1. Overview

This NASA Research Announcement (NRA) solicits General Observer (GO) proposals for NuSTAR. Approximately 8.5 Ms of time will be available in the observing period June 1, 2025 - May 31, 2026, subject to the mission being extended beyond September 2025 after the 2025 NASA Astrophysics Senior Review. It is anticipated that no more than $4M in funding will be made available to support the analysis of targets accepted at priority L, A, B or C. Priority C targets will be observed on a "best-effort" basis. Target proposals will be considered from both US and foreign PIs. NuSTAR data from approved GO program observations (including peer review approved ToO observations) have a nominal six-month exclusive-use period commencing at the time of receipt of the processed data by the observer. Only PIs affiliated with, and located at, a US institution will be eligible for funding for accepted NuSTAR proposals through NASA. As part of the NuSTAR Cycle 11 program, up to 1.5 Ms of XMM observing time, up to 300 ks of Swift observing time, and up to 250 ks of NICER observing time will be made available for coordinated observations with NuSTAR.

2. Deadline

Proposals are due no later than January 29 (Wednesday), 2025 4:30pm (EST).

Note that the last day to request assistance for pointings with potential stray light to NuSTAR SOC is January 27th, 2025.

3. What's New in Cycle 11

New: NuSTAR Cycle 11 observing time available for ToO proposals has been increased to 1.5 Ms.

Reminder: Dual-Anonymous Review Proposals

Dual-anonymous peer review (DAPR) means that not only will the proposers not know who their reviewers are, but the reviewers will not know who the proposers are, at least not until after they have evaluated the scientific merit of the proposal. This implementation of DAPR will be based on that employed by STScI in the evaluation of Hubble Space Telescope observing proposals in recent cycles, in that the names of team members will ultimately be revealed to the peer review panel after all of the proposals have been reviewed for scientific merit. At that time the peer reviewers will have the opportunity to comment on the qualifications and capabilities of the team. The selection official will take into consideration the assessment of the team's qualifications when making the selection.

The primary motivation for reviewing proposals in a dual-anonymous fashion is to minimize unconscious bias in the review process. PIs should consult the Guidelines for Anonymous Proposals document in the "Other Documents" section of the NuSTAR solicitation on NSPIRES for instructions on writing proposals appropriate for a dual-anonymous reviews.

• Proposals should eliminate language that identifies the proposers or institution, as discussed in the Guidelines for Anonymous Proposals.
• PIs are required to upload a one-page "Team Expertise" PDF through ARK as a separate upload when submitting the anonymized Scientific/Technical/Management section. (Note that, for NuSTAR proposals, the page limit for the team expertise document is one page, i.e. further constrained compared to "no more than three pages" from the general guidelines document.) This document provides a list of all team members, their institutional affiliations, roles, expertise, and contributions to the work. The document should also discuss any specific resources that are key to completing the proposed work. If a change of the exclusive-use period from the 6-month default is requested (expected to happen infrequently), a compelling justification e.g., protecting the timely completion of a graduate student's thesis, needs to be added in this document.
• Proposals that do not follow these dual-anonymous guidelines may be returned without review.

Reminder: Coordinated Observation Requests

4. Proposal Elements and Submission Method

Additional details concerning Cycle 11 are given in the NuSTAR NRA. There will be a two-phase proposal process. Phase one is for observing proposals. Phase two is for budget proposals for successful phase one proposers who were awarded priority L, A or B targets. Only observing proposals will be accepted at this time.

Proposal submission is done via the HEASARC ARK/RPS on-line system. Hard-copy submission is not required. The following elements are required:

The following should not be submitted:

5. Some Key Details of the Proposal Form

New NuSTAR PIs must first create an ARK account and/or join the NuSTAR RPS group. Having done so, the NuSTAR RPS form can be accessed via ARK/RPS.

We provide below some key details for NuSTAR Cycle 11. For further details, consult the ARK/RPS help file.

Cover Page

• Institutional endorsement is not required by NASA in NuSTAR phase 1 proposals. Use the endorsement-related entries only if they are required or desired by the PI's institution.
• A total of up to 2 Ms of NuSTAR Cycle 11 observing time will be made available for the Large Program (LP) category. The minimum total exposure time for LP proposals is 500 ks.
• In addition to investigations utilizing NuSTAR observations only, proposals involving coordinated observations with the XMM-Newton observatory, NICER observatory, and/or Swift observatory can also be proposed during Cycle 11. Proposals for joint NuSTAR-XMM, NuSTAR-NICER or NuSTAR-Swift observations should be indicated by clicking the Joint proposal section of the ARK/RPS form, and inputting the requested XMM, NICER, and/or Swift exposure time in each target form. Proposers may submit the same proposal to XMM AO-24 and NuSTAR Cycle 11. However, the XMM-Newton AO-24 approved program will be taken into account during the NuSTAR Phase 1 review and duplicate observations of the same targets by NuSTAR will typically not be awarded. Similarly, Proposers may submit the same proposal to Swift AO-21 and NuSTAR Cycle 11 as well as NICER AO-7 and NuSTAR Cycle 11. However, the Swift AO-21 and NICER AO-7 approved program will be taken into account during the NuSTAR Phase 1 review and duplicate observations of the same targets by NuSTAR will typically not be awarded. All joint time proposals need to include a NuSTAR component.
• Joint proposals for NuSTAR observations with Chandra, IXPE, or XRISM, cannot be submitted in response to this AO. However, NuSTAR does have separate agreements with Chandra and IXPE for coordinated observations. Please see the main Proposals and Tools page for more information.
• Target of Opportunity (ToO) proposals will be accepted in response to this AO.

General Form

• To facilitate checking for conflicts of interest during the peer review process, the co-I's institution must be chosen from the menu (thereby enforcing a uniform set of names). Please check the list of institutions and contact the RPS team as soon as possible if your co-I's institution is not on this list.
• Up to 30 co-investigators can be entered into the RPS form. However, only the first 15 co-investigators will appear on the cover page PDF. The full list will be used by project personnel for conflict checking. Under the Dual Anonymous Proposal Review Procedure reviewers will not see any investigator names provided to ARK/RPS, unless they assess them after ranking the proposals (see the DAPR Guidelines). Please do not enter any investigator names in any ARK/RPS comment fields.

Target Form

• Time Constrained: A target is considered as "Time Constrained" if any of the following sections of the target form are marked as 'Yes':
  • Position angle dependent
  • Moving Object
  • Monitoring Program
  • Phase Dependent
  • Date Constrained
  • Multi-year
  See the NuSTAR RPS help page for more information about these fields. In addition, observations coordinated with other ground- or space-based observatories are considered as time constrained.

  Time-constrained observations designated Category A, B or L will be given highest priority for scheduling during Cycle 11 (or Cycle 11 and 12 for multi-year programs). Time-constrained observations of Category C targets will be executed on a best-effort basis and therefore should be scientifically justified if the time constraint is not satisfied.

  The time constraints for a multi-year program can occur in Cycle 11 and/or Cycle 12.

  Note that time-constrained Category A, B or L observations that are not part of a multi-year program and are not scheduled during Cycle 10 may be carried over to Cycle 11 where warranted by scientific or operational circumstances (e.g., in the case of coordinated observations with other space- or ground-based observatories). Category C time-constrained observations not scheduled during Cycle 11 will not be carried over to Cycle 12.

• Proposers should include a summary of details that are necessary for scheduling and observation planning (constraints, observing mode) in the Remarks box for each target.
• Sources with fluxes > 10^-11 ergs s^-1 cm^-2 within 5° of the target may cause increased non-uniform background gradients due to stray light. Users should check observations for potential stray light contributions using the tool that is available at the NuSTAR SOC web site. If a field is designated as having a "Potential stray light issue", proposers should submit a request for a feasibility analysis to nustar-help@srl.caltech.edu at least 2 business days prior to the proposal submission deadline.
• The minimum exposure for NuSTAR targets is 20 ks. If the proposer is also requesting XMM, NICER, and/or Swift time, the minimum exposure times for these telescopes are 5 ks, 1 ks, and 1ks, respectively.
• Estimated Count Rates: Expected total band (3-79 keV) count rate of the source in counts/second for both modules in a 50% PSF extraction with no deadtime.
• Target of Opportunity (ToOs): A total of up to 1.5 Ms of NuSTAR Cycle 11 observing time will be made available for proposals to observe ToOs. Single-trigger ToOs that are part of a Large Program are not held to a 1.5 Ms exposure time limit. Please note that regular ToOs do not carry over into Cycle 12.

  Proposals with a preferred response time less than 48 hours will be evaluated based on the assumption that the minimum response time is 48 hours. A more rapid response time than 48 hours will be accommodated on a best-effort basis.

  For ToO observations that are to be triggered from a class of objects: Complete one target form per trigger only, specifying "0.0" for both the R.A. and Dec. fields and providing a generic target name, and, if applicable, enter a list of potential target names in the ToO Remarks field. If the list of targets is too long to fit in the TOO Remarks field, include the list in the anonymized Scientific/Technical/Management section instead and put a note in the ToO Remarks to look there for the list.

  For ToO observations that are to be triggered from a list of specific named objects: Complete one target form per object and trigger criterion even if you ask for time for a subset only. For each ToO proposal the "Maximum Total Time Requested for ToOs" field must be provided. If you ask for time for a subset only, this number will be smaller than the automatically calculated summed exposure time for all target forms.

  Please note that it is the responsibility of the PI of an accepted ToO proposal to alert the NuSTAR SOC when the trigger conditions for their accepted ToO have been satisfied (via http://www.nustar.caltech.edu/page/too_policy). For more details see AO section 1.3.4.

After completing all fields for a proposal in ARK/RPS, use the Verify button to confirm that all required entries exist and conform to the expected format. Forms that pass verification can then be submitted. ARK/RPS allows PIs to continue to modify submitted proposals until the deadline, so there is no penalty for submitting the proposal form early.

The LaTeX, PostScript, and PDF buttons of ARK/RPS can be used to generate formatted versions of the proposal forms. Although it is often useful for the PIs to keep formatted copies of the forms for the record, it is not a required part of the proposal submission process.

6. Anonymized Scientific/Technical/Management Section

Format

• The anonymized Scientific/Technical/Management section for a standard and ToO Program must not exceed 4 Letter size (8.5" x 11") pages. The anonymized Scientific/Technical/Management section for a Large and/or Joint Program must not exceed 5 pages. Page limits include figures but not references.
• The anonymized Scientific/Technical/Management section can be generated using the software of the PI's choice, as long as it is converted to PDF format before submission. However, the font size and margings should meet the proposal style format requirement described in the ROSES Summary of Solicitation. Specifically, the text body font size should be no smaller than 15 characters per inch. A 12 point font size is recommended. Please note that Phase-1 proposals should have a single-column format. References should be in the [1], [2] format.
• Proposals must not contain hyperlinks to additional material other than references to public information that do not identify the PI, Co-Is or their institutions; web pages with material specific to the proposal such as target lists or stray light assessments are not allowed.
• We suggest that proposers use the LaTeX template or the Word template for the anonymized Scientific/Technical/Management section. When using these templates, the user should double-check that the text area is 6.5" x 9", having at least 1 inch top, botton, right and left margins on US letter size paper (8.5" x 11").

Content

• Proposals should include a description of the scientific objectives; justify the choice of target(s); show that existing data (previous X-ray observations or at other wavelengths) are insufficient to achieve the objectives; justify the choice of NuSTAR over other existing observatories (preferably linked to some unique characteristic of NuSTAR); and demonstrate the feasibility of the proposed observation and analysis.
• Proposals for targets already observed by NuSTAR are allowed, but must include a justification for an additional observation, such as a much longer exposure, different pointing position within an extended object, or different observing window for a variable object. Observed and/or approved NuSTAR targets can be found using the HEASARC/Browse numaster table or by using NuSTAR As-Flown Timeline.
• Conflicts with Legacy Survey Targets
  Observations of targets accepted through the Cycle 11 Call for Proposals will take precedence over legacy program observations of those targets. The status of legacy survey target observations can be found in HEASARC's numaster table by selecting "EGS", "ELS" or "GLS" for the obs_type keyword.
• A list of approved NuSTAR ToO programs in the NuSTAR, joint NuSTAR/XMM, joint NuSTAR/Chandra, joint NuSTAR/Swift, and joint NuSTAR/INTEGRAL GO programs can be found on the NuSTAR SOC page.

• The length of the observation should be justified based on the specific scientific objectives, preferably using simulations or scaled from prior NuSTAR observations of a similar source. However, the minimum NuSTAR observing time for a target is set at 20 ksec.

7. Expertise and Resources - Not Anonymized Document

8. Phase 2 (Budget) Proposals

US PIs whose Phase-1 proposals are assigned a Category A or B rating by the peer review panel or accepted as a Large Program, i.e., Category L, will be invited to submit a Phase-2 (cost) proposal. US PIs of approved proposals with priority C targets only will be eligible for a a small flat rate grant, awarded through NASA's Jet Propulsion Laboratory (JPL), if observations are performed. No Phase 2 budget submission is required for these proposals.