Target of Opportunity Observations

A target for JWST observation is deemed a Target of Opportunity (ToO) if it is associated with an event that may occur at an unknown time, and in this way ToOs are distinct from time constrained observations.

ToO targets include objects that can be identified in advance, but which undergo unpredictable changes (e.g., some dwarf novae), as well as objects that can only be identified in advance by class (e.g., novae, supernovae, gamma ray bursts, newly discovered comets, etc.). ToOs are generally not suitable for observations of periodic phenomena (e.g., eclipsing binary stars, transiting planets, etc.). ToO proposals must provide a clear definition of the trigger criteria and present a detailed plan for the observations to be performed in the technical justification of the PDF submission if the triggering event occurs. A ToO activation may consist of a single observation or of a set of observations executed with a pre-specified cadence.

ToO response times are specified in the APT Special Requirements. The minimum turn-around time for Non-disruptive ToO activation, without significant impact to the schedule, is 14 days. The minimum turn-around time for Disruptive ToO activation is 48 hours, measured from the time when the activation request is submitted to start of the first observation. Disruptive ToOs can be triggered with turn-around times less than 14 days, provided all of the proposal details (except possibly the precise target position) are available in advance. However, since disruptive ToO observations have a significant impact on the JWST schedule, each cycle (including Cycle 1) will be restricted to a total of 8 disruptive activations. Moreover, due to their scheduling impact, Disruptive ToOs required to be triggered within 3 days will incur an additional overhead of 30 minutes per activation. There is no limit on the number of Non-distruptive ToOs per cycle.

Information on activating an approved target of opportunity program is in JWST Target of Opportunity Program Activation.

Proposers may apply for Long-term status for ToO Programs (for up to three cycles) only if the target phenomena have a low probability of occurrence during one cycle. The request must be justified in the APT Special Requirements


Next: Observations of Targets That Have Not Yet Been Discovered or Identified