Key capabilities

Discover what makes the X-IFU so revolutionary

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The key capabilities of X-IFU lie in its unprecedented spectral resolution, better than 2.5 eV up to 7 keV, combined with a large effective area, over a 5 arcminute (the equivalent diameter) hexagonal field of view and a low instrumental background. In addition, thanks to the defocussing capability of the telescope, the X-IFU will be able to observe the brightest X-ray sources of the sky, with micro-second time resolution, and yet keeping its excellent spectral resolution.

Instrument capabilities

Before Athena and the X-IFU spectrometer, the Japanese mission XRISM and its instrument Resolve will open the window of spatially-resolved high-resolution X-ray spectroscopy. Resolve may be considered as a pathfinder to the Athena X-IFU. The main performance parameters of the two instruments are shown in the table below:


 Athena X-IFUXRISM Resolve
Spectral resolution2.5 eV5 eV
Pixel size5 arcsec1 arcmin
1 keV effective area ~8200 cm2~220 cm2
7 keV effective area~970 cm2~230 cm2
Maximum source intensity1 Crab0.2 Crab


The X-IFU combines unprecedented capabilities, that are compared below with that of the Resolve spectrometer:

  • an improved spectral resolution, around 2 times better;
  • a better spatial resolution, around 10 times smaller pixel size for imaging versus Resolve;
  • an effective area around 40 times higher at 1 keV and 4 times at 7 keV;
  • and the ability to observe very bright sources with intensities about 5 times larger (expressed in units of the X-ray flux of the Crab Nebulae).

Thanks to the spacecraft agility, X-IFU will also have the capability to respond quickly, within a few hours, to target of opportunities, discovered with other facilities on the ground or in space.

For more information, check out this publication.

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