Target of Opportunity and NAPA Information


The ATNF Time Assignment Committee recognises two types of proposals for which observations need to be scheduled at short notice; Target of Opportunity and Non A-priori Assignable Proposals.


Non A-priori Assignable (NAPA) Proposals

Target of Opportunity (ToO) Proposals

Recent ToO observations for Parkes, ATCA, Mopra and LBA

Payback Time

Data Access


Non A-priori Assignable (NAPA) Proposals

Non-A-Priori Assignable (NAPA) projects can be proposed through the normal TAC process. They should specify a well-defined set of observations in response to a well-defined set of triggers that are unpredictable in time. No claim-staking of a source, or class of sources,  will be permitted.​

The TAC will evaluate these proposals on their scientific and technical merits and assign each a scientific priority. In the normal semester scheduling process, a cutoff grade is established whereby most projects with that TAC grade were scheduled most of their time. If a NAPA project is graded equally to or higher than this cutoff grade, it is presumed that it would have been eligible to get time, if the trigger time were known. Therefore, any NAPA project graded equally to or higher than this cutoff grade may displace any other scheduled observation. Any NAPA project graded lower than this may be scheduled in unallocated time.​

Any project, regardless of grade, may be scheduled at the discretion of the Facilities Program Director or Space & Astronomy Director. Except in exceptional circumstances, maintenance time and reconfiguration time cannot be displaced for a NAPA observation. A NAPA trigger for either ATCA or Parkes cannot displace time allocated to the LBA without explicit approval from the Directors. A trigger for an LBA NAPA may displace scheduled time at the ATCA and Parkes however, if the grade of the LBA project would have normally seen that project scheduled.​

If requested and approved, a NAPA project may be allowed to use the ATCA rapid-response service, which can automatically respond to a trigger within seconds. In this case, no other NAPA will be able to use the service until the minimum required time (normally 2 hours) has elapsed to ensure that the  data is scientifically useful, as defined by the investigator. After this exclusionary period, and while the triggered project is still being observed, only higher-ranked projects may use the service, except at the discretion of the scheduler or the Directors. The rapid-response service must not be used to obtain time on the telescope for observations other than those described in the science justification supplied to the TAC.​

The TAC may impose limits on the number of triggers for a NAPA project, or on the total amount of scheduled time that it may displace. After a trigger, the TAC or the Directors may reassess a NAPA proposal at any time, if they feel that the science situation has changed from the original proposal.​

In the case that more than one NAPA project wishes to trigger on the same event and source, and at the same time, the scheduler, the Directors and/or the TAC may assign an impartial expert to design and carry out observations that satisfy the scientific requirements of all the triggering projects. The data from these observations would be shared between the teams, and the trigger will count towards the allocation of each project.​

In the case that more than one NAPA project wishes to trigger at the same time, but for different events and sources, the project with the higher TAC grade will be preferred by the scheduler. This does not preclude the scheduling of the other projects at other times, if requested.​

NAPA proposals may be granted "pre-graded" (continuing) status by the TAC, usually for one year (including the semester in which it was proposed). If the NAPA trigger condition is unlikely, this pre-grading may allow the triggers to be used even if they happen after the end of the semester, without requiring the proposal to be resubmitted. If a trigger is used, but the timing of the proposed follow-up observations would take them into the following semester, pre-graded status makes that possible. If, however, an event requires follow-up observations more than a semester after the trigger, then a separate normal proposal should be submitted for this purpose.​

Any sale of telescope time to be allocated at short notice (that is, in a “NAPA” style) will be on a basis that leaves flexibility for approved NAPA and ToO requests to take precedence, and minimises impact on National Facility users. In particular, there is no intention to allow automated overrides for paying users. CASS has no intention of allowing paying users exclusive access to particular targets or science goals that would inhibit access to National Facility users.


Target of Opportunity (ToO) Proposals

These are unexpected astronomical events of extraordinary scientific interest for which observations on a short time scale are justified. ToO observing time is allocated at the discretion of the ATNF Director and may displace other scheduled observations at short notice. To avoid conflicts of interest, ToO requests are cross-checked against existing observations and proposals.

To apply for ToO observing time on ASKAP complete the ASKAP TOO Observation Request Form (

For all other facilities send an email to the ATNF 'alert' group ( Your email should include a scientific justification (approximately one page) and sufficient technical detail for the observations to be scheduled. Applications will be judged against these criteria.

ToO Approval Criteria

Responding to a request for Target-of-Opportunity telescope access involves answering the following questions:

  1. Are the requested observations urgent?
    • Is there a time-critical aspect to the scientific question, such as the time variability of the object concerned?
    • Is it in the interests of the scientific community to answer the question quickly; for example to contribute to a new and topical discussion of great scientific interest?
  2. Is the requested observation technically and operationally feasible?
    • There may be telescope facilities normally offered, but not available at short notice;
    • Operational resources may not be available for the proposed observations.
  3. Is the scientific merit of the proposal sufficient to commit telescope resources?
    • There is an operational cost, even if the telescope would otherwise not be engaged in astronomical measurements.
  4. Does the scientific merit of the proposal exceed that of the scheduled observations that would be displaced by granting the ToO observations?
    • This is a question of scientific judgement and the Director may choose to contact the TAC chair or other TAC members for advice on this question.
  5. Are the proposers of the ToO observations willing to make the data public immediately (within 1 week)?
    • It is a condition of using telescope override observations that the normal 18 month proprietary period be waived.

If there is an affirmative answer to all these questions the ToO time will be granted. The Director may choose to modify the precise details of the requested observations for scientific, technical or operational reasons.

If your proposal is approved, you will be notified by the Program Director of ATNF Science, or delegate, who may request further information to assist with scheduling the observations. If your proposal is not accepted you will similarly be advised.

ToO proposals for the ATCA are assigned proposal numbers CX***. Information on exisiting ToO proposals and observations taken can be obtained from the ATNF archive databases. To find all ToO records enter CX as the project identification.


Payback Time

A reasonable attempt will be made to replace time lost due to override by a NAPA or ToO proposal, or to equipment failure. Time lost resulting from poor weather, observer errors or remote observing link failures will not be replaced. The following guidelines apply :

  • In the case of degraded data, the amount of replacement time will be at the discretion of the Program Director for ATNF Science.
  • Lost time will only be replaced if the time, array configurations and receivers available are scientifically appropriate.
  • Generally, replacement time will be scheduled during unallocated slots. At the Program Director for ATNf Science's discretion, replacement time may also be scheduled during scheduled maintenance. Replacement time cannot displace other scheduled observations.
  • Once allocated, a replacement slot will take on the status of a normally scheduled observation and may be displaced by a higher ranked NAPA or ToO proposal.
  • When nearing a proposal deadline, if there is little or no prospect of replacement time being available before the start of the next term, then the proposal should be resubmitted to the TAC. The TAC's assessment would then be used for further time allocation.

Data Access

Observers displaced by ToO or NAPA observations have no special rights to the data.

Results from ToO or NAPA observations should be made publicly available as soon as possible via an appropriate astronomy alert service (e.g. IAU Circular, Astronomers Telegram, Gamma Ray Burst Coordinated Network (GCN). If results are not made available within a week of the observations, then the raw data may be released to other groups.

The full ATNF policy on release of ToO and NAPA data and results is given in the document ATNF Data Access and Archives.

For further information on preparing and submitting ATNF telescope applications, please refer to How to Apply for ATNF Telescope Time.


Page last updated: 20-apr-2018 pge