The team’s task has not been easy. In recent months, the Satlantis company has been developing a camera to photograph the dark matter existing in the universe. In fact, there are four high-precision devices that complement each other, two of them with infrared light, on board a 300-kilogram satellite. These cameras will observe the structures around small galaxies to study the distribution of this matter, which, by the way, is invisible.
The project is called ARRAKIHS (Analysis of Resolved Remnants of Accreted Galaxies as a Key Instrument for Halo Surveys). This is the first scientific mission of the European Space Agency (ESA) coordinated and led by Spain. It also has another peculiarity: “We are used to scientists defining the challenge and then consulting the industry. But, in this case, we are working hand in hand from the beginning,” explains Juan Tomás Hernani, founder and CEO of Satlantis, the company responsible for the central components of the satellite system —the so-called payload— and the development of the cameras.
This company based in Leioa (Bizkaia) is not starting from scratch. The firm has a decade of experience in observing the Earth through these devices. For example, in detecting methane leaks or in evaluating spectral traces of fires. Now, its cameras will turn 180 degrees and focus on “nearby” galaxies, located between 82 and 130 million light years away.
“We must place the satellite far enough from Earth so that the light from the albedo does not bother us. The chosen point is 800 kilometres from the surface, in a high orbit so that we can correct the spin and always look at the same star, always with our back to the Sun,” explains this director, who was previously Secretary of State for Innovation (2009-2012).
Camera resolution
The cameras’ optics are “super-precise” due to their lenses with a tolerance of one micron and 40 nanometers of roughness. “If these same cameras were placed 500 kilometers from our planet to observe it, they would provide us with a resolution of 80 centimeters per pixel. We could recognize, for example, a car or fruit trees,” says Hernani.
The Head of Project of ARRAKIHS At ESA, Carlos Corral van Damme adds that “the key to this precision will be in the planning.” From the agency’s main centre for satellite development, located in Holland, where he speaks to EL PAÍS, Van Damme explains that “the mission will have to accumulate 150 hours of observation in at least 75 nearby galaxies to learn about the structures in the halo with very low surface brightness.” The process would be more or less similar to that which occurs in a photograph with a very long exposure in order to be able to “obtain a small number of photons.” Only that, in this case, we are talking about 900 exposures per galaxy of 10 minutes each.
The lack of knowledge about dark matter equally astonishes and excites the scientific community, says this Spaniard of Belgian descent. It also excites another of his fellow mission members, Rafael Guzmán, who has returned to Spain as leader of the consortium responsible for ARRAKIHS. After three decades of professional experience in California and Florida (United States), “Dark matter reflects the ignorance of what we do not yet know about the universe,” says Guzmán.
So far, science knows of its existence “because it responds to the laws of gravity.” This astrophysicist, who is also a research professor at the Institute of Physics of Cantabria (IFCA), adds: “We cannot see it, but we can study the effect it has on elements composed of atoms or molecules.” In other words, these scientists will infer the properties of dark matter from its interaction with objects of normal matter.
If all goes according to plan, they could obtain results that contradict empirical evidence. Currently, standard cold dark matter models predict that galactic halos should have a much more clumpy structure than observed. “If they are correct, 95% of the universe is in an unknown form and only 5% corresponds to all the planets, stars or galaxies detected,” Guzmán stresses. In the same way, dark matter would also allow us to determine, firstly, the age of the universe and, secondly, its future, that is, “whether it will always expand or there will come a time when it collapses on itself.”
The ARRAKIHS mission consortium is currently made up of five countries. Switzerland and Sweden are largely focused on the theoretical part, including the models whose predictions will be tested on this mission. The work of Austria and Belgium is linked to different instrumentation systems. The leadership of all this work falls on Spain. This international group is made up of 120 professionals divided into three areas: on the one hand, astrophysicists, physicists and mathematicians; on the other hand, the community of engineers from a wide variety of fields; and finally, the scientists and managers who coordinate the work.
ARRAKIHS is part of one of the class missions Fast ESA. These projects are characterised by a “low” budget and the fact that no more than 10 years pass between selection and launch, as specified by this project manager. In fact, last March an important milestone was reached: ESA approved the completion of Phase A, consisting of a review of the photographic instruments.
The team is now working to pass Phase B in the first half of 2026. To do so, they will have to make prototypes of the equipment and validate whether it would work in the extreme conditions of the thermosphere, such as temperatures of up to 120 below zero. The starting point is that Satlantis’ cameras have already been validated in space. The satellite is scheduled to launch in 2030.
![Simulation of a stellar stream in the halo of a galaxy, in an image from the ARRAKIHS Consortium.](https://imagenes.elpais.com/resizer/v2/ZE4EWFGPQFAODLQ7KJA74V4F4A.jpg?auth=26bc08a61b5adf079805fcfdf73b0122daface1bfcb10d4077ab46ab55aa75f9&width=414)
Van Damme is also looking forward to this horizon, without losing sight of the project’s accounts. “The ESA budget allocated to ARRAKIHS “The total cost is 200 million euros for the construction of the satellite and the preparation of the ground segment, the launch and the operations of the mission,” he reveals. However, to this amount must be added the financing for the development of the instrument “which is the responsibility of Spain and other countries,” and various “additional costs” which will be assumed by the other consortia. For this reason, Van Damme does not dare to give a final figure, much less at this stage of the mission.
What is clear is that “there has been a clear desire for growth and involvement of Spain in the space sector”. For some years now, he has perceived a “more leading and active role in many missions, from contributions to leadership areas”, as is the case of ARRAKIHS.
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