ARRAKIHS (Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys) is the second ESA fast-class mission. It was selected in 2022 and is expected to launch in 2030. The mission will explore the nature of dark matter by observing the ultra-low surface brightness galactic halo and stellar streams for a representative sample of Milky Way-type galaxies in the nearby universe. These observations will be used to test the predictions from different dark matter models and baryon physics mechanisms on these large-scale structures, and assess with statistical significance weather the reported tensions are the result of selection effects and/or small number statistics.
The mission scientific payload is a single instrument consisting of four identical two-mirrors telescopes. Each telescope provides high-precision photometry of the same relatively large (1°) part of the sky, each in a different wavelength band, from the visible to the near-infrared.
ARRAKIHS is developed by an international scientific consortium led by the Institute of Physics of Cantabria (IFCA) in Spain. The IWF is leading the development of the EBOX, the main electronics sub-system which collects the scientific observations from the four imaging sensors, communicates with the spacecraft and maintains the telescopes at their optimal temperature. The institute provides the Common Data Processing Unit (CDPU) and the EBOX housing. The IWF is in charge of integrating the other units inside the EBOX (e.g., the Power Supply Unit, provided by consortium partners), and of conducting the required environmental tests (e.g., vibration, thermal-vacuum etc.).
While the immediate scientific goals of the mission do not align well with those of the institute, IWF scientists are investigating secondary science goals for which the ARRAKIHS instrument would be suitable. Given the high-precision photometric capabilities of ARRAKIHS, the instrument can be used to collect multi-band photometric transit observations of already known transiting exoplanets, in a similar fashion to what currently done by CHEOPS, and thus extending CHEOPS' legacy beyond the 2030s.
More information is found at the ARRAKIHS Mission Consortium website.
