Target of opportunity policy

1. Definition

Targets of Opportunity (ToO) targets are astronomical objects undergoing unexpected or unpredictable phenomena which have not occurred before the dead-line of the call for proposal. They include targets that can be identified before the onset of such phenomena (e.g. dwarf novae, X-ray binaries) as well as objects which cannot be identified in advance (e.g. novae, supernovae, gamma-ray bursts). For the former category, target coordinates are specified in the proposal, while for the latter only the target description is required.

2. ToO allocation and override rights

2.1 Allocation of ToO time
ToO override observations can be requested to and allocated by the Italian (TAC), Spanish (CAT), and OPTICON time allocation committees.

2.2 Override rights of Italian TAC approved ToO proposals
ToO programs approved by the Italian TAC can override observations during TAC and OPTICON nights, within the limits given below.

2.3 Override rights of OPTICON TAC approved ToO proposals
ToO programs approved by the OPTICON TAC can override observations during either Italian TAC or OPTICON nights, within the limits given below.

2.4 Override rights of CAT approved ToO proposals
ToO programs approved by the CAT can only be executed during CAT nights, within the limits described below.

2.5 Nights allocated by other time allocation committees
Nights allocated by the ITP time allocation committee cannot be overridden by any ToO program.

3. Activating a ToO

3.1 Observer of a ToO
ToO observations will be conducted by the TNG staff Astronomer, if present at the telescope. In case the TNG Astronomer is not present, ToO observations will be conducted by the Visiting Astronomer, with the scheduled instrument(s). Non-scheduled instruments may be operated by the Visiting Astronomer, if he/she is willing to use them, or by TNG staff in remote observing from sea level, on a best effort basis.

3.2 Italian TAC and OPTICON proposals
To make sure that all the information is correctly received and processed in time for the observations, override ToO observations for a given night must be activated by e-mail (too@tng.iac.es) before 17:00 UT of the same day. The relevant information on object position and instrument setup, i.e. the observing blocks, should be prepared and submitted using the queuing web interface (Flex) or (for HARPS-N) sending the relevant NSTS files. Please refer to your contact TNG astronomer for more information on the use of these programs.

3.3 CAT proposals
The ToO request should be directly addressed to the scheduled CAT Visiting Astronomer. The observations will be organized and executed by the Visiting Astronomer with the scheduled instrument(s).

4. Observing times and constraints

4.1 Italian TAC and OPTICON proposals
Once a request for ToO observation has been activated, the requested time is subtracted from the time allocated to the program even in case the observation cannot eventually be carried out for bad weather conditions. The requested/allocated time have to include all associated overheads such target acquisition, night-time calibrations and, in case of override on a visiting observing night, the time necessary to reinstall the original instrumental configuration.

4.1.1 Time limits during visitors and scheduled service nights
To reduce the impact of ToO's on scheduled programmes, override observations during visitor or scheduled service runs are limited to

  • only One (1) ToO from each approved ToO program per observing run. For runs longer than three nights, the activation can be repeated after the third night.
  • only One (1) ToO per night. Only the first activation will be executed (but see 5.2)
  • a maximum of 1.5 hours of observation, including all overheads, for each ToO activation.

4.1.2 ToO and time-critical observations
ToO activations cannot override time-critical observations, regardless on whether these are scheduled in visitor or service mode.

4.2 CAT proposals
The amount of time for each ToO request and its override rights are set by the Spanish time allocation committee. For more information please contact the CAT secretary.

5. Special rights and rules for urgent ToO proposals

5.1 Definition of urgent observation (UO)
The P.I. can activate a ToO as Urgent Observation within 6 hours from the event. The P.I. must justify the reasons of UO activation.

5.2 Priority among ToO programs
If multiple ToO activations exist for a given night, the urgent observations will be executed first. The other ToO program(s) might be executed at a later time. In case of multiple urgent observations, priority will be given on a first come-first served basis.

5.3 Activation and override rights of an UO
An UO can be requested at any moment during any TAC or OPTICON night, and can stop any on-going integration. There are no limits on the number of activations of UO.

5.4 Procedure for activating an UO during the night
The P.I. or a pre-identified delegate must phone to the TNG control room (+34 922405535) to activate the UO. In order to provide information on what to observe and how, he/she may

  • remotely use the TNG Flex interface to fill-in the observing blocks
  • provide link to web page(s)
  • send e-mail message(s) (with NSTS files for HARPS-N
  • send a fax
  • use a skype chat

5.5 Time constraints for UO during visitor or scheduled service nights
The limit of 1.5 hour in 4.1.1 is raised to 2 hours per activation.

5.6 Compensation of time lost
Observing programs which lose more than 2 hours due to UO overrides are entitled to an equivalent amount of compensation time which will be executed in service mode on a best effort basis.

5.7 Allocated time for UO
It is computed as described in Sect. 4.1 and includes the time lost by interrupting the on-going integration, if any.

5.8 Transmission of data
The data are available in real time via the IA2 INAF archive.