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

These are proposals of a non-claimstaking nature for a well-defined set of observations in response to a trigger which is unpredictable in time. Such proposals are encouraged if they are specific and helpful for planning a response. They are evaluated by the Time Assignment Committee and assigned a scientific priority. If triggered they may displace any lower ranked proposal at the discretion of the Program Director for ATNF Scientist or the Lead Scientist for the facility in question. The Time Assignment Committee may impose limits on the maximum number of triggers in any given term. As the follow up situation may change following a trigger event, either the TAC or the Director may reassess a NAPA proposal at any time once the observations have begun.

In some cases, NAPA proposals may be granted a 'pre-graded' (continuing) status. In this case the Time Assignment Committee will specify the length of time for which the proposal grade will remain valid (normally for one year.)

To submit a NAPA proposal you should use OPAL to complete and submit an ATNF observing proposal form together with a full scientific case. NAPA proposals for the ATCA are assigned standard proposal numbers C***, for Parkes P***, and for the LBA, V***.

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, 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