Overrides at the AAT

Override Policy

Applications for overrides should be submitted to the Australian Time Assignment Committee (ATAC) in the same way as other applications. They will be assessed on scientific merit in the normal way. An override can take several different forms. The most obvious is an observation of a target of opportunity (ToO). This is defined as any observation where the notice given to the AAO and the scheduled observers is likely to be short. Applications for such projects should be submitted in the usual way, explaining why the science can only be done in this fashion. However, any other short observation requiring less than half a night may also be treated by the AAO as an override.

Therefore, a scheduled observation requiring two hours after twilight for three consecutive nights is also treated as an override. In this case though, the scheduled observers will know in advance, and compensation is normally given for the time lost.

The following special rules apply to all override projects:

  • As much notice as possible should be given to the scheduled observers that their program would be subject to an override.
  • Any scheduled observing program may only be overridden once. There is therefore the potential for conflict between two or more override proposals. In all cases, the override program which is triggered first shall have priority. Resolution of any disputes will be the sole responsibility of the Director, or his designate.
  • There should normally only be one override per program (i.e., one single time slot) without compensation from ATAC. If you wish to ask for an exception to this rule (e.g., you want several short exposures on the same target spread over several nights), you should make this clear in the technical case, and in the scheduling comments part of the application forms. Such cases will be considered by ATAC on an ad hoc basis, but they will be expected to set a total maximum length of time that these observations should not exceed during a single block of time. That block will then be considered as one override.
  • Observers would normally be compensated through Director's time or through the normal scheduling process where possible for programs where more than one override was scheduled. However, no compensation would be made where the same observers would be participating in the scheduled program and the override program.
  • If a ToO override requests more than a single override during the time of a single allocated project, the Director must be informed by the group calling the override. If agreement cannot be reached between the observers at the telescope and the group calling the override, the Director's discretion is final. All such overrides are counted against the originally allocated maximum set by ATAC for a given semester, and observers suffering such additional overrides will be given compensation.
  • Overrides may take place during Director's Time or on Service Nights. These still count towards the total allocated by ATAC however.
  • The override would be deemed to have been completed regardless of poor weather or any other obstacle which might effect observations (if you are seeking a ToO override, you are of course allowed to check what the weather is before calling for the override!). The current weather conditions at the AAT are available here.
  • Override programs will only be executed after a complete observing checklist, full contact details, and template observing sequences (where appropriate) have been provided by the Principal Investigator, to the satisfaction of the AAO Director. To assist in this process, an AAO contact astronomer will be assigned to each approved override program.
  • Within 2 days of the conclusion of an override observation, the Principal Investigator is obliged to contact the Director (director -@- aao.gov.au) and the AAT Technical Secretary (aatts -@- aao.gov.au) with the details and the outcome of the observations.

Lee Spitler aatts@aao.gov.au