NuSTAR Proposals and Tools

While NuSTAR was initially approved by NASA as a 2-year Principal Investigator-led (PI-led) mission, NuSTAR has now been approved to continue operations through 2022 (subject to further extension by the 2022 NASA Astrophysics Senior Review of Operating Missions) and to have a dedicated General Observer (GO) Program. There are several opportunities for guest observers in the general scientific community to propose for NuSTAR observations.

1. NuSTAR General Observer (GO) Program

Starting in 2014, NuSTAR solicited general observer proposals from the general scientific community. Proposals are solicited via NASA's ROSES grant solicitation process. The proposal process is divided into two phases. A Phase 1 proposal is submitted to NASA HEASARC's ARK system, containing detailed target selection forms and a concise science justification. Proposals may come from both US and non-US researchers. Phase 1 proposals are evaluated by peer review panels. Data from approved GO observations, with the exception of Target of Opportunity (ToO) observations, have a nominal one-year exclusive-use period commencing at the time of receipt of the processed data by the observer. Data from peer review approved ToO observations have a six-month exclusive-use period.

NASA also provides grant funding to support certain selected proposals. These funds are limited to proposals with PIs at US institutions. Selected proposals will receive a notification letter with more details and an invitation to submit a Phase 2 (budget) proposal. Phase 2 proposals are submitted to NASA's NSPIRES system.

Cycle 6 important dates

DateImportant Cycle 6 Event
October 25th, 2019NASA Research Announcement NuSTAR Guest Observer - Cycle 6
Novermber, 2019Cycle 6 phase 1 proposal submissions open
January 22nd, 2020Last day to request assistance for pointings with potential stray light
January 24th, 2020Cycle 6 phase 1 proposals due
late March, 2020Cycle 6 peer review
2. Observatory Guide and Proposal Tools

The NuSTAR project has developed tools and documentation to help potential proposers.

NuSTAR Observatory Guide: The NuSTAR team has developed a document which describes the technical capabilities, concept of operation and key information for proposers. Download the current version NuSTAR Observatory Guide (7.3 MB pdf file) (released June 2016).

Count Rate and Spectral Simulations: The standard HEASARC count rate and spectral simulations tools, WebPIMMS and WebSpec, are available for NuSTAR simulations. WebSpec was updated on March 5, 2014 to include the most recent NuSTAR responses and background files. The NuSTAR responses and background files can also be downloaded directly from the Caltech SOC web site and used to simulate spectra in spectral analysis software such as XSPEC. See Section 4.7 of the NuSTAR Observatory Guide for a detailed discussion of how to simulate NuSTAR spectra using XSPEC. If detailed background modeling is required, the "nuskybgd" NuSTAR background simulation toolkit is is available from the User-Contributed NuSTAR Software page.

Other issues which proposers should take under consideration are:

  • Target Visibility: The NuSTAR Science Operations Center Target Visibility checker allows input of the RA and Dec coordinates of a source and finds the times when it is visible to NuSTAR subject to viewing constraints.
  • Timing: The NuSTAR Clock Correction Files keep the NuSTAR relative time (after barycentric corrections) accurate to ~2 ms and account for drifts in the NuSTAR clock caused by temperature variations, etc. New clock files will be produced as the mission continues on a ~monthly basis.
  • Stray Light: Extremely bright X-ray sources (>100 mCrab in the 3-79 keV band) within 1 to 5 degrees of a target can cause issues with elevated backgrounds due to stray light. The presence of such confusing sources is reported by the NuSTAR Science Operations Center Target Visibility checker.
  • Dead Time: NuSTAR has a triggered readout, similar to a proportional counter but unlike a CCD, so it does not suffer from pile-up effects. However, dead time becomes significant for sources above ~50 ct/s, and this must be factored into integration time estimates. Quantitative estimates of the effect of dead time on exposure estimates are included in the latest version of WebPIMMS. Further details of the effects of dead time on bright source count rates can be found in this memo (pdf).
3. Grant information

Phase 2 (Budget) Proposals

U.S. PI's whose Phase-1 proposals were assigned a Category A or B rating by the peer review panel or accepted in Category L (Large Program) will be invited to submit a Phase-2 (cost) proposal. The detailed instructions are found here.

NuSTAR Guest Observer Program Summary of Research

NuSTAR GOs receiving NASA grants are required to file a Summary of Research Report detailing their supported activities. The report instructions can be found here.

No-Cost Extensions

The information about No-cost extentions on a NASA grant can be found at To request a No-Cost Extension, please complete the electronic form at:

4. Additional opportunities to propose for NuSTAR time

Joint programs through other observatories

Currently NuSTAR has arrangements with various observatories which makes available joint observing time.

Unsolicited NuSTAR Target of Opportunity (ToO) or Directors Discretionary Time (DDT) Observations

A total of at most 500 ks of observing time will be made available to ToO proposals in the GO program. However, unsolicited ToO requests for exceptional transients will continue to be possible through the NuSTAR ToO web site, even for those not accepted into the GO Program. The decision on whether or not to observe a ToO of either category will be made by the NuSTAR Principal Investigator or her official designee. Such ToO requests are unfunded and do not have an exclusive-use period.

If you have any questions concerning NuSTAR or the NuSTAR GO program, visit the Feedback form.