NuSTAR Target of Opportunity (ToO) or Directors Discretionary Time (DDT) observation request

Submit requests to NuSTAR operations team for review

Fast ToOs (turnaround <= 48 hours) will only be approved for exceptional scientific opportunities

Active ToO/DDT observations
GX 339-42x10 ks in 2019 December and 2020 January (low Solar aspect angle)PI Garcia
NGC 4045 XT-150 ksPI Brightman
NGC 925 ULX-350 ksPI Earnshaw
1RXS J170849.0-4009102x20 ks monitoring at low Solar aspect anglePIs Ray
MAXI J0637-43010x50 ks for NuSTAR GO cycle-5 program 05213PI Tomsick

Please review the NuSTAR schedules for details of upcoming observations and the table of approved ToO programs from the NuSTAR GO program and joint GO programs with Chandra, XMM-Newton, INTEGRAL, and the Neil Gehrels Swift Observatory.

Principal requester
Primary Email address:
      (additional email address can be supplied in Remarks section below)
Best way to reach me:
24 hr Contact info:
Scientific Justification
Object type:
Triggering an approved GO program: If yes, then give mission and GO proposal number:
Scientific Justification:
Relevant URLs
Justification for this particular target:
Likelihood of detection, duration,
and recurrence of transient behavior:
Response time requested: Examples: < 24 hours , < 48 hours , within 1 week , at directors discretion (DDT)

Note that the majority of approved ToOs have response times within 1 week
Justification for requested response time:
Target details
Target Name
RA (J2000 decimal degrees from 0.0 to 360.0)
Dec (J2000 decimal degrees from -90.0 to 90.0)
from until
Date/time format options are described here. Default is UTC, unless you specify another time zone.
Observing time (kiloseconds)
Justification for observing time
(Give details of any source modeling, particularly for exposure time requests above 50 ks)
Expected NuSTAR count rate
(predicted instrument count rate for both modules using 50% PSF extraction with no dead time)

HEASARC WebPIMMS (set "Into:" field to 'NUSTAR') here.
Maximum expected NuSTAR count rate
(in case of flaring, bursts, etc)
Approximate expected spectrum
Source morphology
Coordination with other observatories?:

Clicking the Submit button sends emails and text messages to the NuSTAR operations team. A confirmation email will be sent to the 'Email:' field at the time of submission.

The request will be reviewed by the NuSTAR PI and the operations team and you will be contacted with a decision to approve or decline the request.

NuSTAR data associated with ToO or DDT requests submitted outside of approved GO programs will have no exclusive use period and, when completed, will be available via the public NuSTAR archive. See for more information.

A minimal set of data products for ToO/DDT observations performed within the last 14 days is also available as each observation progresses via the NuSTAR quicklook products webpage. Please carefully read the caveats on the use of this data detailed on the quicklook webpage.

Please contact   nustar-help at   if you have any questions.