This page summarises override programmes currently active on ING telescopes, and details the protocol by which overrides are triggered and executed. Overrides are triggered by one of the nominated members of the override team, who in the first instance should email the override request, specifying instrument and observation details including finder charts, exposure sequences, dither pattern details and required calibrations, to each of the following ING contacts, and additionally to any ING co-Is on the override programme. The details of the override will then be passed on to the scheduled observer.

Override Contacts
Ian Skillen	wji@ing.iac.es	Overrides and Schedules Manager
Marc Balcells	balcells@ing.iac.es	Director
Chris Benn	crb@ing.iac.es	Head of Astronomy and WHT Manager
Raine Karjalainen	rk@ing.iac.es	INT Manager
Javier Méndez	jma@ing.iac.es	Service Programme Manager
Obs Support Assistants	tog.astro@ing.iac.es	ING OSA Group

The override teams must establish phone contact with the observers prior to the observations being made. This is especially important for overrides triggered out of normal office hours, including weekends and public holidays, and mitigates against internet failures at all times. The relevant phone numbers are:

Phone Numbers
WHT Control Room	+34 922 405 559
INT Control Room	+34 922 405 640
Residencia	+34 922 405 500

Prompt reaction to rapid-response GRB override triggers is important to ensure the scientific goals of these programmes. Target acquisition should commence immediately on receipt of the alert if so requested by the GRB team, and for the other GRB triggers no later than thirty minutes after the phone request, unless a more relaxed observation timeline is confirmed by the GRB team. The response time for any non-GRB overrides will in general always exceed thirty minutes, and will be determined in consultation with the override team.

Override observers should keep a careful note of the details of the observation, including prevailing conditions and seeing, run numbers of the observations and calibrations, and of the total time spent on the override, including all overheads. The data should be copied promptly to the appropriate directory in the anonymous ftp area:

for example, as user whtguest:

• mkdir /obsdata/outgoing/whtguest/20110801/
• cd /obsdata/outgoing/whtguest/20110801/
• cp /obsdata/whta/20110801/"relevant files" .
• gzip *

Please email these details, and the location of the data files, promptly to the override team and to Ian Skillen (wji@ing.iac.es). The override team may then retrieve their data from the anonymous ftp server, e.g. in the previous example, from:

• ftp://ftp.ing.iac.es/whtguest/20110801/

ING thanks all observers for their cooperation in these highly rated override programmes

Observers may not be overridden by more than one authorised programme per night; if multiple override programmes are active, their right to override is prioritised (see below). Overrides are limited to two hours' duration per night including all overheads, distributed in no more than two distinct slots, for example precursor imaging observations followed by spectroscopic observations if quick-look analysis of the imaging data indicates that this is merited.

In the extremely rare event of a subsequent override being requested by the same team within the night for a different target, this is of course constrained by the nightly two-slot, two-hour limit, but otherwise could proceed at the discretion of the scheduled observer.

Observations carried out on scheduled and service nights for TAC-approved override programmes are logged and accounted against their override allocations.

Overrides which require a switch of focal station from that scheduled to carry out the override, e.g. from a Cassegrain instrument such as ISIS, to ACAM at folded-Cassegrain, or from Nasmyth to a Cassegrain or folded-Cassegrain instrument, are of course permitted, but changes to the configuration of a specific instrument (e.g. filter-wheel content, dichroic or grating changes) may only be made with the permission of the observer affected and only if qualified ING staff are available to make such a change.

The following override programmes are active in Semester 2012A:

WHT

W/2012A/3 (Dhillon) is permitted three overrides with ACAM of up to 1.5-hours each, including overheads, for a total of 4.5 hours. It can override service nights and all scheduled UK programmes with the exceptions of W/2012A/25 (Sullivan) and W/2012A/39 (Wheatley), for all moon phases. This programme defers to W/2012A/34 (Levan) on scheduled nights irrespective of which triggers first. Both programmes can, however, be executed on service nights. Overrides will be requested by one of Dhillon, Jonker, Wijnands, Daw, Fender and Stappers.

W/2012A/34 (Levan) is permitted overrides with ACAM, ISIS, LIRIS and Ultracam of up to two hours each (15 hours total), including overheads. It can override service nights and all scheduled UK programmes with the exceptions of W/2012A/25 (Sullivan) and W/2012A/39 (Wheatley), for all moon phases. Late-time overrides for outbursts of age greater than ten days are restricted to service nights, but may proceed on scheduled nights at the discretion of the observer. This programme takes precedence over W/2012A/3 (Dhillon) on scheduled nights irrespective of which triggers first. Both programmes can, however, be executed on service nights. Overrides will be requested by one of Levan, Tanvir, Wiersema, Rol, Gorosabel or other nominated co-I.

w12an001 (Jonker) is permitted three overrides with ACAM of up to 1.5-hours each, including overheads, for a total of 4.5 hours. It can override service nights and all scheduled NL programmes, for all moon phases. This programme takes precedence over w12an012 (Hartoog) on scheduled nights irrespective of which triggers first. Both programmes can, however, be executed on service nights. Overrides will be requested by one of Jonker, Wijnands, Fender, Wijers and Dhillon.

w12an012 (Hartoog) is permitted overrides with ACAM, ISIS and LIRIS of up to two hours each to a maximum of 15 hours, including overheads. It can override service nights and all scheduled NL programmes with the exceptions of w12an002 (Kuijken), w12an010 (Schrabback) and w12an014 (de Mooij), in which cases the agreement of the scheduled team must be given, for all moon phases. Late-time overrides for outbursts of age greater than ten days are restricted to service nights, but may proceed on scheduled nights at the discretion of the observer. This programme defers to w12an001 (Jonker) on scheduled nights irrespective of which triggers first. Both programmes can, however, be executed on service nights. Overrides will be requested by one of Hartoog, Rol, Kamble, Wiersema, Tanvir or other nominated co-I.

89-MULTIPLE-5-12A (Ederoclite) is permitted one trigger with ACAM of up to 1.5-hours, including overheads, at the discretion of the scheduled observer. It can trigger on scheduled CAT and service nights only, when ACAM is available, for all moon phases. Triggers will be requested by Ederoclite.

96-MULTIPLE-2-12A (Trigo) is permitted four triggers with LIRIS of up to 2.5-hours each, including overheads, at the discretion of the scheduled observer. It can trigger on scheduled CAT and service nights only, when LIRIS is available, for all moon phases. Triggers will be requested by one of Trigo, Garcia and Licandro.

126-MULTIPLE-5-12A (Gorosabel) is permitted one override with ACAM, ISIS or LIRIS of up to 1.0-hour, including overheads. It can override scheduled CAT and service nights only with the exceptions of 3-WHT1-12A (Maíz), 21-WHT6-12A (Zapatero), 107-MULTIPLE-2-12A (Negueruela), 135-WHT36-12A (Montañés), 150-WHT39-12A (Garcia) and 163-WHT43-12A (Nortmann), for all moon phases. Overrides will be requested by one of Gorosabel, Castro Tirado, Levan Rol, and Tanvir, or other nominated co-I.

INT

In principle, all scheduled runs on the WHT and INT are subject to overrides, with the following general exemptions and restrictions:

Certain programmes may be protected from being overridden by the TACs; these are listed in the previous section, and only those programmes explicitly listed there are exempt from being overridden.

Programmes allocated time as part of an International Time Programme, an OPTICON programme or an Iranian National Observatory programme (INT only), prefixed respectively by ITP, OPT and INO in the schedules, may not be overridden.

Guaranteed time programmes, prefixed by GT in the schedules, may not be overridden.

AF2/WYFFOS programmes may not be overridden.

Time-critical programmes, including time-critical service programmes, may not be overridden in general, unless specifically directed by the TAC.

Programmes allocated one night or less may not be overridden in general, unless specifically directed by the TAC.

On nights devoted to instrument commissioning, overrides may be carried out at the discretion of the commissioning team.

If competing override programmes trigger an override for the same target and instrumentation on a WHT service night, the override observations will be attempted for the team whose request for the observations is received first. However, in these circumstances the teams may of course elect to share the data. In this event, the time used in the override will be accounted on a pro rata basis to the teams involved, and the duration of the override will be limited to two hours, including overheads.

From time-to-time competing ToO proposals are submitted to the WHT Service Programme. If on a given service night any of the above TAC-approved override programmes elects to trigger an override for the same target as that requested in some Service Programme ToO proposal, the observations will be attempted for the TAC-approved override programme only.

Nights scheduled with adaptive optics allocations are usually annotated as Reference+S/D in the schedules. The S/D aspect of such nights refers to backup for non-AO conditions, and does not represent definite, allocated S/D time, which would be subject to being overridden. The scheduled AO time itself may or may not be overridden in the same way as other programmes, as described in the previous section.