After the ELT’s spectacular mirrors have collected, corrected and stabilised the light from astronomical objects, it is up to the instruments to analyse it in detail. The suite of instruments planned for the ELT includes cameras, to capture images, and spectrographs, which disperse light into its component colours, among other fantastic tools. Each of these will allow astronomers to observe and study the cosmos in a unique way.
Four of the instruments, the first generation, will start to operate at or shortly after ELT technical first light while an additional two (ANDES and MOSAIC) will start operations at a later stage. Throughout the telescope’s lifetime, other instruments will be installed on the telescope to study the Universe in ever more detail.
Selecting instruments for any telescope is a critical step in making sure that the astronomical community it serves can undertake the scientific projects for which the telescope was designed. ESO has been working with its community of astronomers and instrument builders to develop the sequence in which the instruments planned for the ELT will be built and delivered to the observatory. The result is an exciting programme of powerful facility instruments that can deliver the science cases for the ELT.
The first steps in developing the instrument plan were taken in 2007 when a plan for studying six instruments and two post-focal adaptive-optics-module concepts was presented to the ESO Council, ESO’s main governing body. Three additional instrument studies were chosen after an open call to the community for further concepts.
By early 2010 all of these ‘Phase A’ studies had successfully been completed in collaboration with institutes in the ESO community. Following recommendations by the ELT Science Working Group, the ELT Project Science Team, and ESO's Scientific Technical Committee, two first-light instruments were identified: a diffraction-limited near-infrared imager (ELT-CAM: MICADO) and a single-field near-infrared wide-band integral field spectrograph (ELT-IFU: HARMONI), including the adaptive optics systems required to deliver their science cases. The next three instruments, a mid-infrared imager and spectrometer (ELT-MDIR: METIS), a dispersion echelle spectrograph (ELT-ANDES: ANDES; formerly known as HIRES) and a multi-object spectrometer (ELT-MOS: MOSAIC), were considered of equal scientific importance.
On 10 July 2015, the ESO Council authorised the Director General to sign the contracts for the first set of instruments for the ELT, which includes MICADO, MAORY, a multi-conjugate adaptive optics unit that will feed MICADO (and possibly additional future instruments), HARMONI and METIS. On 8 December 2021, Council gave permission for the agreements for ANDES and MOSAIC to be signed. A schedule for the ELT instruments is provided in the table below.
One of the highest scientific priorities for the telescope is to characterise exoplanets and, specifically, to take images of Earth-like planets. Such a giant leap from the capabilities we have today requires significant research into new technologies over several years. Therefore, an ambitious and powerful planetary camera and spectrograph (ELT-PCS) is included in the instrumentation plan, and the research and development for specific components required to build it will start as soon as possible.