These days, three men in Bern are looking eagerly towards Kourou in French Guiana: this is where the European spaceport is located, from where the European Space Agency's (ESA) space probe Juice (Jupiter ICy moons Explorer) will begin its journey to Jupiter on board an ARIANE 5 rocket on Thursday, 13 April 2023 at 2:15 pm. On board are ten space instruments that will study the largest planet in our solar system and three of its moons after a journey of about eight years.

The three men are Peter Wurz, Nicolas Thomas and Axel Murk, who are involved in instruments that will soon fly to Jupiter with Juice. The University of Bern is contributing the mass spectrometer NIM to the Juice mission and is involved in two other instruments: The Submillimeter Wave Instrument SWI and the Laser Altimeter GALA.

Of money and cosmic radiation

In March 2007, ESA had issued a call for mission proposals for its space mission program "Cosmic Vision 2015-2025". One of the proposals selected for further consideration was LAPLACE, a mission to Jupiter. In cooperation with NASA, LAPLACE was first developed into a mission concept known as EJSM (Europa-Jupiter System Mission) and, building on this, was finally elaborated by ESA into the Juice space mission.

In 2009, Nicolas Thomas was chairman of ESA's "Solar System Working Group" and was thus involved in the mission concept to Jupiter from an early stage. Today, Thomas is the director of the National Centre of Competence in Research NCCR PlanetS, which the University of Bern leads together with the University of Geneva. And under his leadership at the University of Bern, the so-called 'Range Finder Module' for the GALA laser altimeter on board Juice was developed, which will investigate the surface topography and the inner structure of Jupiter's moon Ganymede.

Thomas explains: "The outer solar system contains a large amount of information about the origin and evolution of our solar system as a whole. This is the main reason why both ESA and NASA are currently focusing on objects like Jupiter and its moons." According to the researcher, the investigation of water and water ice on icy moons such as Europa and Ganymede will also give us a better understanding of the role of water in places where life could have emerged and existed in the longer term – in our solar system and beyond.

One of the biggest obstacles that had to be overcome was the financing of GALA. "After more than a year, however, our German project partner finally managed to secure the funding," says Thomas. In his view, the biggest challenge on the journey to Jupiter is "quite clearly cosmic radiation! Electronic components don't like being exposed to radiation in space."

Of low temperatures and many measuring cycles

Axel Murk, who today heads the Department of Microwave Physics at the Institute of Applied Physics at the University of Bern, has also been involved in the Juice mission concept since 2009. Under his leadership, the optics and calibration unit for the Submillimetre Wave Instrument (SWI) were developed. "The SWI will measure the thermal radiation from Jupiter's atmosphere, with which the chemical composition, the temperature distribution and wind speeds in Jupiter's atmosphere can be determined", as Murk explains.

"Originally, NASA was supposed to participate in the Submillimetre Wave Instrument," Murk says. However, NASA cut the funds earmarked for it and the instrument had to be developed without the US partners.

However, funding issues were not the only challenge for Murk either. "Our instrument contains several moving components that still have to work precisely at the low temperatures in the Jupiter system and during many measurement cycles. This is essential for the correct viewing direction and calibration of the instrument. The lifetime of these mechanisms is a big challenge under the environmental conditions of the mission," Murk explains.

Of complex requirements and risky flybys of planets

Also involved since the early days of the Jupiter mission's design phase is Peter Wurz, current Director of the Institute of Physics. He is the Co-Principal Investigator of the PEP experiment, which consists of six mass spectrometers, which will precisely measure Jupiter's moons. Wurz also led the development of the NIM instrument, which is part of PEP. NIM was not only developed at the University of Bern, but was also built and tested here.

Asked about the biggest challenge in the project, Wurz says: "The complexity of NIM was challenging: on the one hand, the instrument has to be small and light and consume little power, but on the other hand, it has to deliver high performance in order to achieve the scientific goals and survive the high radiation environment in Jupiter's orbit. Many things had to be developed and tested specifically for this mission.”

International cooperation is also complex: because space instruments are technologically advanced, often not all the expertise is available at a single institution. Wurz says: "You form international teams to which each partner institution contributes its respective expertise and in which you can share the costs of developing such an instrument."