|Names||High Throughput X-ray Spectroscopy Mission
X-ray Multi-Mirror Mission
|Mission type||X-ray astronomy|
|Operator||European Space Agency|
|Mission duration||Planned: 2 years
Elapsed: 16 years, 1 month and 27 days
|Manufacturer||Dornier Satellitensysteme, Carl Zeiss AG, Media Lario, MMS Bristol, BPD Difesa e Spazio, Fokker Space BV|
|Launch mass||3,764 kg (8,298 lb)|
|Dry mass||3,234 kg (7,130 lb)|
|Dimensions||Length: 10.8 m (35 ft)
Span: 16.16 m (53 ft)
|Start of mission|
|Launch date||10 December 1999, 14:32UTC|
|Rocket||Ariane 5G No. 504|
|Launch site||Guiana Space Centre ELA-3|
|Entered service||1 July 2000|
|Semi-major axis||65,648.3 km (40,792.0 mi)|
|Perigee||5,662.7 km (3,518.6 mi)|
|Apogee||112,877.6 km (70,138.9 mi)|
|Epoch||4 February 2016, 01:06:30 UTC|
|Type||3 × Wolter type-1|
|Diameter||Outer mirror: 70 cm (28 in)
Inner mirror: 30.6 cm (12 in)
|Focal length||7.5 m (25 ft)|
|Collecting area||4,425 cm2 (686 sq in) at 1.5 KeV
1,740 cm2 (270 sq in) at 8 KeV
|Wavelengths||1 to 120 Ångstroms|
|Resolution||5 to 14 arcseconds|
XMM-Newton, also known as the X-ray Multi-Mirror Mission and the High Throughput X-ray Spectroscopy Mission, is an X-ray space observatory launched by the European Space Agency in December 1999 on an Ariane 5 rocket. It is the second cornerstone mission of ESA's Horizon 2000 programme. Named for physicist and astronomer Sir Isaac Newton, the spacecraft is tasked with investigating interstellar X-ray sources, performing narrow- and broad-range spectroscopy, and performing the first simultaneous imaging of objects in both X-ray and optical (visible and ultraviolet) wavelengths. Originally scheduled for a two-year mission, the spacecraft remains in good health and has received mission extensions through 2016. As of February 2016, more than 4,300 papers have been published about either XMM-Newton or the scientific results it has returned.
Concept and mission history
The observational scope of XMM-Newton includes the detection of X-ray emissions from astronomical objects, detailed studies of star-forming regions, investigation of the formation and evolution of galaxy clusters, the environment of supermassive black holes and mapping of the mysterious dark matter.
In 1982, even before the launch of XMM-Newton's predecessor EXOSAT in 1983, a proposal was generated for a "multi-mirror" X-ray telescope mission. The XMM mission was formally proposed to the ESA Science Programme Committee in 1984 and gained approval from the Agency's Council of Ministers in January 1985. That same year, several working groups were established to determine the feasibility of such a mission, and mission objectives were presented at a workshop in Denmark in June 1985. At this workshop, it was proposed that the spacecraft contain 12 low-energy and 7 high-energy X-ray telescopes. The spacecraft's overall configuration was developed by February 1987, and drew heavily from lessons learned during the EXOSAT mission; the Telescope Working Group had reduced the number of X-ray telescopes to seven standardised units. In June 1988 the European Space Agency approved the mission and issued a call for investigation proposals (an "announcement of opportunity"). Improvements in technology further reduced the number of X-ray telescopes needed to just three.
In June 1989, the mission's instruments had been selected and work began on spacecraft hardware. A project team was formed in January 1993 and based at the European Space Research and Technology Centre (ESTEC) in Noordwijk, Netherlands. Prime contractor Domier Satellitensysteme (a subsidiary of the former DaimlerChrysler Aerospace) was chosen in October 1994 after the mission was approved into the implementation phase, with development and construction beginning in March 1996 and March 1997, respectively. The XMM Survey Science Centre was established at the University of Leicester in 1995. The three flight mirror modules for the X-ray telescopes were delivered by Italian subcontractor Media Lario in December 1998, and spacecraft integration and testing was completed in September 1999.
XMM left the ESTEC integration facility on 9 September 1999, taken by road to Katwijk then by the barge Emeli to Rotterdam. On 12 September, the spacecraft left Rotterdam for French Guiana aboard Arianespace's transport ship MN Toucan. The Toucan docked at the French Guianese town of Kourou on 23 September, and was transported to Guiana Space Centre's Ariane 5 Final Assembly Building for final launch preparation.
Launch of XMM took place on 10 December 1999 at 14:32 UTC from the Guiana Space Centre. XMM was lofted into space aboard an Ariane 504 rocket, and placed into a highly elliptical, 40-degree orbit that had a perigee of 838 km (521 mi) and an apogee of 112,473 km (69,887 mi). Forty minutes after being released from the Ariane upper stage, telemetry confirmed to ground stations that the spacecraft's solar arrays had successfully deployed. Engineers waited an additional 22 hours before commanding the on-board propulsion systems to fire a total of five times, which, between 10–16 December, changed the orbit to 7,365 × 113,774 km (4,576 × 70,696 mi) with a 38.9-degree inclination. This resulted in the spacecraft making one complete revolution of the Earth approximately every 48 hours.
Immediately after launch, XMM began its Launch and Early Orbit phase of operations. On 17 and 18 December 1999, the X-ray modules and Optical Monitor doors were opened, respectively. Instrument activation started on 4 January 2000, and the Instrument Commissioning phase began on 16 January. The Optical Monitor (OM) attained first light on 5 January, the two European Photon Imaging Camera (EPIC) MOS-CCDs followed on 16 January and the EPIC pn-CCD on 22 January, and the Reflection Grating Spectrometers (RGS) saw first light on 2 February. On 3 March, the Calibration and Performance Validation phase began, and routine science operations began on 1 June.
During a press conference on 9 February 2000, ESA presented the first images taken by XMM and announced that a new name had been chosen for the spacecraft. Whereas the program had formally been known as the High Throughput X-ray Spectroscopy Mission, the new name would reflect the nature of the program and the originator of the field of spectroscopy. Explaining the new name of XMM-Newton, Roger Bonnet, ESA's former Director of Science, said, "We have chosen this name because Sir Isaac Newton was the man who invented spectroscopy and XMM is a spectroscopy mission." He noted that because Newton is synonymous with gravity and one of the goals of the satellite was to located large numbers of black hole candidates, "there was no better choice than XMM-Newton for the name of this mission."
Because of the spacecraft's good health and the significant returns of data, XMM-Newton has received several mission extensions by ESA's Science Programme Committee. The first extension came during November 2003 and extended operations through March 2008. The second extension was approved in December 2005, extending work through March 2010. A third extension was passed in November 2007, which provided for operations through 2012. As part of the approval, it was noted that the satellite had enough on-board consumables (fuel, power and mechanical health) to theoretically continue operations past 2017. The fourth extension in November 2010 approved operations through 2014. A fifth extension was approved in November 2014, continuing operations through 2016.
The spacecraft has the ability to lower the operating temperature of both the EPIC and RGS cameras, a function that was included to counteract the deleterious effects of ionising radiation on the camera pixels. In general, the instruments are cooled to reduce the amount of dark current within the devices. During the night of 3-4 November 2002, RGS-2 was cooled from its initial temperature of −80 °C (−112 °F) down to −113 °C (−171 °F), and a few hours later to −115 °C (−175 °F). After analysing the results, it was determined the optimal temperature for both RGS units would be −110 °C (−166 °F), and during 13–14 November, both RGS-1 and RGS-2 were set to this level. During 6–7 November, the EPIC MOS-CCD detectors were cooled from their initial operating temperature of −100 °C (−148 °F) to a new setting of −120 °C (−184 °F). After these adjustments, both the EPIC and RGS cameras showed dramatic improvements in quality.
On 18 October 2008, XMM-Newton suffered an unexpected communications failure, during which time there was no contact with the spacecraft. While some concern was expressed that the vehicle may have suffered a catastrophic event, photographs taken by amateur astronomers at the Starkenburg Observatory in Germany and at other locations worldwide showed that the spacecraft was intact and appeared on course. A weak signal was finally detected using a 35-metre (115 ft) antenna in New Norcia, Western Australia, and communication with XMM-Newton suggested that the spacecraft's Radio Frequency switch had failed. After troubleshooting a solution, ground controllers used NASA's 34 m (112 ft) antenna at the Goldstone Deep Space Communications Complex to send a command that changed the switch to its last working position. ESA stated in a press release that on 22 October, a ground station at the European Space Astronomy Centre (ESAC) made contact with the satellite, confirming the process had worked and that the satellite was back under control.
The spacecraft weighs 3,800 kilograms (8,400 lb), is 10 metres (33 ft) long and 16 metres (52 ft) in span with its solar arrays deployed. It holds three X-ray telescopes, developed by Media Lario of Italy, each of which contains 58 Wolter-type concentric mirrors. The combined collecting area is 4,425 cm2 (686 sq in) at 1.5 keV to 1,740 cm2 (270 sq in) at 8 keV. The three European Photon Imaging Cameras (EPIC) are sensitive over the energy range 0.2 keV to 12 keV. Other instruments onboard are two reflection grating spectrometers which are sensitive below ~2 keV, and a 30 centimetres (12 in) diameter Ritchey-Chretien optical/UV telescope.
Each telescope consists of 58 600 mm-long shells, with diameters from 306 to 700 millimetres, and thickness linearly dependent on the diameter increasing from 470 µm at the small shells to 1070 µm at the large one; the fully assembled telescope has gaps of about one millimetre between the shells. The shells are made by electroforming onto a highly polished aluminium mandrel, starting with a 250 nm layer of vapour-deposited gold that becomes the reflecting surface, then the nickel support; the mandrels are reusable but a different one is needed for each shell. The electroforming deposits nickel at a rate of 10 µm per hour. The mandrels were manufactured at Carl Zeiss AG, and the electroforming and final assembly performed at Media Lario; Kayser-Threde also played a role.
The shells are glued into grooves in an Inconel spider, which keeps them aligned to within the five-micron tolerance required to get adequate X-ray resolution.
Observations and discoveries
The object SCP 06F6, discovered by the Hubble Space Telescope (HST) in February 2006, was then observed by XMM-Newton in early August 2006, and appeared to show an X-ray glow around it two orders of magnitude more luminous than that of supernovae. In June 2011, a team from the University of Geneva, Switzerland, reported XMM-Newton seeing a flare that lasted four hours at a peak intensity of 10,000 times the normal rate, from an observation of Supergiant Fast X-Ray Transient IGR J18410-0535, where a blue supergiant star shed a plume of matter that was partly ingested by the smaller neutron star with the accompanying X-ray emissions.
In February 2014, different analyses have extracted from the spectrum of X-ray emissions observed by XMM-Newton, a monochromatic signal around 3.5 keV. This signal is coming from different galaxy cluster, and several scenarios of dark matter can justify such a line. For example a 3.5 keV candidate annihilating into 2 photons, or a 7 keV dark matter particle decaying into photon and neutrino. In any case, it would be a warm dark matter that could be motivated also by other astrophysical observations (core galactic profiles and missing of small structures around the Milky Way).
In February 2013 it was announced that the XMM-Newton space observatory along with NuSTAR have for the first time measured the spin rate of a supermassive black hole, by observing the black hole at the core of galaxy NGC 1365. At the same time, it verified the model that explains the distortion of X-rays emitted from a black hole.
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|Wikimedia Commons has media related to XMM-Newton.|
- XMM-Newton website by ESA
- XMM-Newton Operations website by ESA
- XMM-Newton Science Operations Centre website by ESA
- XMM-Newton Survey Science Centre website by the L'Institut de Recherche en Astrophysique et Planétologie
- XMM-Newton Guest Observer Facility website by NASA/Goddard Space Flight Center