Chandra X-ray Center (CXC) Manager’s Report

Mark Weber

Reporting period: November 2023–May 2024

Now in its 25th year, the Chandra X-ray Observatory continues its highly successful science mission. With its unique capabilities for sub-arcsecond X-ray imaging and high-resolution X-ray spectroscopy, Chandra carries out essential observations for many leading X-ray and multi-wavelength investigations in current astrophysical research.

Chandra observing time continues to be highly sought after. Scientists worldwide responded to Chandra's Cycle 25 call for proposals with 408 proposals requesting 4.9 times the total available observing time. The dual-anonymous peer review held in June of 2023 approved 103 observing proposals and 21 archive and theory proposals.

The Chandra Observatory continues to function at or near pre-launch expectations. Incremental changes in the performance of some components continue, generally in line with pre-launch predictions and without hindering operations. The performance of the spacecraft's thermal insulation continues to decline gradually; however, this trend has been mitigated by careful mission scheduling, aided by increasingly sophisticated software scheduling tools. The gradual accumulation of molecular contamination on the UV filter that protects the ACIS detector reduces ACIS's sensitivity to low-energy (below ~1.5 keV) X-rays. Chandra continues to maintain its observing efficiency near the mission-long average of ~70%. (To protect its instruments, Chandra cannot observe during passages through Earth's radiation belts; spacecraft maneuvers, instrument setup, and other procedures necessarily take up a small part of the remaining available time.)

NASA has instructed the Chandra Observatory program (as well as the Hubble Space Telescope program) to take part in an Operating Paradigm Change Review aimed at evaluating the potential science return that could be provided with substantially reduced budgets using revised mission operation models. The Chandra program submitted its information package in April and presented its operational options to the review panel in May.

The Chandra Press Office has been active in issuing image releases, science press releases, and other communications of Chandra research results. A complete listing of Chandra press releases is available at http://chandra.harvard.edu/press.

The approach of Chandra's 25th anniversary in July prompts a look back at the evolution of the program's management. NASA's Marshall Space Flight Center in Huntsville, Alabama, oversees the Chandra program. In 1991, as the result of a competitive procurement, NASA awarded a contract for the Chandra X-ray Center (CXC; then the AXAF Science Center) to the Smithsonian Astrophysical Observatory (SAO) to carry out the scientific functions for Chandra, including soliciting proposals, processing, archiving, and distributing scientific data, and supporting the scientific community. Several years later, NASA determined that science activities and mission operations would be conducted most efficiently if combined within a single organization and expanded the scope of the CXC to include Chandra mission operations. The CXC was also given responsibility for administering the Chandra grants program. The CXC carries out all functions of the program, from soliciting proposals, planning observations, and operating the spacecraft and instruments to receiving, processing, and delivering data, calibrating the instruments, and supporting the science community with data analysis software, scientific conferences, and NASA research grants.

The Chandra management structure, which closely integrates all aspects of the mission, has proven to be highly effective, and it has remained unchanged through significant changes in staffing levels. Since launch, the total number of staff—including MSFC, SAO and subcontractor personnel—has decreased by approximately 42%, in spite of increasing operational challenges due to component aging. Even with fewer staff, the CXC has provided increased levels of utility for the scientific community, such as the innovative Chandra Source Catalog and enhanced functionality and support for the CIAO data analysis software. Maintaining such performance despite the staffing decrease was accomplished by introducing efficiencies and automation in many areas of the CXC. In 2015 an expert panel reviewed Chandra spacecraft operations and determined that the staff level was at approximately the minimum required for a mission of this size and complexity. The 2022 Senior Review of NASA operating missions gave theChandra program its highest rating, “Excellent.”

The Chandra Project looks forward to celebrating Chandra's 25th anniversary with a science symposium this December in Boston and with other events during the year, as well as to many more years of productive scientific discovery.