NuSTAR Bringing the High Energy Universe into Focus


Targets of Opportunity

Last Updated: 2020/04/03

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. Note that NuSTAR ToO and DDT observation requests will in general not be considered for events or sources that could have been predicted and proposed for in GO programs. This restriction is being imposed as a result of guidance from NASA's 2019 Senior Review.

In particular, requests for observations of the following types of sources and events require special justification describing why the requested observation type could not have been proposed as a GO target:

  • Known or candidate black hole systems
  • Known or candidate pulsar or magnetar systems
  • Candidate counterparts of gravitational wave or astrophysical neutrino detections
  • Nova or Supernova events
  • Luminosity variations from known or candidate AGN (ioncluding blazars and Tidal Disruption events)
  • Observations of the Sun or other Solar system objects
  • Observations of events with specific time constraints
  • Observations coordianted with other observatories the could have been proposed for to joint GO programs
The decision to perform ToO or DDT 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.