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June 25th 2019

Three Dutch PhD students, together with Leiden astronomer Frans Snik, have developed the technology in the past six months. "It's like an adventure novel," Snik reports from Canada. "The whole world is working on developing such technology for future space telescopes, and we are the first to test it in space with a group of young scientists."

The new technology was developed by Leiden University and space research institute SRON to eventually visually capture exoplanets. With this mission, scientists have now tested the technology for the first time at a high enough altitude such that the Earth’s atmosphere doesn’t form an obstacle. This makes the test comparable to a space mission.

HiCIBaS stands for High Contrast Imaging Balloon System and is built by Canadian students from the Université Laval in Quebec City. The instrument combines new technologies that filter out bright starlight, allowing astronomers to observe exoplanets right next to a star that is brighter thousands to billions of times. The Dutch team provided a so-called 'vector APP' coronagraph including corresponding algorithms. A conventional coronagraph simply uses a black disk to block starlight, but the extreme contrast of e.g. rocky exoplanets against their parent star requires more advanced methods.

For that reason, Snik's research group is developing coronographs that channel away the light from a star’s halo using liquid-crystal technology which was originally developed for tv screens. The group is already equipping most of the large telescopes on Earth with this technique, such as Magellan, Subaru, the LBT and the VLT. Now the team from Leiden University and SRON are the first to put a functioning version of this kind of advanced coronagraph on a space mission. HiCIBaS experienced technical problems during the flight when focusing on stars, but this was solved by using a laser. The test flight immediately showed that the coronagraph performs as designed in an extreme environment.

Future space telescopes
On Earth, enormous telescopes are currently being built with mirrors tens of meters in diameter. Such large telescopes have a high resolution and sensitivity, but turbulence in the Earth's atmosphere makes stars sparkle, thereby limiting the contrast for direct observations of exoplanets. In space it is difficult to achieve the same resolution and sensitivity, because large telescopes simply don’t fit into a rocket, but it is actually easier to get a higher contrast. Snik: "The very challenging goal is to eventually achieve a contrast of one in over a billion with future space missions. Our test is the first important step in that direction. We find out what exactly the practical difficulties are. Over the coming months we will analyze our data in detail. And when our instrument is brought back from the forest, 180 kilometers away where it landed, we can also inspect our optical components."

HiCIBaS is a step towards a space telescope to which both Leiden University and SRON can contribute with new technologies in the field of optics, highly sensitive detectors and complex control technology. Henk Hoevers (SRON): "In the future we want to study the atmosphere of an exoplanet that resembles the Earth. That is genuinely very difficult; every part of our instrument needs to be perfect. The combined technical knowledge that we now develop in Leiden and at SRON is essential for this."

More information
Website NWO Institute SRON