Imaging X-ray Polarimetry Explorer

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Imaging X-ray Polarimetry Explorer
Imaging X-ray Polarimetry Explorer.jpg
Artist's impression of IXPE. On the right are its three identical X-ray telescopes
Mission typeX-ray astronomy satellite
OperatorNASA / Italian Space Agency
Mission duration2 years (planned)
Spacecraft properties
ManufacturerBall Aerospace[1]
Launch mass~320 kg (710 lb)[1]
Payload mass170 kg (370 lb)[1]
Start of mission
Launch dateApril 2021[1]
RocketPegasus XL[2][3]
Launch siteKwajalein Atoll[4]
ContractorNorthrop Grumman
Orbital parameters
Reference systemgeocentric
Periapsis540 km[1]
Apoapsis540 km
Inclination0° (Equatorial)
Focal length4 m [4]
BandS band [5]

The Imaging X-ray Polarimetry Explorer (IXPE) is a future space observatory with three identical telescopes designed to measure the polarization of cosmic X-rays.[6] The mission will study exotic astronomical objects and permit mapping the magnetic fields of black holes, neutron stars, pulsars, supernova remnants, magnetars, quasars, and active galactic nuclei. The high-energy X-ray radiation from these objects' surrounding environment can be polarized – vibrating in a particular direction. Studying the polarization of X-rays reveals the physics of these objects and can provide insights into the high-temperature environments where they are created.[3]


The IXPE mission was announced on January 3, 2017.[6] It is being developed by NASA's Small Explorer program (SMEX) and is slated for launch in April 2021.[2] The estimated cost of the mission and its two-year operation is $188 million.[3] The goal of the IXPE mission is to expand understanding of high-energy astrophysical processes and sources, in support of NASA's first science objective in astrophysics: "Discover how the universe works."[1] By obtaining X-ray polarimetry and polarimetric imaging of cosmic sources, IXPE addresses two specific science objectives: to determine the radiation processes and detailed properties of specific cosmic X-ray sources or categories of sources; and to explore general relativistic and quantum effects in extreme environments.[1][6]

During IXPE's two-year mission, it will study targets such as active galactic nuclei, quasars, pulsars, pulsar wind nebulae, magnetars, accreting X-ray binaries, supernova remnants, and the Galactic center.[4]

The spacecraft is being built by Ball Aerospace.[1] The Principal Investigator is Martin Weisskopf of NASA Marshall Space Flight Center; he is the chief scientist for X-ray astronomy at NASA's Marshall Space Flight Center and project scientist for the Chandra X-Ray Observatory spacecraft.[3]

International collaboration[edit]

The IXPE mission is an international collaboration signed on June 2017.[1] The X-ray polarization detectors will be provided by the Italian Space Agency (ASI).[3] Brian Ramsey is leading the effort to produce the grazing-incidence X-ray mirrors at NASA/MSFC. Other partners include the University of Colorado at Boulder, Stanford University, McGill University in Canada, and MIT (Massachusetts Institute of Technology).[1]


The technical and science objectives include: [7]

  • improving polarization sensitivity by two orders of magnitude over the X-ray polarimeter aboard the Orbiting Solar Observatory 8
  • providing simultaneous spectral, spatial, and temporal measurements
  • determining the geometry and the emission mechanism of Active Galactic Nuclei and microquasars
  • finding the magnetic field configuration in magnetars and determining the magnitude of the field
  • finding the mechanism for X ray production in pulsars (both isolated and accreting) and the geometry
  • determining how particles are accelerated in pulsar wind nebula


Telescope (x3) Basic parameters
Wavelength X-ray
Energy range 2–8 keV
Field of view (FOV) >11′
Angular resolution ≤30″

The space observatory features three identical telescopes designed to measure the polarization of cosmic X-rays.[6] The system was invented and developed by Italian scientists and refined over the past 15 years by the Italian Istituto Nazionale di Fisica Nucleare (INFN).[4]


IXPE's payload is a set of three identical imaging X-ray polarimetry systems mounted on a common optical bench and co-aligned with the pointing axis of the spacecraft.[1] Each system operates independently for redundancy, and comprises a 4-meter focal length mirror module assembly that focuses X-rays onto a polarization-sensitive imaging detector developed in Italy.[1] The focal length is achieved using a deployable boom.

The Gas Pixel Detectors (GPD) utilize the anisotropy of the emission direction of photoelectrons produced by polarized photons to gauge with high sensitivity the polarization state of X-rays interacting in a gaseous medium.[4] Position- and energy-dependent polarization maps of such synchrotron-emitting sources will elucidate the magnetic field structure of the X-ray emitting regions. X-ray polarimetric imaging better indicates the magnetic structure in regions of strong electron acceleration. The system is capable to resolve point sources from surrounding nebular emission or from adjacent point sources.[4]

See also[edit]


  1. ^ a b c d e f g h i j k l m "IXPE (Imaging X-ray Polarimetry Explorer)". eoPortal. ESA. Retrieved February 17, 2019.
  2. ^ a b IXPE the Imaging X-ray Polarimetry Explorer. August 29, 2017. Proc. SPIE 10397, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX, 103970I (August 29, 2017); doi:10.1117/12.2275485
  3. ^ a b c d e NASA selects X-ray astronomy mission. Jeff Foust, Space News. January 4, 2017.
  4. ^ a b c d e f The Imaging X-ray Polarimetry Explorer (IXPE). Martin C. Weisskopf, Brian Ramsey, Stephen L. O’Dell, et al. Results in Physics. Volume 6, 2016, Pages 1179-1180. doi:10.1016/j.rinp.2016.10.021
  5. ^ IXPE Fact Sheet. NASA 2017.
  6. ^ a b c d NASA Selects Mission to Study Black Holes, Cosmic X-ray Mysteries. Karen Northon, NASA News. January 3, 2017.
  7. ^ IXPE: Expanding the X-ray View of the Universe. NASA. 2017.