Publication archive

Publication archive

The XMM satellite will be launched in August 1999 and a simulator has been developed to test and validate the supporting ground segment. Due to the very tight schedule and the high fidelity of the modelling required, this development effort has provided numerous unique challenges. This article details these challenges and the approaches that have been taken in meeting them, as well as the simulator's architecture and current status.
Published: 02 May 1998
Product Assurance has both a preventative and a corrective role in terms of quality control in a spacecraft project. This article summarises how it was approached within the XMM project, what unforeseen problems were encountered, and what lessons can be learned from our experience.
Published: 01 December 1999
The XMM (X-ray Multi-Mirror) spacecraft, a spaceborne X-ray observatory to be launched by Ariane-5, stands 10 m high and measures over 4 m in diameter in launch configuration, for a launch mass of just under four tons. Such a tall spacecraft challenges the capabilities of existing European environmental testing facilities. Provisions were made in the design for a split according to geometry into an Upper Module and a Lower Module for environmental test purposes. Optical testing of the X-ray Mirror Modules - the core technological challenge - required the use of several existing and custom-built test facilities. In the face of strict schedule requirements, spacecraft-level test flows were organised around extensively parallel flows and all tests were scrutinised for their potential for early problem identification. This article briefly introduces the XMM configuration and schedule constraints, explains the spacecraft-level model philosophy, discusses the consequences for each category of test in terms of facility and test specimen configurations, and summarises the spacecraft test flows and the results achieved.
Published: 01 December 1999
Scaling the XMM data-handling system to the specific needs of the mission has resulted in a flexible and relatively uncomplicated On-Board Data-Handling (OBDH) Subsystem. The XMM spacecraft is operated in real-time and is fully compliant with the ESA packet data-handling standards. Packets are of variable length and presented to the OBDH when available. The OBDH telemetry/telecommand cycles are asynchronous to the instrument and subsystem cycles. The telemetry rates can easily be reallocated to cope with unforeseen spacecraft configurations, e.g. lost telemetry sources. The absence of requirements for automatic reconfiguration has contributed to the reduced subsystem complexity.
Published: 01 December 1999
The XMM Electrical Power Subsystem (EPS) is 'conventional' in design in that it follows the ESA Power Standard. This article describes the subsystem's main features and performances, and the steps that have been taken in implementing the lessons learnt from the highly successful SOHO spacecraft recovery efforts, which were described in detail in ESA Bulletin No. 97.
Published: 01 December 1999
The pointing and alignment performance of the XMM spacecraft will have a very strong influence on the quality of the scientific results obtainable. The pre-launch unit and subsystem tests and subsequent analyses have shown that the scientific requirements will indeed be met with comfortable margins and the performance goals will be met for more than 90% of all anticipated observations.
Published: 01 December 1999

Attitude and orbit control of the XMM spacecraft relies on two subsystems on-board: the Attitude and Orbit Control Subsystem (AOCS) and the Reaction Control Subsystem (RCS). Together they must provide:

  • stable Sun-pointing after the spacecraft's separation from the launcher and during solar-array deployment
  • increase the spacecraft's perigee altitude by means of a chemical propulsion delta-V of about 210 ms-1
  • provide undisturbed, high-accuracy, three-axis pointing during scientific observations lasting up to 40 h
  • slew the spacecraft between observations, and before and after perigee ensure that the Sun remains more than 15 deg away from the telescope at all times.
Published: 01 December 1999
The XMM spacecraft has a conventional structure and thermal design. Due to the long focal length of the telescopes (7.5 m), the mirrors are far removed from the instruments. On the ground and during the launch, the structure has to maintain the integrity of the whole spacecraft. The thermal control does not make use of onboard software. In orbit, the functions of the structure and the thermal control are mixed. Their global common requirement is to relate and align the set of mirrors at one end of the spacecraft with the set of instruments at the other. Some parts of the instruments will be kept at cryogenic temperatures, but most of the spacecraft will be kept at about room temperature. It is the task of the thermal control to maintain these diverse requirements by passive and active means. Under inevitably varying thermal conditions, the structure has to stay very 'straight'.
Published: 01 December 1999
We recently predicted the formation of a highly non-equilibrium quasiparticle (qp) distribution in low TC multiple tunnelling superconducting tunnel junctions (STJs) [1]. The situation arises through qp energy gain in cycles of successive forward and back tunnelling events in the absence of relaxation via sub-gap phonon emission. The qps can acquire sufficient energy to emit phonons, which break more Cooper pairs and release additional qps. In this paper we report theoretical and experimental studies of the effect of this process on photon detection by such an STJ. We derived a set of energy-dependent balance equations [2], which describe the kinetics of the qps and phonons, including the qp multiplication process described above. Solution of the balance equations gives the non-equilibrium distribution of the qps as a function of time and energy, and hence the responsivity of the STJ as a function of bias voltage. We compared the theoretical results with experiments on high quality, multiple-tunnelling Al STJs cooled to 35mK in an adiabatic demagnetisation refrigerator, and illuminated with monochromatic photons with wavelengths between 250 and 1000 nm. It was found that in the larger junctions with the longest qp loss time, both responsivity and signal decay time increased rapidly with bias voltage. Excellent agreement was obtained between the observed effects and theoretical modelling.
Published: 02 May 2003
This article is based on a talk given by Professor Gerhard Beutler of the Astronomical Institute, University of Berne, to the Pro ISSI.
Published: 02 May 2003
The XMM observatory has, at its heart, three large X-ray telescopes, which will provide a large collecting area (1430 cm² each at 1.5 keV, and 610 cm² each at 8.0 keV) with a spatial resolution of around 14-15 arcsec. At the end of 1998, three months ahead of schedule, the three flight and the two spare models of the X-ray telescope were handed over to the XMM Prime Contractor Daimler Chrysler Aerospace (D). The three flight models were integrated onto the spacecraft's optical platform at ESTEC at the end of March 1999.
Published: 01 December 1999
The payload carried by the X-Ray Multi-Mirror Mission (XMM), the second Cornerstone of the ESA Horizon 2000 Science Programme, consists of three scientific instruments: the Reflection Grating Spectrometer (RGS), the European Photon Imaging Camera (EPIC), and the Optical Monitor (OM). This article provides a general overview of the main characteristics of all three instruments.
Published: 01 December 1999
The X-Ray Multi-Mirror Mission (XMM) is an X-ray astrophysics observatory scheduled for launch in December 1999. With a projected lifetime of 10 years, it will enable astronomers to conduct sensitive spectroscopic observations of a wide variety of cosmic sources.
Published: 01 December 1999
Since its launch on 2 December 1995, the Solar and Heliospheric Observatory (SOHO) has provided an unparalleled breadth and depth of information about the Sun, from its interior, through the hot and dynamic atmosphere, out to the solar wind. Analysis of the helioseismology data from SOHO has shed new light on a number of structural and dynamic phenomena in the solar interior, such as the absence of differential rotation in the radiative zone, subsurface zonal and meridional flows, sub-convection-zone mixing, a possible circumpolar jet, and very slow polar rotation. The ultraviolet imagers and spectrometers have revealed an extremely dynamic solar atmosphere in which plasma flows play an important role. Evidence for an upward transfer of magnetic energy from the Sun's surface toward the corona has been found. Electrons in coronal holes have been found to be relatively 'cool', whereas heavy ions are extremely hot and have highly anisotropic velocity distributions. The source region for the high-speed solar wind has been identified and the acceleration profiles of both the slow and fast solar wind have been measured.
Published: 02 April 2000
As the inner end-member of the planetary system, Mercury plays an important role in constraining and testing dynamical and compositional theories of planetary formation. The exploration of Mercury is of fundamental importance for answering questions of astrophysical and philosophical significance, such as: 'Are terrestrial bodies a common feature of most planetary systems in the Galaxy?'.
Published: 02 July 2000
Two years after the launch of the XMM-Newton Observatory saw a gathering of about 350 scientists at ESTEC for the Conference 'New Vision of the X-ray Universe'. This huge interest in the mission and the rapidly increasing number of scientific papers published as a result of XMM-Newton observations show the importance of ESA's latest observatory for astrophysics in the 21st century.
Published: 01 February 2002
The term 'Target of Opportunity' (ToO) is used in astronomy to identify unpredictable events whose study is of the highest scientific interest. For Xmm-Newton a ToO is an astronomical event observable by its instruments, which cannot be predicted and scheduled on the time scale of one year, yet is scientifically significant enough to justify the interruption of the ongoing observing programme. Here we discuss the kinds of objects that are suitable for observation as ToOs with XMM-Newton, their scientific interest, and how they are incorporated into the overall observing schedule in terms of target selection and mission planning. What has been done so far and the preliminary results for a few ToO examples are then presented
Published: 02 July 2001
Water, the basic substance essential for life, has been detected by the Infrared Space Observatory (ISO) in many places throughout the Universe, including our planetary neighbours in the Solar System, clouds circling or pouring out of stars, the vast spaces between stars, and distant galaxies. We show here how these observations enable us to reconstruct the cosmic cycling of water, and its relevance to the presence of water on the Earth.
Published: 01 November 2000
The XMM-Newton space observatory - a Cornerstone mission in ESA's Horizon 2000 Programme and originally referred to as the High- Throughput X-ray Spectroscopy Mission - was placed into a 48-hour orbit by the first commercial Ariane-5 launch (V504) on 10 December 1999. This brief survey of the scientific results obtained during the first year of XMM-Newton operations clearly illustrates that the observatory is more than living up to expectations and already providing unique and promising results, even before full scientific data analysis gets officially underway.
Published: 01 November 2000
Last Christmas Eve was very special one for ESA astronauts Claude Nicollier and Jean-François Clervoy: together with their American colleagues, they spent it aboard the Space Shuttle 'Discovery', after concluding the latest scheduled repair mission to the orbiting Hubble Space Telescope (HST). This third Shuttle refurbishment mission to HST was, like its two predecessors, a resounding success. Only days later, as Hubble entered the new millennium, came the first beautiful images of a complex gravitationally lensing cluster of galaxies. The astronauts' visit took place shortly before the 10th Anniversary of the launch of Hubble, which was first placed in orbit on 26 April 1990. Since then, HST has become the leading tool in ultraviolet, optical and near-infrared astronomy and is now looking forward to another decade of exciting discoveries and sharp views of the Universe.
Published: 01 November 2000
31-Oct-2020 08:25 UT

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