National Aeronautics and Space Administration

IXPE

The Imaging X-ray Polarimetry Explorer (IXPE) mission is planned to be launched in April 2021 into an equatorial orbit at 540 km altitude with an initial two year mission span. The X-ray polarization detectors are to be provided by the Italian Space Agency (Agenzia Spaziale Italiana; ASI) with grazing incidence optics from NASA/MSFC and the core spacecraft bus from Ball Aerospace. Launch is intended to be aboard a Pegasus XL “winged rocket” suitable for small payload missions.

Observations will consist of pointed observations at known targets for multiple (but not necessarily consecutive) orbits, requiring precise and stable pointing. The IXPE mission will by orders of magnitude on previous heritage polarimetry measurements by OSO-8: recent polarimetry with Polar focused only on gamma-ray bursts while PolarLight had a limited suite of targets.

Mission Characteristics

Lifetime

Energy Range

Special Features

Payload

• The Mirror Module Assemblies (MMU) consist of a rack of three grazing incidence mirrors of Wolter-I type with 24 shells of nested parabolic and hyperbolic sections, each 300 mm in diameter, with a packing design to reduce stray X-ray radiation from single reflections off the hyperbolic surface by more than 2.5 orders of magnitude, reducing contamination from bright sources immediately out of the field of view when imaging faint extended structures. The MMU is mounted on an extendable boom and equipped with laser meteorology tracking to correct for motion, tip, and tilt deflections of the MMU. Each telescope should have a 11′ Field-of-View (FoV) with a 9′ FoV common view with all three telescopes.
• The Detector Units (DU) consist of three gas pixel detector arrays to provide broad band X-ray polarimetry. Coupled to the MMU, the DUs should have 230 cm² effective area at 2.3 keV and 249 cm² at 4.5 keV. The expected spatial resolution should be <25″ over 300 x 352 pixel array

The elements of IXPE are all heritage components: the MMU is based directly on comparable pieces in the ART-XC on SRG, the deployable boom is similar (though shorter) than that on NuSTAR, and the spacecraft itself is based on the BCP-100 flight-proven architecture. The DU gas pixel detectors are proven technologies with 15 years of design and testing.

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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