PROBA-3, the ‘impossible mission’ to eclipse the Sun led by Spain

And to get ahead of these phenomena, you have to know them. But having to wait for eclipses is not very efficient. So scientists have come up with a way to study the elusive solar corona: coronagraphs. These tools block the light from the solar disk – in the same way that our Moon blocks the brightness of the Sun – to be able to see the corona in detail; However, they have the drawback that this system is ‘clouded’ by the phenomenon of light diffraction or how the rays bend as they pass through the atmosphere, so some detail can be lost.

But what if the best of both methods, natural and technological, could be merged? That is the idea that was raised in 2008 by officials from the Spanish space industry meeting with representatives of the European Space Agency (ESA), who outlined the ‘crazy’ possibility of building two ships that, in perfect synchrony, would create artificial eclipses on demand, far apart. of the influence of our atmosphere. “So formation flight was not viable and in space it is not improvised,” Juan Carlos Cortés, current president of the Spanish Space Agency, explained at a press conference at the European Space Astronomy Center (ESAC).

Cortés knows this first-hand because he was present at that meeting, on that occasion as director of Aeronautics and Space of the CDTI, and has been involved in the entire process. Because that idea that seemed impossible gained ESA approval in 2013 with the materialization of the Proba-3 mission. And just one year later, the space agency appointed the Spanish company Sener as the main contractor, leading a consortium of European companies from ten different countries. “It has been 16 years of hard work, but we have achieved it,” said Cortés.

Two twin ships

Because the day has come. The mission named PROBA-3 will finally be launched this Wednesday at 11:38 AM (Spanish time) on the PSLV-XL rocket of the Indian Space Research Organization (ISRO). Two satellites will travel on it: the Coronagraph, which will be in charge of taking images of the solar corona; and the Occulter, which will act as a ‘moon’ and cover, just as our satellite does, the surface of our star.

Furthermore, each one acts independently, calculating its position and trajectory with respect to its ‘twin’, moving away and closer between 25 and 250 kilometers as needed (and with millimeters of precision). And all this working as a single optical instrument, composing a virtual structure in space that can also be recalibrated, without the support of a human operator, in an elliptical orbit and at a maximum distance of 60,000 kilometers from us.

Technology demonstration

If all goes as planned, the flight formation will continue for up to six hours at a time, allowing scientists to conduct hours of uninterrupted coronal observations (an advantage considering that a solar eclipse lasts only 10 hours on Earth). minutes). In addition, at the end of the two years that the mission will initially last, the probes will be put to the limit to determine how far apart two ships in formation can safely remain.

“This milestone requires a great effort in many areas, from mission analysis to guidance, navigation and control algorithms,” said Diego Rodríguez, director of Space and Science at Sener, at the meeting. «Spain has played a fundamental role in the design, integration and testing of these systems. This mission has been led by Sener, but we could not have reached this point without the support of the participating industry and, most especially, the central team, made up of top-level Spanish companies.

Specifically, from the peninsula, Airbus Defense and Space has carried out the design and manufacturing of the two platforms; For its part, the Spanish GMV has developed the formation flight subsystem, flight dynamics and the relative GPS function; and Deimos has been responsible for the orbit analysis and the development of the final rendezvous experiment. A mission led by Spaniards that may be less impossible than it seemed.