Last updated 20th February 2026

This page provides an overview of the instrumentation available at the WHT and INT in 2026.

WEAVE on the WHT

1. WEAVE. Regular science observations with the LIFU (integral-field) mode of the WEAVE multi-fibre spectrograph started in October 2023. After a standdown (Sep 2024 - Jun 2025) to allow the spectrograph optics to be re-aligned by a team from NOVA, LIFU science observing, and commissioning of the MOS mode, resumed.

   MOS science-verification observations began in October 2025. In parallel, there is ongoing work to improve the fibre-positioning, to make more efficient use of the night. The MOS science surveys are expected to begin ~ April 2026.

   The mIFU (mini-IFUs) mode of WEAVE is currently being commissioned.

   The 2026B call for proposals invites observers to submit requests for open-time observations with LIFU (including limited target-of-opportunity observations), MOS and mIFU (the latter in shared-risk mode).

2. Time distribution and instrumentation in the WEAVE surveys era. With the start of WEAVE science operations, the WHT changes from being a classical observing telescope to a queue-driven operation, with a 70% / 30% split between surveys and open time, after provision is made for 5% ITP (international time).

   Given the complexity of mounting and dismounting WEAVE, other instrumentation (e.g. ISIS, ACAM) are not currently being offered. Observers can safely assume that WEAVE will be continuously mounted on the WHT for at least the coming 2 years. Discussion of some of the issues involved can be found in the 2019 WHT telescope time document.

3. Pipeline-processed WEAVE data. Preliminary data products for nearly all of the WEAVE science data taken to date are available to the proposing teams at the WEAVE Operational Repository in Cambridge.

   We remind users that the data provided in the WEAVE Operational Repository can be used for monitoring progress and for quality control, but may not be stable. Only data obtained from the WEAVE Archive System (WAS) can be considered safe for publication.

HARPS3 on the INT

1. HARPS3. The Cambridge-led THE (Terra-Hunting Experiment) Consortium is driving the construction and development of the HARPS3 instrument, for deployment at a newly-roboticised INT. HARPS3 is a high-resolution stabilised spectrograph which will conduct an unprecedented 10-year survey aimed at discovering Earth-mass planets. An instrumental overview can be found here.

   Approximately 60% of time at the INT will be devoted to the THE survey, the remainder being available as open time (for robotic observations with HARPS3 for now) to be allocated by the TACs.

2. Timeline. The INT upgrade, to allow for robotic operation, was completed in 2025, and this mode has now been tested on-sky. The HARPS3 instrument is currently being commissioned at the telescope. First scientific light is expected during the summer of 2026.

3. HARPS3 open time. HARPS3 open time is offered in shared-risk mode in semester 2026B. More details will be published in the 2026B call for proposals. Shared risk in this context means that we make no promises about availability and/or performance of the mode/instrument, given that commissioning is not completed, but we expect it to be completed by the start of the semester.

We welcome your questions, comments or requests for clarification. Please email Ruben Sanchez-Janssen, ING Director (director@ing.iac.es) or Chris Benn, ING Head of Astronomy (crb@ing.iac.es).