XMM-Newton
XMM-Newton, also known as the High Throughput X-ray Spectroscopy Mission and the X-ray Multi-Mirror 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 after 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 wavelengths.
Initially funded for two years, with a ten-year design life, the spacecraft remains in good health and has received repeated mission extensions, most recently in March 2023 and is scheduled to operate until the end of 2026. ESA plans to succeed XMM-Newton with the Advanced Telescope for High Energy Astrophysics, the second large mission in the Cosmic Vision 2015–2025 plan, to be launched in 2035. XMM-Newton is similar to NASA's Chandra X-ray Observatory, also launched in 1999.
As of May 2018, close to 5,600 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 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. 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 in Noordwijk, Netherlands. Prime contractor Dornier Satellitensysteme 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 School of Physics and Astronomy 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 transport ship MN Toucan. The Toucan docked at the French Guianese town of Kourou on 23 September, and was transported to Guiana Space Centre 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 5 rocket, and placed into a highly elliptical, 40-degree orbit that had a perigee of and an apogee of. 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 and 16 December, changed the orbit to 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 attained first light on 5 January, the two European Photon Imaging Camera MOS-CCDs followed on 16 January and the EPIC pn-CCD on 22 January, and the Reflection Grating Spectrometers 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 locate large numbers of black hole candidates, "there was no better choice than XMM-Newton for the name of this mission."
Including all construction, spacecraft launch, and two years of operation, the project was accomplished within a budget of .
Operation
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 down to, and a few hours later to. After analysing the results, it was determined the optimal temperature for both RGS units would be, 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 to a new setting of. 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 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 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 made contact with the satellite, confirming the process had worked and that the satellite was back under control.
Mission extensions
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 to theoretically continue operations past 2017. The fourth extension in November 2010 approved operations through 2014. A fifth extension was approved in November 2014 and affirmed in November 2016, continuing operations through 2018. A sixth extension was approved in December 2017, continuing operations through the end of 2020. A seventh extension was approved in November 2018, continuing operations through the end of 2022. An eighth extension was approved in March 2023, continuing operations through the end of 2026, with indicative extension up to 2029.Spacecraft
XMM-Newton is a long space telescope, and is wide with solar arrays deployed. At launch it weighed. The spacecraft has three degrees of stabilisation, which allow it to aim at a target with an accuracy of 0.25 to 1 arcseconds. This stabilisation is achieved through the use of the spacecraft's Attitude & Orbit Control Subsystem. These systems also allow the spacecraft to point at different celestial targets, and can turn the craft at a maximum of 90 degrees per hour. The instruments on board XMM-Newton are three European Photon Imaging Cameras, two Reflection Grating Spectrometers, and an Optical Monitor.The spacecraft is roughly cylindrical in shape, and has four major components. At the fore of the spacecraft is the Mirror Support Platform, which supports the X-ray telescope assemblies and grating systems, the Optical Monitor, and two star trackers. Surrounding this component is the Service Module, which carries various spacecraft support systems: computer and electric busses, consumables, solar arrays, the Telescope Sun Shield, and two S-band antennas. Behind these units is the Telescope Tube, a long, hollow carbon fibre structure which provides exact spacing between the mirrors and their detection equipment. This section also hosts outgassing equipment on its exterior, which helps remove any contaminants from the interior of the satellite. At the aft end of spacecraft is the Focal Plane Assembly, which supports the Focal Plane Platform and the data-handling, power distribution, and radiator assemblies.