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 2025 (subject to further extension by the 2025 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. NuSTAR data from approved GO observations have a nominal six-month exclusive-use period commencing at the time of receipt of the processed data by the observer. NuSTAR data from peer review approved ToO observations continue to 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 11 important dates

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. US PIs of approved proposals with priority C targets only will be eligible for a $20,000 grant, awarded through NASA's Jet Propulsion Laboratory (JPL), if observations are performed. No Phase 2 budget submission is required for these proposals.

NuSTAR Guest Observer Program Report and Closeout

• No-Cost Extensions/Progress Report

  The information about No-Cost Extensions on a NASA grant administered by the NASA Shared Services Center (NSSC) can be found here (see Section 7.8). To request a No-Cost Extension, please complete the electronic form. A required progress report should be submitted through the electronic form page. For priority C target proposals with an award issued from JPL, requests for a No-Cost Extension including a brief progress statement should be addressed via email to the NuSTAR Project Manager, Dr. Alina Kiessling (alina.a.kiessling [at] jpl [dot] nasa [dot] gov).

• Multi-Cycle Programs/Progress Report

  Multi-Cycle programs are required to submit an annual progress report that is due 60 days prior to the anniversary date of the award, except during the final year of the award. The report must be sent to the Technical Officer for NuSTAR GO grants at nustar_grants@bigbang.gsfc.nasa.gov and Grant Officer at the NSSC at NSSC-Grant-Report@mail.nasa.gov. For award closeout in the final year see Closeout/Final Report.

• Closeout/Final Report

  NuSTAR GOs receiving NASA grants administered by the NASA Shared Services Center (NSSC) are required to file a Summary of Research Report detailing their supported activities along with necessary documentation. The final report is due 90 days after the award period of performance has ended. The instructions can be found here. For priority C target proposals with an award issued from JPL, a final report is required and a template for this report can be found here. This report should be sent via email to both the NuSTAR Project Manager, Dr. Alina Kiessling (alina.a.kiessling [at] jpl [dot] nasa [dot] gov), and the NuSTAR Mission Scientist, Dr. Tod Strohmayer (tod.strohmayer [at] nasa [dot] gov).

4. Additional opportunities to propose for NuSTAR time

Joint programs through other observatories

• Joint Swift and NuSTAR Observations

• Joint XMM and NuSTAR Observations

• Joint Chandra and NuSTAR Observations

• Joint IXPE and NuSTAR Observations

• Joint NICER and NuSTAR Observations

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

Unsolicited ToO or DDT requests for exceptional transients will continue to be possible through the NuSTAR ToO web site, specifically for events or sources that could not have been predicted or proposed for in GO programs. The decision on whether to perform an unsolicited ToO or DDT observation 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.