Far-away galaxies: Modern telescopes rely on Kaiser’s optical expertise

Toward the Big Bang

While advanced analytics is strengthening the Endress+Hauser core business, it’s also claiming success in niche markets: optical elements from Kaiser are providing deep insights into the universe.

Billions of light years away: With optical elements from Kaiser, the Very Large Telescope located in Chile (our image shows a 360-degree-panorama) is the world’s most powerful observation facility for viewing the visible light spectrum.

The view of the galaxy on a clear, starlit night was probably just as fascinating for our ancestors as it is for us today. Astronomy is not only one of the oldest scientific disciplines, but also one of the most dynamic and still a driver of technological progress.

When it comes to precision, the famous deep field Hubble telescope images were long considered the measure of all things. Astronomers at the European Southern Observatory (ESO) have now managed to shed an even deeper light on the universe. In a small patch of the sky, more than 20 very faint objects not previously recorded by the Hubble telescope were revealed, including galaxies more than ten billion light years away. Since that is also the time it takes the light to to reach us, from the perspective of the Big Bang these galaxies are still in their infancy. They help us draw conclusions about the development of own galaxy, the Milky Way.

Optical time travel While the Hubble team had to analyze each galaxy individually, a new technology makes it possible to immediately determine the distance (and with closer objects even the rotation) of 189 galaxies at the same time. Scientists owe this unsurpassed capability to the Multi Unit Spectroscopic Explorer MUSE, installed in late 2014 at the Very Large Telescope situated in the Chilean Atacama Desert, the flagship facility for European ground-based astronomy. The seven-ton MUSE instrument, financed by 16 European countries, is every astronomer’s dream. “It was like fishing in deep water. Each new catch generated great excitement and prompted discussions about the species we were finding,” explains Roland Bacon from the Centre de Recherche Astrophysique de Lyon and head of the MUSE research project.

Superior sensitivity At the heart of MUSE are Volume Phase Holographic Gratings (VPHG) from Kaiser Optical Systems. Although this is a tried and tested technology in the petrochemical and life sciences industries, the gratings had not been used in the field of astronomy until a US astronomer based in Arizona read about the sensors in an industry article in 1993. Like all spectrographs, VPHGs disperse the light into its component wavelengths so that the properties of the material can be analyzed, similar to a DNA analysis. Given that VPH technology has the potential to offer more light sensitivity than conventional gratings – why not exploit this advantage at an observatory as well?

“We sat at the table with the customer and two years later we were able to equip the first telescope with an advanced optical element,” explains James Arns, Senior Optical Systems Engineer at Kaiser. The superior throughput of the VPH diffraction grating was confirmed as part of a national research project. After a renowned ESO scientist came to the same conclusion, the heavens were finally open for the technology. To date, more than 20 telescopes worldwide have been equipped with different types of VPH elements.

“The diffraction gratings from Kaiser are the key to high performance in MUSE.”

Ronald Bacon, head of the MUSE research project

Billions of light years away: With optical elements from Kaiser, the Very Large Telescope located in Chile (our image shows a 360-degree-panorama) is the world’s most powerful observation facility for viewing the visible light spectrum.

“Since every astronomical spectrograph is a unique instrument, each order presented a new challenge,” says James Arns. “We were able to further optimize our technology and as a result become the preferred supplier for ESO, based on many years of experience.”

Highly complex  Not only the telescope but also the developers were pushing ahead into a new dimension. The trick was integrating 24 individual spectrographs, each with its own grating, that work in unison to collect thousands of spectra of stars and galaxies simultaneously, thus making it possible to create a quasi-three-dimensional image. “The MUSE project challenged us to build multiple VPH gratings to a high degree of uniformity. In order for all of the data to have maximum value, each spectrograph has to operate as a twin or clone of all the others that make up the instrument,” explains James Arns. Kaiser eventually produced additional gratings allowing MUSE assembly engineers to selectively balance the performance of each spectrograph to that of the overall instrument.

“Through close and honest communication with the customer, we developed a working relationship based on mutual trust. That resulted in a revised specification which aligned scientific wishes with technical feasibility,” says James Arns in summary. Since then, the Very Large Telescope has peered deep into the night sky to collect a maximum of information from rare light that has travelled billions of years. “VPH diffraction gratings are the key to high performance in MUSE,” says Roland Bacon. “I am grateful for the excellent work delivered by Kaiser.” An eagle’s eye After ten years of development, the Multi Unit Spectroscopic Explorer MUSE was mounted on Telescope 4 of the Very Large Telescope in 2014. The telescope relies on 24 spectrographs incorporating VPH gratings from Kaiser Optical Systems. For every part of the view, a spectrum reveals the intensity of the light’s different component colors at that point, about 90,000 in all. These can reveal the distance, composition and internal motions of hundreds of different galaxies, or very distant stars in the Milky Way. Deformable mirrors correct in real time the distortion caused by atmospheric turbulence (‘adaptive optics’).