Chandra Announcement: Chandra Cycle 28 Call for Proposals Released 18 December 2025
Tara Gokas
Chandra Cycle 28 Call for Proposals Released 18 December 2025
The CXC is pleased to announce the release of the Chandra Cycle 28 Call for Proposals (CfP). The Call for Proposals, Proposers' Observatory Guide (POG), proposal planning software, and general information are posted on the "Proposer" web page at the CXC website: https://cxc.cfa.harvard.edu/proposer/.
Proposals are due: Wednesday, 18 March 2026 at 6PM (US Eastern Daylight Time)
Proposers are strongly encouraged to carefully review the "What’s New" section of the CfP.
What’s New in Cycle 28
Statement concerning HRC operation: Proposers may be aware that observations with the HRC instrument were temporarily discontinued in late October 2025 due to an anomaly with the high voltage supply for HRC-S. In this CfP, observing proposals utilizing HRC (in any capacity) continue to be solicited. Note that as of the release of this document, a backlog of previous Cycles' HRC observations remains in the Long Term Schedule. Check-out observations have been performed on HRC-I (all performance was nominal) and observations with HRC-I are being resumed in Jan 2026. The return to science for HRC-S will be determined at a later date.
Restriction on single-chip observations with ACIS-S3: Monitoring particle background requires that at least one front illuminated chip is turned on. Previously, observations requesting single-chip observations with ACIS-S3 were considered on a case-by-case basis, however, this will no longer be allowed. This restriction has a minor impact on the minimum frametime achievable with sub-array observations, as described in Section 6.20 of the Proposers’ Observatory Guide (POG).
Policy on the use of Generative Artificial Intelligence (GAI) tools in proposal preparation: Following NASA’s policy on the use of Generative Artificial Intelligence (GAI) tools in proposal preparation, we have added a requirement for reporting the use of GAI tools in the preparation of Chandra proposals. Use of GAI tools must be reported in the references list as described in Section 7.3 of the CfP. To accommodate this change, there is no longer a limit on the number of pages for references. References must start on a new page after the scientific and technical justification and contain no additional content in those pages.
Archival and Theory/Modeling proposals no longer solicited by Chandra: Archival and Theory/Modeling programs are now solicited by NASA through the Astrophysics Data Analysis Program (ADAP) and Astrophysics Theory Program (ATP), respectively.
Reminder that the Chandra Peer Review follows a Distributed Peer Review model: In Cycle 27, the Chandra Review Process transitioned to a distributed peer review model. Each proposing team identifies a team member as the designated reviewer responsible for the review of 10 to 16 proposals. The results of the distributed review are used to inform the selection of most proposals, with Target of Opportunity (TOO), Large Program (LP), and Very Large Program (VLP) proposals undergoing additional panel review that makes final recommendations. Further details can be found in Chapter 9 of the CfP.