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ING press release
31 October, 2023

Inauguration of WEAVE

The WEAVE spectrograph, a powerful, next-generation multi-fibre spectrograph installed on the William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands), was inaugurated on October 30th, 2023.

The inauguration ceremony brought to La Palma the leaders of the science funding agencies from the partner countries of the Isaac Newton Group of Telescopes (ING), as well as a strong representation from the 500 members of the science teams and the organisations involved in the design and construction of WEAVE, making it the largest ever gathering of people inside the dome of the WHT.

Group photograph of attendees. Credit: Javier Méndez. Large format: PNG.

The inauguration ceremony was full of excitement and celebration. The WEAVE project was launched more than 10 years ago thanks to the push of a great team of astronomers who saw in wide-field spectroscopy using optical fibres the potential to exploit large data sets, such as those provided by the European Space Agency's (ESA) Gaia satellite, and a new role for the William Herschel Telescope, now refurbished and equipped with one of the largest astronomical lenses ever built.

After intense years of design and construction of its multiple elements in countries on four continents, WEAVE was finally installed at the WHT in May 2022, and it obtained its first scientific data in December of the same year. During 2023, several of its observation modes have been fine-tuned, and data have been obtained to verify its scientific capabilities.

The inauguration of WEAVE marks the beginning of its regular scientific exploitation, and more specifically, the kick-off of the WEAVE Survey and open-time programmes using its large integral-field unit (LIFU). Science programmes using the multi-object spectroscopy (MOS) mode are due to start in 2024, followed by observations with WEAVE's third observing mode using small integral-field units (mIFU).

The new prime-focus corrector of the William Herschel Telescope, now equipped with one of the largest astronomical lenses ever built. Credit: Kane Sjoberg. Large format: PNG.

WEAVE, the instrument

WEAVE is a multi-mode, multi-fibre spectrograph which uses optical fibres to gather light from celestial sources and transmit it to a spectrograph. The WEAVE two-arm spectrograph separates the light into its different wavelengths, or colours, and records them on large-format CCD detectors. The raw data are transferred over the internet to computers in Cambridge and Tenerife, and the science-ready products are stored in an archive on La Palma for scientific exploitation. The resulting spectra contain the fingerprints of the physical and chemical properties of stars, galaxies, quasars and interstellar and intergalactic gas, which astronomers use to test their theories about the Universe, and which also enable astronomers to measure velocities along the line of sight through the Doppler effect.

One of WEAVE's unique features among multi-object spectrographs is its superb sharpness when splitting the incoming light into its component wavelengths, also known as spectral resolving power, for as many as 960 celestial sources simultaneously. While the spectral resolving power of WEAVE in low-resolution mode is comparable to that of other current multi-object spectrographs, its resolving power in high-resolution mode is five to ten times greater than that of other multi-object facilities in the northern hemisphere. This high resolving power means more accurate velocity measurements (as good as 1 km/s) and much more accurate chemical-abundance measurements than can be obtained with other northern-hemisphere MOS facilities.

WEAVE's versatility is another of its strengths. While the LIFU mode hosts 547 fibres closely-packed to image extended areas of the sky, in the MOS mode two robots separately position up to 960 individual fibres to gather light from as many stars, galaxies or quasars. In the mIFU mode, the fibres are organised into 20 units, each comprising 37 fibres that are used to study small extended targets such as nebulae and distant galaxies.

A fully-configured WEAVE field, with 700 of 960 fibres placed by two robots over a 2-degree field of view. Credit: Gavin Dalton. Large format: JPG.

The WEAVE science

In the coming years the ING will assign 70% of the time available on the WHT to the WEAVE Survey, a set of eight major surveys selected out of those proposed by the astronomical communities of the partner countries. The WEAVE Survey will provide data that will help answer questions such as how our Galaxy formed and the stars within it evolved, how other galaxies were assembled, and what dark matter and dark energy are.

Together, these surveys will require spectra of several million stars and galaxies, a goal now obtainable thanks to WEAVE's ability to observe almost 1000 targets at a time (MOS mode). In synergy with ESA’s Gaia satellite, the MOS mode of WEAVE will be used to obtain spectra of stars in the disc and the halo of our host galaxy, enabling Milky Way archaeology. Galaxies near and far, some detected by the LOFAR radio telescope, will be studied to learn the history of their growth. And quasars will be used as beacons to map the spatial distribution and interaction of gas and galaxies when the Universe was only around 20% of its current age.

The remaining 30% of the time available is reserved for projects selected competitively from those proposed by astronomers in the ING partner countries (UK, Spain, Netherlands). The WEAVE Open-Time Programme, as it is called, will leverage WEAVE’s versatility to provide fast responses to immediate questions.

There are also channels for programmes that jointly exploit WEAVE and the diverse capabilities of the telescopes in the Canarian Observatories such as the 10.4-metre Gran Telescopio Canarias. These programmes foster scientific collaboration between astronomers working in all countries that operate telescopes at the Canarian Observatories.

A JWST image with the WEAVE LIFU pointing at Stephan's Quintet for the first-light observation. The LIFU gathers light from 547 points on the sky for analysis by the WEAVE spectrograph (each circle indicates an optical fibre 2.6 arcseconds in diameter). Credits: NASA, ESA, CSA, STScI (background image); This composite has made use of "Aladin sky atlas" developed at CDS, Strasbourg Observatory, France. Large format: PNG.

WEAVE funding and construction

ING initiated plans to build WEAVE after extensive consultation with the ING user community about what was needed for the future. There was a broad consensus that a world-class wide-field multi-object spectrograph was required to exploit from the ground the huge surveys being undertaken by powerful telescopes such as as ESA's Gaia, thereby helping to address the main astrophysical challenges foreseen for the next decade.

In 2016, the multi-lateral agreement to design and build WEAVE was signed by the countries of the ING partnership (the UK, Spain and the Netherlands), joined by France and Italy, with each country contributing major components as listed below, and with the ING providing auxiliary systems and overall project management.

The instrument construction team is led by Gavin Dalton from Oxford University as Principal Investigator, Scott Trager from Groningen University as Project Scientist, Don Abrams from ING as Project Manager, and Chris Benn from ING as Instrument Scientist. The main components of WEAVE are:

  • Fibre–positioner, developed by the University of Oxford and RAL Space in the UK, with support from the Instituto de Astrofísica de Canarias (IAC) in Spain.
  • Prime-focus system, designed by ING, IAC and SENER, provided by the IAC and manufactured by SENER. Support from Konkoly Observatory (HU). Lenses were polished by KiwiStar in New Zealand, funded from STFC, NOVA, INAF, IAC and ING, and mounted at SENER Aeroespacial (ES) by SENER and ING.
  • Spectrograph, built by NOVA in the Netherlands with optical design by RAL Space in the UK, optics manufactured at INAOE (MX) and with support from INAF (IT) and the IAC.
  • Field Rotator, provided by IAC and manufactured by IDOM (ES). Optical fibres, provided by the Observatoire de Paris in France, manufactured in France, Canada and USA.
  • LIFU, built by NOVA (NL).
  • CCD detectors system, provided by Liverpool John Moores University in the UK. Data processing, analysis and archiving led by University of Cambridge (UK), IAC (ES) and FGG-INAF (IT) respectively.
  • Observation control system, built by the ING.

WEAVE's construction has been funded by the Science and Technology Facilities Council (STFC, UK), the Netherlands Research School for Astronomy (NOVA, NL), the Dutch Research Council (NWO, NL), the Isaac Newton Group of Telescopes (ING, UK/NL/ES), the Instituto de Astrofísica de Canarias (IAC, ES), the Ministry of Economy and Competitiveness (MINECO, ES), the Ministry of Science and Innovation (MCI, ES), the European Regional Development Fund (ERDF), the National Institute for Astrophysics (INAF, IT), the French National Centre for Scientific Research (CNRS, FR), Paris Observatory – University of Paris Science and Letters (FR), Besançon Observatory (FR), Region île de France (FR), Region Franche-Comté (FR), Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE, MX), National Council for Science and Technology (CONACYT, MX), Lund Observatory (SE), Uppsala University (SE), the Leibniz Institute for Astrophysics (AIP, DE), Max-Planck Institute for Astronomy (MPIA, DE), University of Pennsylvania (US), and Konkoly Observatory (HU).

About the William Herschel Telescope

The William Herschel Telescope (WHT) is operated on the island of La Palma by the Isaac Newton Group of Telescopes (ING) in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC). The ING is funded by the Science and Technology Facilities Council (STFC-UKRI) of the United Kingdom, the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands, and the IAC in Spain. IAC's contribution to ING is funded by the Spanish Ministry of Science, Innovation and Universities.

More information

WEAVE Inauguration Event web pages.

The WEAVE Survey

The WEAVE Project

"WEAVE First Light", ING Press Release, 12 December 2022.

Shoko Jin et al., 2023 "The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation", MNRAS, stad557. Paper.


Javier Méndez
ING PR Officer

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Last modified: 13 November 2023