Spain's Sener is the European pioneer of high-precision formation spaceflight

ESA's Proba-3 mission has put to the test the leadership, coordination and technological innovation capabilities of the national space network 
La ESA ha dado su confianza al equipo industrial y tecnológico capitaneado por Sener para sacar adelante el tremendo desafío que supone la muy compleja misión Proba-3 - PHOTO/ESA-M. Pedousat-J. Versluys
ESA has placed its trust in the industrial and technological team led by Sener to take on the tremendous challenge of the highly complex Proba-3 mission - PHOTO/ESA-M. Pedousat-J. Versluys
  1. Bigger than two domestic washing machines
  2. It will fly into space from India

"We can already see the light at the end of the tunnel, which was about time," says the director of Science and Space at Sener Aerospace and Defence, Diego Rodríguez. 

A veteran and recognised executive in the Spanish space industry, Rodríguez is responsible for the European Space Agency (ESA) having placed its trust in the project presented by Sener to take on the tremendous challenge of carrying out the highly complex Proba-3 mission against all odds.

What is so special about Proba-3? Well, a lot, both from a technological and scientific point of view. Also from the perspective of consolidating the innovation capabilities of the national industry. Proba-3 is a technological demonstration mission that aims to prove that high-precision formation flying between two satellites is possible, a pioneering initiative in Europe and one that there is no official record of having been tested in the United States, Russia or China. 

Los primeros estudios industriales se remontan a 2011, cuando el actual director de Espacio y Ciencia de Sener, Diego Rodríguez (izquierda), suscribió con la ESA el primer contrato de Proba-3 - PHOTO/ESA-Anneke L’Floch
The first industrial studies date back to 2011, when Sener's current Director of Space and Science, Diego Rodríguez (left), signed the first Proba-3 contract with ESA - PHOTO/ESA-Anneke L’Floch

For Sener, this represents a major challenge, because it is the first time that a Spanish company has led an entire ESA mission. It entails the role of prime contractor for the entire European space mission. On the one hand, the sophisticated satellites, but also the infrastructures and technologies that have to be set up on the ground to control the position and movements of the two spacecraft and receive their data. 

The company based in Tres Cantos, near Madrid, has full responsibility for specifying, designing, developing, manufacturing, positioning and delivering into orbit not one, but two twinned satellites, launched at the same time, which separate once in outer space and which are very different from each other. 

Ambos ingenios permanecen en la sede de la empresa belga Redwire cerca de Amberes, donde se practican las ultimas comprobaciones antes del inicio de la campaña de lanzamiento - PHOTO/Redwire
Both spacecraft remain at the Belgian company Redwire's headquarters near Antwerp, where final checks are being carried out before the launch campaign begins - PHOTO/Redwire

Bigger than two domestic washing machines

For Diego Rodríguez, who has led dozens of ESA space programmes, Proba-3 has meant captaining and coordinating "in time and form the work of an industrial consortium made up of almost thirty companies from 17 European nations". At its core are two Belgian companies, Redwire and Spacebel, and two Spanish companies: Airbus Space Systems España and GMV. 

Under the leadership of Enrique Fraga, GMV has developed the flight dynamics system, the formation flying subsystem - the key to the mission - and the relative GPS function, which allows the position of the two satellites to be known with a high degree of precision. The Airbus space branch in Spain, headed by Luis Guerra, has designed and manufactured the structures of the two platforms, the propulsion and thermal control systems, as well as the interior cabling. 

Both are approximately the size of a cube with a side of one metre, "and the two together have a volume of a little more than two domestic washing machines," says Rodríguez, who has seen them born and grow. They will fly in an elliptical orbit whose lowest orbit above the Earth, or perigee, will be about 600 kilometres and the highest, or apogee, will be about 60,000 kilometres. 

Con una órbita baja de 600 kilómetros y alta de 60.000, estarán alineados con el Sol para obtener durante seis horas al día continuadas imágenes de la tenue atmósfera exterior del Sol - PHOTO/ESA-P. Carril
With a low orbit of 600 kilometres and a high orbit of 60,000 kilometres, they will be aligned with the Sun for six hours a day of continuous imaging of the Sun's tenuous outer atmosphere - PHOTO/ESA-P. Carril

Pending simpler names, one is called Coronographer and the other Occulter and they will be 144 metres apart with an accuracy of the order of millimetres and seconds of arc. Each satellite will evolve independently, calculating its position and trajectory with respect to its counterpart automatically thanks to the advanced guidance, navigation and control system developed by Spanish industry.

In its scientific task, the pair will form a straight line with the Sun. The Occulter will cast a shadow on the Coronagraph, which will block the bright solar disc, and images of the faint outer atmosphere of the Astro King will be obtained for six continuous hours, something impossible from Earth, in an attempt to unravel the mysteries of the Sun's corona.

Airbus España ha diseñado y fabricado las estructuras de las dos plataformas, los sistemas de propulsión y control térmico y también el cableado - PHOTO/Redwire
Airbus Spain has designed and manufactured the structures of the two platforms, the propulsion and thermal control systems and also the cabling - PHOTO/Redwire

It will fly into space from India

Where are the two satellites now? They are at the Redwire facility in the Belgian town of Kruibeke, some 14 kilometres from the large port city of Antwerp. The final rigorous tests are being carried out there. 

When will it be launched into space? "In the second half of September or the first half of October," says Diego Rodríguez. "Whether it will be in one month or the other depends on whether we manage to finish the demanding tests by the end of June or the beginning of July". 

As ESA currently has no space transportation system available, ESA's Director of Launchers, Toni Tolker-Nielsen of Denmark, has opted to contract the services of a PSLV rocket from the Indian Space Research Agency (ISRO). The European agency wants to test the efficiency of New Delhi's vectors for itself and has ruled out Elon Musk's Falcon 9, despite its high success rate

El despegue del cohete PSLV será desde el Centro Espacial Satish Dhawan, en Sriharikota, zona costera situada en el golfo de Bengala, en el estado de Andhra Pradseh, al sureste del subcontinente indio - PHOTO/ISRO
The PSLV rocket will take off from the Satish Dhawan Space Centre in Sriharikota, a coastal area located in the Bay of Bengal, in the state of Andhra Pradseh, in the southeast of the Indian subcontinent - PHOTO/ISRO

The liftoff will take place from the Satish Dhawan Space Centre, located in Sriharikota, a coastal area on the Bay of Bengal in the state of Andhra Pradseh in the southeast of the Indian subcontinent.   

According to ESA's Director of Technology, Engineering and Quality from May 2023, Germany's Dietmar Pilz, the cost of the programme, including the launch from India, is around 200 million euros. From his point of view, Proba-3 is an "extremely technologically challenging" mission.