How to build a space probe

Administration, design, mechanics, electronics, software development, science and project management: for the construction of space instruments, as with complex puzzles, a wide variety of components must be compiled into a whole. How does this work?

Ein Grund für eine kleine Feier: die erfolgreiche Fertigstellung des NIM-Instruments im August 2020. © Universität Bern
A reason for a small celebration: the successful completion of the NIM instrument in August 2020. © Universität Bern


On April 13, 2023, ESA's space probe Juice will begin its roughly eight-year journey to Jupiter. Its job is to search for life under the kilometer-thick ice layers of the giant planet's icy moons. Complex instruments were developed for this challenging task over many years – also at the University of Bern. Representing the approximately 40 employees of the local Institute of Physics who were involved in the construction of instruments for Juice, some of them share their insight into their work process.


The necessary papers are also needed for the journey into space

"If the package breaks, everything is broken," says Susanne Wüthrich, who has been a project assistant at the Department of Space Research and Planetology at the Physics Institute of the University of Bern for ten years and is responsible for transportation and administration. With each delivery of a flight instrument, she is thrilled: "If one little thing is wrong, you risk the instrument being stuck at customs for weeks."

With an international project like Juice, components or instruments are transported throughout Europe. Export declaration, special permit, tax exemption: Wüthrich is responsible for this and clarifies what is necessary to ensure smooth processing. Since regulations and requirements are ever changing, for example because of Brexit, she stays up to date. Every time an instrument arrives, she breathes a sigh of relief because the necessary components "can't be bought at the hardware store." She feels that working in an environment where "different teams share the same goal" is like winning the lottery.

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Knowing screws by their first name

Martina Föhn was responsible for the design of the Neutral and Ion Mass Spectrometer NIM, which will be used to study the atmosphere of the icy moons of Jupiter. NIM was developed and built at the Physics Institute of the University of Bern. Föhn has performed tests to ensure that the instrument will function reliably during its journey in space. Two identical copies of space instruments are built in each case: the flight model flies into space, while the reference model remains in the laboratory so that any tests can be performed during the mission. It took three months to build the flight model before it worked: "Each instrument has its own character. You get to know it very well, especially when it doesn't work so that over time you know certain screws by first name, so to speak."

For Harald Mischler, the acting workshop manager, there were also "quite a few headaches and many hours of disassembling, patching and re-testing". Föhn and his team built the reference model at the beginning of December 2020: "On December 21, I switched on the instrument for the first time, and it worked! That was the year's best Christmas present for me."

Symbolic of the close cooperation between those involved, Föhn recounts that during certain test phases she "practically had her own workstation" in the electronics technicians' office. The fact that certain work could only be performed in the laboratory meant that members of the NIM team received special permission to continue working at the Institute of Physics during the lockdown. Harald Mischler remembers those weeks, during which he worked with a small team in a completely empty institute: "Working nearly isolated from everyone else welded us together."


Die Menschen hinter Juice: Martina Föhn und Harald Mischler bauen das Massenspektrometer NIM in eine Testanlage ein. © Universität Bern
The people behind Juice: Martina Föhn and Harald Mischler install the NIM mass spectrometer in a test facility. © University of Bern

Electronics and software

Since 2014, Matthias Lüthi, who has been responsible for the concept and construction of NIM’s control electronics, which is used to operate the instrument, is fascinated by the "interplay of extremely small currents, high voltages, complicated mechanics and complex software." He works with Severin Oeschger, who is responsible for the design and construction of the electrical high voltage: "Before I started working on the Juice project, high voltage meant that I simply needed a lot of space. Now we have 14 different high voltages built into an area of 13 x 13 cm and 4 cm high."

The decisive factor in hiring Oeschger, the electronics engineer on the NIM team, was not only his skills but also the experience he gained from the CHEOPS project. He sees his manual skills, which he owes to his apprenticeship and technical university studies, as an ideal complement to the scientific environment: "It enables me to ultimately develop a real functioning measuring device from the rather theoretical construct of the researchers. This gives them the opportunity to get closer to their questions and goals – even in very harsh conditions."

Oeschger agrees with Lüthi when he says: “A project like this requires a lot of perseverance. In some cases, unconventional solutions are also possible.” Michael Althaus had to resort to such solutions more than once. He developed the software for NIM, always keeping in mind that "it's not enough to focus only on your own instrument." Instead, the software engineer says, "for a lot of things, you also have to include the entire complex system, which is Juice, but also the actual commanding by Mission Control at ESOC in Darmstadt." After the launch on April 13 2023 there is still «a bigger chunk of work for him with the commissioning of the instrument».

Mitarbeitende der Weltraumforschung und Planetologie (Thierry de Roche, Michael Gerber, Matthias Lüthi) in einem Reinraum mit dem Massenspektrometer NIM, das an der Universität Bern gebaut wurde. © Universität Bern, Bild: Thierry de Roche
Employees of Space Research and Planetology (Thierry de Roche, Michael Gerber, Matthias Lüthi) in a clean room with the NIM mass spectrometer built at the University of Bern. © University of Bern, Image: Thierry de Roche

Practically starting over from scratch

After 17 years in space instrument development, Daniele Piazza, head of mechanical design, is also facing new challenges in this project. It is particularly the high-energy radiation prevailing in the Jupiter system that causes the greatest problems for Juice. For example, this can impair the function and reliability of the electronics, which must therefore be housed in a solid enclosure. Due to its high density, tungsten represented the most efficient solution for the implementation of the housing. This makes it even more important to shield the detectors, whose signals would otherwise be disrupted by the radiation. To protect the detector of the NIM spectrometer, which is only one centimeter in size, one kilogram of tungsten was needed – a lot of weight for an instrument that will then fly into space!

The unusually high mass of the hardware led Piazza and his team, in collaboration with the company that built the spacecraft, to "revolutionize the entire architecture – even though the design of the instrument was already advanced," he says proudly. The instrument was not integrated as usual onto its own structure, which is then screwed onto the space probe. Piazza tells: ”The company provided part of the satellite and we integrated our sensors and electronics box on this panel. That was a huge improvement, because a lot of mass could be saved. ” The fact that this more complex but more efficient solution was only tackled late in the development process is due to the complex procedure involved in the construction of research space probes. Many partners are involved and there are accordingly many interfaces. When the design team at the University of Bern began developing the instrument, it was not yet clear which company would build the space probe. It wasn't until the company was selected that work "practically had to start from scratch," Piazza said.

Das Massenspektrometer NIM beim Zusammenbau am Physikalischen Institut der Universität Bern. © Universität Bern, Bild: Martina Föhn
The NIM mass spectrometer during assembly at the Physics Institute of the University of Bern. © University of Bern, Image: Martina Föhn

Getting a little closer to Jupiter

"Through this project, Jupiter, despite its vast distance, has come a little closer to me: When the sky is clear, I'll definitely find myself looking for Jupiter again and again in the future," says Mikko Kotiranta, project manager at the Institute of Applied Physics (IAP) at the University of Bern for the Submillimeter Wave Instrument SWI. The SWI is equipped with a telescope that cannot measure visible light, but can measure thermal radiation in the submillimeter wavelength range. For example, this is important, to measure the temperature distribution in Jupiter's atmosphere and the surface properties of its icy moons. A team of four designed the optics for this at the University of Bern. Their role was also to determine with the utmost precision how wide the telescope beam is and where it is pointing – knowing this is imperative for reliable measurements. A tricky task with an invisible beam. The scientists solved this task using complex simulations and a new type of test bench developed for the SWI.

Karl Jacob, now Co-Investigator for the SWI and formerly a PhD student at the University of Bern, had the opportunity to work on the flight model for six months at the Max Planck Institute for Solar System Research (MPS) in Göttingen. He remembers how, "after an intense testing phase with enormous time pressure and unexpected incidents, he was able to toast a beer with the other team members."

Juice is expected to reach its goal in 2031. It is quite possible that the insights gained then will be groundbreaking – and the University of Bern will be significantly involved. "Hopefully, this will not only bring Jupiter closer to me, but to all of us," says Kotiranta.

Karl Jacob mit der SWI Empfängereinheit nach erfolgreichen Kalibrationstests im Reinraum am MPS in Göttingen. © Karl Jacob
Karl Jacob with the SWI receiver unit after successful calibration tests in the clean room at MPS in Göttingen. © Karl Jacob


The people behind Juice

This article is part of a series introducing the people at the University of Bern who are involved in the Juice space mission. In the first article "From Vision to Mission," researchers at the University of Bern who are significantly involved in the implementation of Juice were portrayed. Read the third article on the three instruments with Bernese participation on 22 March 2023.

To the previous article:

"From vision to mission"

Juice exhibition

Starting in April 2023, an almost three-meter-long model (1:10) of the Juice space probe and instruments will be on display at the Physics Institute of the University of Bern (Sidlerstrasse 5, first floor). The content of the exhibition may vary because the instruments are in part being used for tests! In the further project phases, certain instruments that have remained on Earth will be used to receive and analyze data and to reconstruct the measurements made in space in the laboratory to verify the results.

Juice Launch Event

With live stream from Kourou and space talks

Thursday, April 13, 1:00 to 4:00 p.m.

University of Bern, “Exakte Wissenschaften” building, Sidlerstrasse 5, 3012 Bern, lecture hall 099

The event will be held in German and French.


The Neutral and Ion Mass Spectrometer (NIM) has been developed and built at the Physics Institute of the University of Bern under the direction of Peter Wurz. NIM is part of the Particle Environment Package (PEP), which consists of six different spectrometers. The NIM mass spectrometer will study the chemical and isotopic composition and distribution of particles in the atmospheres of Jupiter’s icy moons, as well as the physical parameters of the moons’ atmospheres.

The Institute of Applied Physicsldeveloped the optics and calibration unit for the Sub-millimeter Wave Instrument (SWI) under the direction of Axel Murk. In the fall of 2020, the optics for the SWI were integrated and tested at the Max Planck Institute for Solar System Research. The SWI will measure Jupiter’s stratosphere and the atmospheres and surfaces of Jupiter’s icy moons. Instead of visible light, the instrument will measure thermal radiation from Jupiter’s stratosphere in sub-millimeter wavelengths to determine temperature distribution, composition and winds in the atmosphere. The atmospheres as well as the surface properties of the moons will also be studied.
Also on board  will be the GALA Laser Altimeter, for which the Range Finder Module was developed for at the Physics Institute under the direction of Nicolas Thomas. GALA will study the topography of Ganymede.

More information about the JUICE Mission:

Support of the SERI / Swiss Space Office

The Swiss Confederation participates in the Juice Mission within the PRODEX programme (PROgramme de Développement d'EXpériences scientifiques) of the European Space Agency. Through this programme, national contributions for science missions can be developed and built by project teams from research and industry. This transfer of knowledge and technology between science and industry ultimately also gives Switzerland a structural competitive advantage as a business location – and enables technologies, processes and products to flow into other markets and thus generate added value for our economy.