Oxford to build spectrograph for world’s largest optical telescope

The HARMONI project, which will provide £14.2 million of hardware and is led by Professor Niranjan Thatte from Oxford’s Department of Physics, will provide the world’s largest visible and infrared telescope with unprecedented physical insights about objects in the distant Universe.

Perched on top of Cerro Armazones in the Atacama Desert of northern Chile, the E-ELT will have a giant main mirror 39 metres in diameter. The telescope will enable scientists to peer further into the history of the Universe, studying distant, young galaxies in great detail with better sensitivity than ever before — helping improve our understanding of the Universe, the effects of dark matter and energy, and planets outside of our solar system.

When it is first used in 2024, the E-ELT will be equipped with three scientific instruments. One of these will be HARMONI, a spectrograph which splits the light from the object in the sky into its component wavelengths or colours. Astronomers can use these ‘spectra’ to determine far more than images alone ever can: they reveal the motion, temperature and chemical composition of structures imaged using the telescope.

In the past, most telescopes have used a technique known as slit spectroscopy to recover such data from the signals they receive, placing a narrow slit across an image of the night sky and determining its spectral content. But those techniques are slow and inefficient, and often provide limited insight. Instead, HARMONI uses a technique called Integral Field Spectroscopy to simultaneously obtain spectra over the entire field-of-view of the instrument.

HARMONI will slice the light entering the E-ELT into 152 separate slitlets, each of which will have its spectrum analysed for 214 points along its length. The result is a 214 x 152 grid of spectra, each containing 4,096 data points about the wavelength content of the signal at every spatial point. It will be versatile instrument, providing a range of scales, resolving powers and wavelength ranges — for instance, providing high resolution for bright objects and high sensitivity for dim, distant objects.

“HARMONI has been designed to be a workhorse instrument,” explains Professor Thatte. “It will be utilised by all the early science being carried out at the E-ELT. That’s why we designed it to be easy to calibrate and operate, providing the E-ELT with a ‘point and shoot’ spectroscopic capability.”

The device will be used across all of the E-ELTs experiments in its early years, from imaging planets to probing black holes. It will be used to directly observe planets and stars, providing early spectral analysis of exoplanets; to resolve individual stars, quantify the different types, their properties and their place in galaxy formation.

"We are privileged to be leading the design and construction of the first spectrograph for the E-ELT,” explains Professor Thatte. “It will revolutionise observational astronomy through the 2020s and beyond. By studying the light from galaxies, distant and nearby, in great detail, we hope to unravel the physical processes that have shaped the cosmos throughout its history.”

HARMONI will be built in a collaboration between the University of Oxford, the United Kingdom Astronomy Technology Centre and RAL Space in the UK. The project will take the equivalent of four hundred staff years of effort to complete. The project also includes contributions from Centre de Recherche Astrophysique de Lyon and Laboratoire d'Astrophysique de Marseille, both in France, along with Instituto de Astrofísica de Canarias and Centro de Astrobiologia, Instituto Nacional de Tecnica Aeroespacial, both in Spain.

Today’s agreement was signed by Professor Grahame Blair, Executive Director, Programmes, Science and Technology Facilities Council, on behalf of the consortium, and Professor Tim de Zeeuw, ESO Director General, at a ceremony at the University of Oxford.