Juice, Europe's sophisticated lead-armoured space probe with Spanish protagonism

The technological explorer called JUICE that the European Space Agency (ESA) has just put into orbit to discover the secrets of the great gaseous planet Jupiter and its moons is full of Spanish names that have pledged their talent to make it a reality.

The first of these engineers, technicians and scientists is the astrophysicist Álvaro Giménez, who on 8 December 2015, in his capacity as ESA's Director of Science, signed the contract that opened the door to the development and construction of JUICE, an acronym for JUpiter ICy Moons Explorer. The end result is a probe weighing just under 6 tonnes at liftoff, including 3.5 tonnes of fuel to power its movements in space until the end of its mission in the 2030s.

Álvaro Giménez was already aware of the enormous challenge involved in preparing and sending a spacecraft to Jupiter to unravel the secrets of its turbulent atmosphere, its enormous magnetosphere and its dark rings, an icy environment with a very intense level of radiation and three icy moons: Ganymede, Europa and Callisto.

The fact is that it is not feasible to travel directly the 700 million kilometres on average that separate the planet from the Earth, which has required the gravitational assistance of the Earth, the Moon and Venus. This has meant defining a trajectory of more than 6 billion kilometres to reach Jupiter in eight years' time. Once there, JUICE will study the planet closely for three and a half years and will fly over Callisto 21 times, Ganymede 12 times and Europa only twice. ESA confirms that the total investment has been 1.6 billion euros.

Another of the many names on the list of national protagonists is Rosario Lorente. She belongs to the scientific team of the ESA Space Astronomy Centre (ESAC) mission located in Villanueva de la Cañada, near Madrid. From his point of view, the so-called Jovian System, headed by Jupiter, is the "archetype of the gas giant planets, a big puzzle with many pieces still to be shaped". Its understanding is "of great interest, both for understanding our Solar System and a large fraction of the planetary systems discovered in our Galaxy".

Spanish industry has had to contribute its extensive innovation capabilities to the great technological challenges represented by JUICE. The contribution of seven companies and more than a dozen researchers from the Instituto de Astrofísica de Andalucía and the Instituto Nacional de Técnica Aeroespacial (INTA) has been coordinated from the Centro para el Desarrollo Tecnológico y la Innovación (CDTI) first by Pilar Román and then by Cecilia Hernández.

It should be borne in mind that from the moment JUICE is launched into orbit on 14 April at 14:14 Spanish peninsular time by the penultimate remaining European Ariane 5 launcher until the end of its mission, the probe will be subjected to an "incessant bombardment of very high-energy and very high-speed particles", explains Rosario Lorente. They will impact and penetrate its interior, gradually damaging its internal electronic systems and equipment, which will increase as it approaches the vicinity of Jupiter.

On top of that, the European probe must survive a wide range of temperatures. It must withstand temperatures in the order of 250°C during its flyby of Venus and withstand intense cold, down to -230°C, when it approaches the vicinity of Jupiter. So the working conditions for the engineers have been very demanding.

Airbus Space Systems España had to solve one of the main technical challenges of the mission, which consisted of making the structural shielding that must protect the spacecraft's critical electronics a reality. Its engineers and technicians had to develop a system comparable to lead safes.

Successive sheets of lead weighing a total of more than 150 kilos envelop the essential electronics and its most sensitive equipment and protect them from particle radiation. This is intended to slow down the degradation process of JUICE, so that it can fulfil its mission before the damage becomes too severe and renders it unusable. In its work, Airbus has relied on Inventia Kinetics, which has provided the various mechanical ground support equipment for integration and testing.

Sener Aerospace has made the 10.6-metre-long deployable mast, from which several scientific instruments are to measure magnetic fields with extreme sensitivity, a reality. Made up of three sections that extend simultaneously thanks to three independent deployment mechanisms, in the words of Space director Diego Rodríguez, a veteran of the sector, it has been an "enormous technological challenge", to the point that its development "in colloquial terms, almost drove us crazy".

Not least because it is "about twice the size of any other similar pole we have ever built". It is anchored to a point on the satellite and when it is deployed "it has to stay totally rigid". Diego Rodríguez emphasises that verifying its operation has been "very difficult to test" and "we have had to use balloons to simulate its deployment in orbit".

Sener was also the design authority leading the international consortium of companies that developed the medium-gain antenna subsystem, a key part of the radio-science experiments to investigate the properties of Jupiter and its three moons. The company has also contributed its technology to the Janus medium-high resolution camera to observe Jupiter's atmosphere and the Gala laser altimeter to understand the tectonics of the ice enveloping the three moons.

Elecnor Deimos Space, the company headed by Ismael Lopez, has undertaken the planetary protection analysis of the mission, especially to prevent JUICE from colliding with Mars or with the moon Europa. It has also participated in developing computer tools for the autonomous navigation of the probe during its flyby of Europa and Ganymede.

Alter Technology has carried out the procurement and validation tests of 5,000 batches of components supplied by 80 European manufacturers for the ten instruments on board. GMV was responsible for the mission control system, which determines and controls the spacecraft's trajectory from the beginning to the end of its journey through the cosmos.

Airbus Crisa has fine-tuned the power electronics subsystem, the correct functioning of which determines the success of the mission. As the first European mission to travel the furthest distance from the Sun, optimising the electrical efficiency generated by its enormous 85 square metre solar panels is crucial. It is worth noting that the space agencies of the United States (NASA), Japan (JAXA) and Israel (ISA) are contributing equipment and instruments to JUICE.