More than 400 years after Galileo discovered the four great satellites of Jupiter –Europa, Ganymede, Callisto and Io–, on April 13, at 2:15 pm (Spanish peninsular time), the European Space Agency (ESA) plans to launch the Jupiter Ice Moons Explorer (Juice) to investigate the first three.
The details were explained this week by Nicolás Altobelli, responsible for the development of the scientific activities of this mission, and by the responsible for the scientific operations, Claire Vallat, during a press conference at the European Space Astronomy Center (ESAC) operated by ESA. in Villanueva de la Cañada (Madrid).
The Juice mission leaves on April 13 to study, from 2031, three icy moons of Jupiter: Europa, Callisto and, above all, Ganymede.
Juice’s objective is to characterize Europa, Callisto and Ganymede, of near planetary size, and the potentially habitable environments that could have developed in their interior, taking into account the evidence that points to the existence of large masses of liquid water under its surface. of ice.
“We know of exoplanets like Jupiter orbiting stars, but this is an astrophysics laboratory in our neighborhood, very close to us, an archetype of gas giant planet”, says Altobelli, who recalled that water can remain liquid in the subsoil of these moons. , beyond the zone traditionally considered habitable (neither too far nor too close to a star).
“We have to understand the physics that governs the evolution of these icy aquatic worlds – he emphasizes –, and we have to go there because that way we can study what happens in similar places in the galaxy”.
To fulfill its objectives, Juice has 10 instruments, such as spectrographs in all wavelengths; a radar and laser altimeter to study the surface and subsurface of the moons; magnetometers to measure its gravity field and various sensors to detect, for example, charged particles (plasma) in the environment.
“The total mass of this ‘beast’ is six tons and we have 3,500 kilos of fuel on board,” says Altobelli, “although the ship is also powered by 85 square meters of solar panels”. As for communications with Earth, they are established with a 2.5 m high-gain antenna and a medium-gain one.
spanish contribution
The main contractor for this mission, which has a total budget of €1.6 billion, is the company Airbus. “Spain’s contribution is quite significant”, highlights Altobelli, as it supplies ten scientists and several instruments (JANUS camera subsystems, GALA laser altimeter, MGA magnetometer and internal structure of the satellite).
In addition to CSIC and INTA, several Spanish companies in the aerospace sector are participating: Sener, Alter, Airbus-Crisa and Airbus Defense/space, which developed 500 kg of internal structure.
Spain’s contribution is quite significant, as ten scientists and several national companies participate in various instruments (camera subsystems, laser altimeter and magnetometer) and the internal structure of the satellite
Nicolás Altobelli (ESA-ESAC)
In this mission by ESA and its member countries, NASA also contributes (with the ultraviolet spectrograph and plasma sensors), the Japanese space agency JAXA and Israel, contributing with various subsystems.
The Juice satellite has already been transferred from the Airbus facilities in Toulouse (France) to the Kourou spaceport in French Guiana. In early April, it will be placed on the Ariane 5 rocket and then moved to the launch pad. “This will be a historic milestone because it will be the last of an ESA science mission with an Ariane 5,” according to Altobelli.
The spacecraft’s signals will reach the deep space network of ESA and perhaps NASA (both have antennas in Spain, in the town of Cebreros in Ávila and Robledo de Chavela in Madrid, respectively). Operations will be managed from the European Space Operations Center (ESOC) in Germany, but project coordination and scientific planning will be done from ESAC, from where mission science data will also be distributed worldwide.
A long journey of more than eight years
For her part, Claire Vallat detailed the probe’s long journey. Although the launch window has been open for about a month, those responsible for the mission are confident that it will be April 13th as scheduled, in order to perform all the predicted gravity assists and save fuel.
After the 30-minute launch phase is over, the satellite’s appendages and its 10 solar panels begin to be deployed to provide power. In the following days, until April 17, the magnetometer arm that will measure the magnetic field around the probe and the various antennas is also open.
“Then the cruise phase begins, which will take approximately 8 years, during which time the gravitational assistance of the Earth-Moon system will be assisted for the first time, and which will take place next year”, explained Vallat. Then will come gravitational assistance from Venus and two more from Earth in 2026 and 2029 to put the probe on a trajectory to Jupiter, where it will arrive in 2031.”
Juice mission stages. / WHAT
Six months before arriving at Jupiter, the nominal phase, the scientific phase of the mission, begins. The probe will approach the gas giant system and its Galilean moons, where it will operate for three and a half years.
“During this period, we will make a few flybys: two over Europa (July 2032) at an altitude of 400 kilometers, 21 over Callisto (until August 2033) and then the transfer to Ganymede, where the spacecraft will make 12 flybys. into orbit in December 2034, descending from 5,000 to 500 km in altitude”, explains the mission scientist.
Juice will be the first probe to orbit around a moon other than our own: Ganymede
Claire Vallat (ESA-ESAC)
Vallat points out that “Juice will be the first probe to be placed in orbit around a moon other than our own”. The mission will end with the spacecraft’s impact on the surface of Ganymede in September 2035. Any risk of possible contamination of the lower ocean is ruled out, as the icy crust is more than 100 km thick.
Altobelli points out that one of the objectives is to make a ‘tomography’ of this satellite: “It is the first time that we are going to do it, and it cannot be done with a few flybys, it has to stay in orbit at different altitudes to study the environment well. magnetic field allow us to study how the inner layers contribute to what we measure.”
Overcoming operational and human challenges
Vallat also recalled the operational challenges the mission will face: high levels of radiation from which electronic equipment will have to be protected, low electrical energy (because it is too far from the sun) and thermal challenges.
The mission, in which more than 2,100 people participate, will face human and operational challenges, such as withstanding thermal differences of +/- 200 °C
“The probe will pass very close to a hot environment when it passes by Venus, with temperatures above 200 degrees Celsius –he gave an example–, but when we are in the shadow of Jupiter, temperatures can drop to less than 200 degrees Celsius. degrees, so it has to withstand these big temperature differences.”
“And above all – he concludes – there are many human challenges, because it is a mission with more than 2,100 people working in different parts of the globe. We have to be able to organize a scientific observation plan that allows us to answer humanity’s questions about the icy moons and the Jovian system as a whole.”
The moon Ganymede orbiting Jupiter. / Hubble (ESA/NASA)