The most important characteristics of XMM are compiled in Table 1. More detailed numbers will follow in the chapters on the individual instruments (below) and a comparison with other X-ray satellites is provided in § 3.7. The basic characteristics of XMM are:
|Instrument||EPIC MOS||EPIC pn||RGS||OM|
|Bandpass||0.1-15 keV||0.1-15 keV||0.35-2.5 keV1||160-600 nm|
|Orbital target vis.2||5-145 ks||5-145 ks||5-145 ks||5-145 ks|
|Field of view (FOV)||30' 5||30' 5||17' 6|
|PSF ( FWHM/HEW)7||6''/15''||6''/15''||N/A|
|Pixel size||40 m (1.1'')||150 m (4.1'')||81 m ( Å)14||0.5'' 8|
|Timing resolution9||1 ms||0.03 ms||16 ms||50 ms|
|Spectral resolution10||57 eV||67 eV||0.04/0.025 Å11||0.5/1.0 nm12|
If not prohibited by target brightness constraints, all six XMM science instruments operate simultaneously. They work independently (i.e., exposures of the individual instruments do not necessarily start and end at the same time).
XMM carries the X-ray telescopes with the largest effective area of a focussing telescope ever: the total mirror geometric effective area at 1 keV energy is ca. 1550 cm2 for each telescope, i.e., 4650 cm2 in total.
XMM's high sensitivity is achieved by using 58 thin nested mirror shells in each X-ray telescope. The achieved point-spread function (PSF) has a full width at half maximum (FWHM) on the order of 6'' and a HEW, at which 50% of the total energy are encircled, of ca. 15''.
The EPIC CCD cameras have moderate spectral resolution (with a resolving power, E/E, of ca. 20-50). The RGS spectrometers offer much higher spectral resolution, with a resolving power in the range of 200-800.
Observations with the co-aligned OM optical/UV telescope render possible the monitoring and identification of X-ray sources seen by the X-ray telescopes as well as imaging of the surrounding field.
A highly elliptical orbit offers continuous target visibility of up to more than 40 hours, with a minimum height for science observations of 40,000 km. This is very favourable for studies of source variability and also in order to achieve a high overall observatory efficiency. Due to the required off time near perigee and the telemetry gap near apogee, combined with the absence of onboard data storage devices, these 40 hours will be split into two visibility periods of ca. 70 ks each, with a short gap (of order one hour) in between.
For a comparison of these basic characteristics with those of other past or contemporaneous X-ray satellite missions, see § 3.7.
More detailed information on the mirrors and on the instruments listed in Table 1 and their observing modes is provided in the following sections (§§ 3.2-3.5).