The IXPE GO Program solicits proposals for investigations in any area of astrophysics (not constrained to IXPE’s prime science areas). IXPE Cycle 4 observations will commence on or about February 1, 2027, and continue for a nominal period of 12 months. Individuals may submit proposals for observations that will advance the IXPE mission science return. Observing proposals may be for "standard," "Target-of-Opportunity (ToO)", “Large Program (LP)” or “Multi-cycle” observations. Theory proposals are not solicited. For ToO observations, IXPE anticipates executing approximately 1 high (observations begin within 9 days of trigger) and 7 medium (observations begin between 9 days and 4 weeks of trigger) priority triggers in this GO cycle, hence proposers must strongly justify the response time required to meet the scientific objectives.

The Neutron Star Interior Composition Explorer (NICER) is an X-ray experiment on the International Space Station (ISS) dedicated to high-resolution timing and spectroscopy of rapidly variable X-ray sources in the 0.2–12 keV band. Proposals for NICER data-analysis investigations addressing all areas of astrophysics are solicited, with a limited amount of funding available in GO Cycle 9.

Amendment 57 announces second opportunities to propose to IXPE and NICER General Observer (GO) programs in ROSES-25. The due date for Phase-1 Proposals (submitted via ARK RPS) for both IXPE and NICER is September 17, 2026. The text for these two opportunities may be found in Sections 9 and 10 of D.3 Combined General Investigator General Observer Program.

On or about May 15, 2026, this Amendment to the NASA Research Announcement "Research Opportunities in Space and Earth Sciences (ROSES) 2025" (NNH25ZDA001N) will be posted on the NASA research opportunity homepage at https://solicitation.nasaprs.com/ROSES2025

Programmatic questions concerning IXPE may be directed to Hashima Hasan at hhasan@nasa.gov. Technical questions concerning IXPE may be directed to Kavitha Arur at kavitha.arur@nasa.gov.

Programmatic questions concerning NICER may be directed to Roopesh Ojha at roopesh.ojha@nasa.gov. Technical questions concerning NICER may be directed to Keith Gendreau at Keith.C.Gendreau@nasa.gov.