Another goodbye to Herschel

The Herschel telescope had let them down, Rens Waters told the assembled technicians and astronomers at the University of Groningen Academy Building on 18 April. They had come together to celebrate the end of a very successful mission, but Herschel stubbornly refused to stop. A few weeks ago when they were planning the party no one thought the telescope would still be active by then. But it was.

‘Herschel let us down, but in a good way!’ Waters told his audience, adding that he had just filed another observation proposal himself. ‘We analysed some data and found it very interesting. But we needed more. The proposal was approved this morning, but I have to wait my turn, so I hope Herschel will keep going for another two weeks.’

Waters, an astronomer at the University of Amsterdam, is also director of SRON, the Netherlands Institute for Space Research, which built the HIFI spectrometer, one of three instruments on board Herschel. The party was to celebrate this huge effort that took almost twenty years from idea to launch.

Staff from SRON and the University of Groningen’s Kapteyn Institute for Astronomy enjoyed a buffet meal before listening to the personal experiences of three members of the Heterodyne Instrument for the Far-Infrared (HIFI) team. The common theme in all these stories was the team effort. Half the parts used for HIFI simply didn’t exist when the project started. The team had to invent, design and test everything.

Pieter Dieleman recounted how during the final assembly of the HIFI spectrometer the team averaged only five hours sleep per night in order to meet the delivery deadline. After delivery, HIFI was mounted on the telescope and the entire satellite was tested for the first time at operating temperatures in a gigantic cooler at the European Space Research and Technology Centre (ESTEC) in Noordwijk.

When it was HIFI’s turn, a small team switched it on, and experienced all sorts of system malfunctions. Having heard about the problems, reinforcements soon arrived without the core team even needing to send out a call for help. Some came to Noordwijk, whereas others logged on from their own computers.

The team doubled and then tripled in size and spent a gruelling fortnight troubleshooting. Everyone pitched in. They survived on pizza, and even slept at their desks. In the end, they managed to get everything working, and working brilliantly at that.

At the party they remembered the stress of the launch, but only touched on the time that HIFI was damaged by an incoming high-energy cosmic particle. It took several months to understand what had happened, and how to deal with such an event. Again, everyone buckled down, and they found a way to get HIFI up and running, despite a much heavier than expected onslaught of high-energy particles.

Above all, there was the excitement about the scientific data. HIFI provided the first glimpse of wavelengths that had never been observed before. Waters recalled the excitement he felt as a scientist. ‘When I got my first data, I could look at a spectrum that no one on this planet had ever seen. This was truly amazing.’

After the team had finished reminiscing, it was the turn of the Grieg Pianoduo to perform music inspired by galaxies and stars by the Estonian composer Urmas Sisask. University of Groningen astronomer Peter Barthel provided accompaniment in the form of astronomical images. He regularly performs with the duo in concert halls all over the country.

After the music, a dessert was waiting for the roughly 80 attendees. The evening was a fitting homage to a remarkable accomplishment, and it served to whet the appetite for new projects. SRON and the Kapteyn Institute are both looking ahead to a new instrument, Safari, which will be HIFI’s successor.

Of course, HIFI is still running. ‘But the money will run out in August, so we will have to end observations then’, team member Frank Helmich joked. Because no one really believes it will last that long. It can’t. Can it? ‘It can’t, but no one really dares to make predictions anymore.’

The next farewell to Herschel party is planned on 8 May, at the Royal Netherlands Academy of Arts and Sciences.

Pictures: Willem Jan Vreeling, SRON