Washington, DC; December 10th, 2025
The NATIONAL AERONAUTICS AND SPACE ADMINISTRATION released Amendment 28 to the XRISM Guest Observer Program today; the amendment delivers the finalized text for the next cycle of scientific participation and establishes clear submission deadlines that will govern how researchers, laboratories, and university teams may apply for observational time on the mission. NASA’s announcement presents the newest framework for the scientific community as XRISM approaches its next operational arc, and the agency emphasized that the updated policy text must now be treated as the definitive instruction for all applicants who intend to submit proposals during the coming selection period.
According to NASA, Amendment 28 incorporates refinements gathered from prior proposal cycles; the agency stated that several clarifications were added to improve the precision of proposal preparation, including expanded guidance on target feasibility, data management approaches, and the constraints associated with XRISM’s instrument schedule. NASA reported that the final text harmonizes technical descriptions, streamlines evaluation categories, and ensures that the review process remains transparent, consistent, and scientifically rigorous. The amendment also finalizes the formal definitions of scientific priority tiers, granting applicants a clearer view of how their proposals will be judged.
The agency’s notice confirms that the proposal window officially opens on January 15th, 2026; all submissions must be received by March 15th, 2026. NASA further explained that observation configuration files for approved projects will be due no later than June 1st, 2026; this timeline, NASA stated, is designed to support mission planning, instrument readiness, and coordinated scheduling with partner observatories. The amendment also reiterates the proprietary period guidelines that define when data collected under each approved proposal becomes publicly available, ensuring that scientific teams may analyze their observations while preserving NASA’s principle that funded research ultimately contributes to the broader astrophysics community.
The amendment contains new details describing how researchers may coordinate with other space-based missions when planning multi-wavelength campaigns; NASA noted that these coordinated observations require careful timing, and Amendment 28 now provides more explicit instructions regarding how to request such scheduling preferences. The agency also emphasized improvements to the technical documentation that accompanies the GO program; XRISM’s instrument handbooks have been updated to reflect calibration refinements, expected performance across various energy bands, and the operational limits that may influence long-duration exposures.
NASA stated that a public webinar is scheduled for mid-January; the agency plans to provide a full walkthrough of Amendment 28, answer common questions regarding allowable budget items, clarify the distinctions between archival research and direct observation proposals, and outline the evaluation criteria that the scientific review panels will apply during the assessment period. The agency expressed that this outreach is intended to reduce uncertainty, remove ambiguity, and enable universities, laboratories, and independent investigators to prepare proposals that meet clean, well-understood standards.
NASA emphasized that this amendment represents an essential milestone for XRISM’s scientific future; the agency noted that the Guest Observer Program stands as a principal mechanism through which global researchers may access the spacecraft’s high-resolution spectrometry tools. By providing final text and firm deadlines, NASA aims to foster a research environment that is orderly, equitable, and capable of delivering the maximum scientific return from the mission’s data stream. The agency concluded that Amendment 28 reflects NASA’s continued commitment to transparency and to supporting the astrophysical community with clear, timely, and authoritative guidance.
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Sources
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• NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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