WEAVE on the WHT

1. WEAVE. Regular science observations with the WEAVE multi-fibre spectrograph started in October 2023. The observations so far have been with the LIFU low- and high-resolution modes. A standdown for spectrograph realignment began in September 2024 and, as of February 2025, is nearly completed. After the standdown, LIFU science observing, and commissioning of the MOS and mIFU modes, will resume.

   Once the MOS and mIFU modes have been successfully commissioned, a science-verification programme will be carried out. This will be followed by the start of science surveys and open-time access for these modes. The MOS science surveys are expected to begin in late summer or early autumn 2025. Open-time observations with MOS are not offered in this call, but once MOS mode is commissioned, ING might issue a special call for open-time proposals.

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, the availability of other instrumentation (e.g. ISIS, ACAM) in open time is not being considered at present. Observers can safely assume that WEAVE will be continuously mounted on the WHT for 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 at CASU.

   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, but WAS is not yet fully operational. ING recommends that teams wanting to use data from the OR send an email to weave_open_time_support@ing.iac.es so that ING can check with CASU the current status of those data.

INT and HARPS3

1. HARPS3. The Cambridge-led THE (Terra-Hunting Experiment) Consortium is making steady progress in the construction of HARPS3 for deployment at the INT. HARPS3 is a high-resolution stabilised spectrograph which will conduct a 10-year survey aimed at discovering Earth-mass planets. The THE Consortium is carrying out a full upgrade of the INT to allow for robotic operation. 60% of the INT time will be devoted to the THE survey, the remainder being available as open time (most likely for robotic observations with HARPS3) to be allocated by the TACs.

2. Timeline. The INT upgrade started in June 2024, and is now almost complete. HARPS3 will be installed during 2025 and first light is currently expected in September 2025.

3. HARPS3 open time. Progress with the HARPS3 instrument suggests we may be able to offer HARPS3 in open time in semester 2026A.

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

Updated to 15th February 2025