X-ray Multi-mirror Mission (XMM-Newton) has been one of the most successful astronomy missions launched by the European Space Agency. The mission exploits innovative use of replication technology for the x-ray reflecting telescopes that has resulted in an unprecedented combination of effective area and resolution. Three telescopes are equipped with imaging cameras and spectrometers that operate simultaneously, together with a coaligned optical telescope. The key features of the payload are described, and the in-orbit performance and scientific achievements are summarized.
Since December 1999, ESA's large X-ray space observatory XMM-Newton operates in a highly eccentric 48-h orbit which allows for long uninterrupted exposure times. The three payload instruments EPIC, RGS, and OM yield scientific data of high quality and sensitivity. We report here on the current timing capabilities of all three instruments by showing results from analyses on relative and absolute timing. In this context we discuss the process of correlating local onboard event arrival times to terrestrial time frames and present some detailed results from time correlation analyses. This involves investigations on the performance of the onboard quartz oscillator that have been performed. In addition we describe problematic timing data anomalies in the EPIC-pn data and their treatment by the SAS. We show recent examples of timing analyses.
The high throughput x-ray spectroscopy mission (XMM) is a 'Cornerstone' Project in the ESA long-term Program for Space Science. The satellite observatory uses three grazing incidence mirror modules coupled to reflection grating spectrometers and x-ray CCD cameras. Each XMM mirror module consists of 58 Wolter I mirrors which are nested in a coaxial and confocal configuration. The calibration of the mirror system includes the development of a representative numerical model and its validation against extensive calibration test performed on ground at the CSL and PANTER test facilities. The present paper describes the calibration of the x-ray image quality of the first XMM flight mirror module.
The High Throughput X-ray Spectroscopy Mission (XMM) is a "Cornerstone" Project in the ESA long-term Programme for Space Science. The satellite observatory uses three grazing incidence mirror modules coupled to reflection grating spectrometers and X-ray CCD cameras. Each XMM mirror module consists of 58 Wolter I mirrors which are nested in a coaxial and cofocal configuration. The calibration of the mirror system includes the development of a representative numerical model and its validation against extensive calibration tests performed on ground at the CSL and PANTER test facilities. The present paper describes the calibration of the x-ray effective area of the first XMM flight mirror module.
Keywords: XMM, X-ray astronomy, Wolter I telescope, grazing incidence optics
We describe simulations of the XMM EPIC instruments which suggests the correct operating mode must be chosen to ensure that spectral analysis of the data is not compromised by 'pile-up' effects. We contrast the performance with the AXAF CCD imaging spectrometer, and show that the XMM EPIC instruments will access a larger range of source fluxes due to a combination of higher effective area and better over- sampling of its mirror response function. Targets exceeding a flux of a few 10<SUP>-12</SUP> ergs cm<SUP>-2</SUP>s<SUP>-1</SUP> will be compromised for spectral analysis in AXAF. For XMM, the corresponding flux levels will be 10<SUP>-11</SUP> ergs cm<SUP>-11</SUP> ergs cm<SUP>-2</SUP>s<SUP>-1</SUP>. This feature warrants careful attention in calibration.
Arrays of superconducting tunnel junctions (STJs) provide the possibility to perform high-resolution imaging spectrophotometry at x-ray wavelengths. We describe the applications of STJ arrays to x-ray astronomy, and present measurements on a 3 by 3 test array of Nb/Al-based STJs, operated at a temperature of 1.2 K, which illustrate the current photometric and spectroscopic capabilities of such devices. These results demonstrate the basic experimental feasibility of STJ arrays and indicate that there are no fundamental problems to be expected in the development of large-format x-ray detector arrays based on STJs.
ESA is undertaking an extensive program aimed at the fabrication of high quality superconducting tunnel junctions, based on Nb, to be used for the detection of radiation from infrared to gamma ray wavelengths. To extend our knowledge of current technology, devices have been manufactured using an alternative technology, consisting of epitaxial Nb bottom electrode film, and a variety of materials and layouts for the tunnel layers as well as the top film. A specific mask set has been designed to enable optimized fabrication, diagnostics and testing of these devices which also includes the first 3 by 3 Nb superconducting tunnel junction test array. Preliminary results are presented on the performance of various types of devices where the tunnel barrier characteristics and device size have been systematically varied.
X-ray calibration of the Electro-Optical Breadboard Model (EOBB) of the XMM Reflection Grating Spectrometer has been carried out at the Panter test facility in Germany. The EOBB prototype optics consisted of a four-shell grazing incidence mirror module followed by an array of eight reflection gratings. The dispersed x-rays were detected by an array of three CCDs. Line profile and efficiency measurements were made at several energies, orders, and geometric configurations for individual gratings and for the grating array as a whole. The x-ray measurements verified that the grating mounting method would meet the stringent tolerances necessary for the flight instrument. Post EOBB metrology of the individual gratings and their mountings confirmed the precision of the grating boxes' fabrication. Examination of the individual grating surface's at micron resolution revealed the cause of anomalously wide line profiles to be scattering due to the crazing of the replica's surface.
The Reflection Grating Spectrometer (RGS) onboard the ESA satellite XMM (X-ray Multi Mirror mission) combines a high resolving power (approximately 400 at 0.5 keV) with a large effective area (approximately 200 cm<SUP>2</SUP>). The spectral range selected for RGS (5 - 35 angstroms) contains the K shell transitions of N, O, Ne, Mg, Al, Si and S as well as the important L shell transitions of FE. The resolving power allows the study of a wide variety of challenging scientific questions. Detailed temperature diagnostics are feasible as the ionization balance is a unique function of the distribution of the electron temperature. Density diagnostics are provided by studying He-like triplets where the ratio of the forbidden to intercombination lines varies with density. Other fields of interest include the determination of elemental abundances, the study of optical depth effects, velocity diagnostics by measuring Doppler shifts and the estimate of magnetic fields through the observation of Zeeman splitting. The resolving power is obtained by an array of 240 gratings placed behind the mirrors of the telescope, dispersing about half of the X-rays in two spectroscopic orders. The X-rays are recorded by an array of 9 large format CCDs. These CCDs are operated in the frame transfer mode. They are back illuminated as the quantum efficiency of front illuminated devices is poor at low energies because of their poly-silicon gate structure. To suppress dark current the CCDs are passively cooled. In order to obtain the effective area of about 200 cm<SUP>2</SUP>, grating arrays and CCD cameras are placed behind two of the three XMM telescopes. A model of RGS was tested last autumn ('93) at the Panter long beam X-ray facility in Munich. The model consisted of a subset of four mirrors, eight representative gratings covering a small section of the inner mirror shells and a CCD camera containing three CCDs. The purpose of these tests was to verify the resolution and sensitivity of the instrument as a function of X-ray energy. Extensive simulations, using a Monte Carlo raytracing code, are used to interpret these tests. Preliminary results of these tests will be discussed and compared to the calculated response.
The European Space Agency X-ray Multi-Mirror mission will be devoted to X-ray imaging and spectroscopy with high throughput. Both the EPIC focal plane camera instrument, and the RGS dispersive spectrometer require detectors with high sensitivity in the soft X-ray waveband. A description of