The Hitomi mission


Hitomi, previously known as ASTRO-H, is an international X-ray observatory led by the Japan Aerospace Exploration Agency (JAXA), in collaboration with NASA, with European and Canadian involvements. The mission has been lanched on 17 February 2016. It is part of a very successful scientific program dedicated to astrophysical exploration. Japanese missions dedicated to high-energy astrophysics include Hakucho (1979), Tenma (1983), Ginga (1987), ASCA (1993) and Suzaku (2005, after the launch failure of an identical mission in 2000), which has ended its operations in late 2015.

Like it has been the case for Suzaku, JAXA invited European astrophysicists to participate in the ASTRO-H science team and offers telescope time to the European community. In exchange, the European Space Agency encouraged European participation in the development of the scientific payload of ASTRO-H. SRON and the University of Geneva participated in the hardware development of the filter wheel for the X-ray calorimeter onboard ASTRO-H. The University of Geneva also acts as Hitomi European Science Support Centre, while ESA acts as the European Science Operations Centre for Hitomi.

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The mission objectives of Hitomi are to study the evolution of the population of obscured supermassive black holes in active galactic nuclei, trace the growth history of the largest structures in the Universe, provide insights into the behavior of material in extreme gravitational fields, determine the spin of black holes and the equation of state of neutron stars, trace particle acceleration structures in clusters of galaxies and supernova remnants and investigate the detailed physics of jets. Hitomi will achieve these goals thanks to two major technological leaps:

  • The first focussing optics telescope (HXT) in a hard X-ray observatory
  • The first high-resolution spatially resolved spectroscopy using cryogenics detector (SXS)

Hitomi has been launched by JAXA from the Tanegashima Space Center thanks to a HII-A rocket on February 17 (Wednesday), 2016. The orbit of the satellite is low Earth, i.e., at an altitude of 575 km, on an approximately circular orbit. The orbital period of Hitomi around the Earth is 96 minutes. The mission lifetime is expected to exceed 3 years.




Schematic view of the Hitomi satellite. The Hard X-ray and Soft X-ray Telescopes are placed at the top of the fixed optical bench, whereas the Soft X-ray Imager and the Soft X-ray Spectrometer are placed at the bottom of the fixed optical bench. The Hard X-ray Imagers and the Soft Gamma-ray Detector are placed on a platform placed at the 12 m focus of the HXT thanks to a deployable optical bench


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Broad-band coverage in the X-ray and gamma-ray regimes will be obtained by a suite of instruments from about 0.3 to 600 keV