NASA opens second NuSTAR Cycle 13 proposal opportunity with January deadline

NASA announced a second opportunity on October 1 for researchers to propose observations with its NuSTAR space telescope during Cycle 13, scheduled to begin around June 1, 2027. Phase 1 proposals are due January 28, 2027. The call matters to scientists seeking telescope time because it sets out the expected observing allocation and removes a previous minimum exposure requirement.

The opportunity is part of NASA’s General Observer program, which solicits basic research relevant to the Nuclear Spectroscopic Telescope Array, or NuSTAR. NASA’s Amendment 76 places the second opportunity within its ROSES-25 research solicitation. The amendment announces the call; the separate Cycle 13 proposer guide supplies the detailed rules applicants will need to follow.

How much NuSTAR observing time is planned for Cycle 13

NASA expects to allocate 11.7 million seconds of observing time to General Observers in Cycle 13, about 73% of the telescope’s total available time. Of that amount, approximately 8.5 million seconds is designated for NuSTAR observations selected through this program element. A further approximately 3.2 million seconds is allocated to joint programs through other observatories. These are planned allocations, not a record of observations already awarded.

NuSTAR’s proposer information divides the time available through this call into up to 6.5 million seconds for standard proposals requesting 500,000 seconds or less and up to 2 million seconds for large proposals. The Cycle 13 guide says a Large Program must request at least 500,000 seconds and may use an additional page to describe the proposed work.

Who can submit a NuSTAR Cycle 13 proposal

Scientists at US and non-US institutions may submit observing proposals, according to NASA’s Cycle 13 guide, which excludes institutions in the People’s Republic of China. Applicants can propose standard observations, Targets of Opportunity or Large Programs. A Target of Opportunity is an observation proposed in advance for a specified astronomical trigger; the guide makes up to 1.5 million seconds of NuSTAR time available for such proposals.

Eligibility for telescope time differs from eligibility for NASA analysis funding. The guide anticipates no more than $4 million to support analysis of accepted targets, and says only principal investigators affiliated with and located at a US institution may receive that funding through NASA. The amount is an anticipated ceiling, not a grant awarded to every successful observing proposal.

What changed in the Cycle 13 proposal rules

The Cycle 13 guide identifies the removal of the former 20,000-second minimum exposure requirement as a change for applicants. Researchers can therefore frame shorter requested exposures under the current rules. The guide also says Phase 1 proposals will undergo dual-anonymous review: reviewers will not initially be told the proposal teams’ identities, while proposers will not know the reviewers’ identities.

The guide requires an anonymized scientific, technical and management document, alongside a separate document describing the team’s expertise and resources. It says reviewers assess the anonymized proposal first and receive the team document after the scientific evaluation. Applicants should use the published instructions when preparing both parts, because the review process places specific requirements on how a team presents its work.

The January 2027 deadline and observing timetable

Phase 1 observing proposals must be submitted through NASA’s ARK/RPS system by 4:30 p.m. Eastern Standard Time on Thursday, January 28, 2027. Researchers who need the NuSTAR Science Operations Center to assess possible stray-light contamination must request that assistance by January 26. The proposer guide says only observing proposals are being accepted at this stage; budget proposals follow for successful applicants in the relevant priority categories.

NASA expects Cycle 13 to run for roughly 12 months from June 1, 2027, and the guide specifies an observing period through May 31, 2028. The mission’s proposer page says NuSTAR has been approved to continue operating through 2028 following NASA’s 2025 review of astrophysics missions. Which investigations receive time, and how much of the planned allocation they use, will depend on proposals and subsequent selection decisions.