicus (OAO-3) satellite in orbit. (Credit: NASA)
- 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
1980s
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
An artist's impression of the Exosat spacecraft. (Credit: ESA)
- 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
1990s
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
An artist's conception of ROSAT. (Credit: MPE)
- 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
2000s
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
An artist's impression of the XMM-Newton satellite in orbit. (Credit: ESA/D. Ducros)
- 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
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
Artist's conception of NuSTAR in orbit. The background is an image of the Galactic Center from Chandra. (Credit: NASA)