National Aeronautics and Space Administration

IXPE

The Imaging X-ray Polarimetry Explorer (IXPE) mission launched on December 9, 2021 on a SpaceX Falcon 9 rocket from NASA’s Kennedy Space Center in Florida into an equatorial orbit at 540 km altitude. The payload consists of three grazing incidence telescopes developed at NASA/MSFC each focusing on X-ray polarization detectors provided by the Italian Space Agency (Agenzia Spaziale Italiana; ASI) The spacecraft bus is from Ball Aerospace.

The observatory operates in pointing mode observing known targets for multiple (but not necessarily consecutive) orbits, requiring precise and stable pointing. The IXPE mission improves polarization sensitivity by two orders of magnitude over the X-ray polarimeter experiment on the OSO-8 satellite. Recent polarimetry with Polar focused only on gamma-ray bursts while PolarLight, with an IXPE type of detector had a limited area.

Mission Characteristics

Lifetime

Energy Range

Special Features

Payload

• The Mirror Module Assemblies (MMA) consist of three grazing incidence mirrors of Wolter-I type with 24 shells of nested parabolic and hyperbolic sections, with diameter ranging from 165 to 277 mm. The MMA is mounted on an extendable boom, deplay in orbit to reach 4m focal lenght, and equipped with laser meteorology tracking to correct for motion, tip, and tilt deflections of the MMA.
  Field-of-View (FoV) of 12.9 arcmin² square;
  Angular resolution (HPD) ~ 28 arcsec;
  Effective area per module at 166 cm² at 2.3 keV and 175 cm² at 4.5 keV.
• The Detector Units (DU) are three Gas Pixel Detector (GPD) arrays each located at the focus of one mirror. Each GPD provides position, energy, timing and polarization information for each event. The GPD images the photoelectron tracks produces by the x-rays absorbed in the special fill gas and from its initial emission direction is determined the polarization of the source. The initial interaction point and the total charge in the track provide the location and energy of the absorbed x-ray, respectively. Sensitive area 13 x 13 arcmin
  Spatial resolution (FWHM)≤ 123 µm (6.4 arcsec) @ 2 keV
  Energy resolution (FWHM) 0.57 keV @ 2 keV (∝ √E)
  Useful energy range 2 - 8 keV
  

IXPE elements have heritage : the MMA is based directly on that ART-XC launched on SRG, the deployable boom is a shorter version of that used by NuSTAR, and the GPD was flown on Polarlight.

Science Goals

• Enhance our understanding of the physical processes that produce X-rays from and near compact objects such as neutron stars and black holes.
• Explore the physics of gravity, energy, electric and magnetic fields at their extreme limits.

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