The ground-based demonstrator, very similar to the one that will be launched into space, is already in operation at the OAJ. It is an iSIM-170 binocular camera built by the Spanish company Satlantis, and acquired by the Instituto de Física de Cantabria (IFCA, CSIC-UC). This camera consists of two telescopes, plus a multi-band imager, capable of observing in both the visible and near-infrared spectrum. It is fully adapted to operate on solid ground, thus achieving a high level of detail of the observed galaxies.

On the one hand, the performance of the demonstrator will be tested with real data, i.e. whether it achieves the required depth and image quality. It will also allow testing and validation of the observation and data analysis strategies, in order to optimise these mission parameters prior to launch.

‘The aim is to be as prepared as possible for the launch and, at the same time, to reduce any uncertainty,’ says Antonio Marín-Franch, researcher in charge of the OAJ and member of the ARRAKIHS Core Team. ‘It will allow us to perform a feasibility study of some critical aspects of the mission,’ says Marín-Franch.

The mission that explores the invisible

ARRAKIHS (Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys) aims to deepen our knowledge of dark matter and galaxy formation, with special interest in the Milky Way. Over three years it will observe more than seventy galaxies in the near environment similar to our own, in visible and infrared light, on board a minisatellite in low-Earth orbit (650-800 kilometres). This will overcome the challenge of obtaining deep images at such low levels of surface brightness from Earth, due to atmospheric interference. ‘The investment made by IFCA in this demonstrator makes our work much easier,’ says Biuse Casaponsa, IFCA researcher and coordinator of the mission's project office. ‘Being able to test the instrument in real conditions like those of the OAJ is key to prepare ourselves with guarantees.’

Location: OAJ

The Observatory, one of the seven astronomical Singular Scientific and Technical Infrastructures (ICTS) in the country, provides the site and the mount where the ground demonstrator is already installed. Specifically, it is located in the so-called Monitors building and the tests being carried out also involve setting up services, remote access and connectivity. This milestone in the critical review of the instrument is one of the main contributions of the Centro de Estudios de Física del Cosmos de Aragón (CEFCA), the centre that manages the observatory, to the mission at this time.

The experience of the staff and the capacity to lead and develop international projects are some of the strengths of the CEFCA teams, which, together with the exceptional sky conditions, make the OAJ the ideal place to test the ARRAKIHS mission.

With the camera installed at Javalambre, more than 100 hours of observation will be devoted to each of the study galaxies, similar to the Milky Way, thus facilitating the validation of the instrument, the scientific approach and the data analysis tools. After its launch in 2030, the ground-based demonstrator will continue to support the space-launched instrument, enabling a valuable comparison between the ground-based data and those obtained from the orbiting satellite.

"The ground-based demonstrator is very unconventional for a space mission. Having ground-based observations with the same space camera at this early stage of the mission gives us a great advantage to optimise the science instrument," shares Santiago Serrano, ARRAKIHS Instrument Manager, Science Director at Satlantis and Researcher at the Institute of Space Studies of Catalonia (IEEC) and at the Institute of Space Sciences of Barcelona.