NuSTAR Bringing the High Energy Universe into Focus


Targets of Opportunity

Last Updated: 2019/06/21

Target of Opportunity (ToO) observations of anticipated astronomical events may be proposed for within the NuSTAR   Guest Observer (GO) program. Additional opportunities to propose for ToO observations are available through the joint GO programs with Chandra,  XMM-Newton, Neil Gehrels Swift Observatory, NICERand INTEGRAL. The data from ToO observations within GO programs have a 6-month exclusive use period for the PI of the GO program, after which the data will be placed in the NuSTAR public archive.

A full list of approved NuSTAR ToO programs is available on the NuSTAR SOC website.

In addition, the NuSTAR project will consider requests for unanticipated ToO observations for exceptional opportunities. Due to the constraints in operations funding, even some exceptional observations may not be possible to implement.

A request may also be made for observations that are not time-critical but need to be performed before the start of the next GO observing cycle. Such requests will be considered through Directors Discretionary Time (DDT) allocation and the decision to perform such observations will be made by the NuSTAR Principal Investigator or her official designee. 

Please use the web form to submit an unanticipated ToO observation or DDT request:

or to trigger an existing approved GO ToO program. If for some reason the website is unavailable then please email nustar _at_ with your request.

Note that a "fast" response ToO is defined as a requirement for observation within 48 hours of notification. These are particularly difficult to implement. ToO observations with longer lead times are less intensive for the operations team and are more likely to be successfully scheduled. 
Data from unanticipated ToO and DDT observations have no exclusive use period and, after validation by the NuSTAR SOC, are placed in the NuSTAR public archive.
The NuSTAR SOC also provides data from ToO/DDT observations while the observation is being performed, updated when new data is downlinked from the spacecraft (approximately four times a day). This quicklook data is available from 
Please carefully read the caveats on the use of quicklook data products that are detailed on the webpage.