Chandra X-ray Center Manager's Report

Roger Brissenden

Reporting period: January 2019 – September 2020

The Chandra X-ray Observatory has carried out more than 21 years of highly successful and productive science operations. Chandra is unique in its capability for producing the sub-arcsecond X-ray images that are essential to accomplish the science goals of many key X-ray and multi-wavelength investigations in current astrophysical research. The Project is looking forward to many more years of scientific productivity. In recognition of Chandra’s important role in high-energy astrophysics, NASA chose to continue the mission and extend the contract to operate the Chandra X-ray Observatory, with science observing potentially through September 2027.

Dr. Patrick Slane, a senior astrophysicist at the Center for Astrophysics | Harvard & Smithsonian (CfA), has been appointed Director of the Chandra X-ray Center (CXC), succeeding Dr. Belinda Wilkes. Dr. Slane has been involved with Chandra since before its 1999 launch, serving in roles including leader of the science mission planning team and as the CXC’s Assistant Director for Science. Dr. Slane received his Ph.D. in physics from the University of Wisconsin at Madison, and he became a research astrophysicist at the SAO in 1988. Having taught high school physics and astronomy prior to his Ph.D. studies, Dr. Slane is particularly interested in science education, and is committed to promoting diverse participation in the study of astronomy, and science generally, at all levels. Dr. Slane’s research interests include the study of supernova remnants, young neutron stars, and pulsar wind nebulae. Dr. Slane began as CXC Director on the 28th of September.

Dr. Wilkes served as CXC Director since 2014, succeeding Dr. Harvey Tananbaum. She joined the CfA in 1984 and has been a part of the CXC for many years, including as deputy leader of the User Support Group and Assistant Director of the CXC. Prior to her work on Chandra, Dr. Wilkes served as a data verification scientist for the Einstein mission and as lead data scientist for the ROSAT program. As CXC Director, Dr. Wilkes oversaw many major accomplishments for the mission, including two highly successful Senior Reviews conducted by NASA, the move of the Chandra Operation Control Center to a new state-of-the-art facility, the multifaceted celebration of the mission’s 20th anniversary for both the scientific community and the public, and the extension of the CXC contract with NASA. Dr. Wilkes has recently been selected as a Fellow of the American Physical Society.

The Chandra Operations Control Center (OCC), from which we conduct mission operations, has successfully moved from its previous site in Cambridge, MA, to Burlington, MA. Following testing and readiness reviews, operations in the new facility began in May 2019.

Since March 2020, Chandra science and mission operations have been challenged by the coronavirus (COVID-19) pandemic. CXC staff have adapted to a new environment in which working from home is the norm (with a minimum level of staff physically at the OCC and the science center to carry out spacecraft communications and computer system operations). Our primary goals are ensuring the health of our staff and maintaining the continued normal operation of Chandra. Protocols and schedules are in place to keep operators physically and temporally separated and to properly clean the OCC. In the next phase of response to the pandemic, procedures have been instituted to increase the number of staff in phases, maintaining reduced occupancy and physical separation.

Normal operation of the spacecraft, and processing and distribution of data, have continued unabated. In June the Chandra Director’s Office conducted the annual peer review of proposals via remote access. In addition, operations staff and instrument scientists responded effectively to two spacecraft anomalies during the pandemic. Both were resolved successfully with staff working from their remote locations. In May 2020 the spacecraft transitioned to safe mode due to a timing error in the command sequence. No hardware was involved and Chandra returned to science within a few days. In August, a hardware anomaly in the High Resolution Camera instrument required staff to turn off the HRC. After careful analysis, planning and review, the HRC’s control electronics were swapped to its redundant circuits. (Chandra is equipped with duplicate sets of electronics and hardware for many functions.) Procedures have been carried out to return HRC to full observing, which will be completed after checkout of the HRC-S configuration. HRC has resumed its role of providing radiation protection for the instruments, and the ACIS instrument is carrying out normal science observing.

The Observatory continues to operate extremely well overall, but with a number of incremental changes in performance. The gradual accumulation of molecular contamination on the UV filter that protects the ACIS detector reduces ACIS’s sensitivity to low-energy X-rays (but does not affect the HRC). Overall spacecraft heating due to the slow degradation of Chandra’s multi-layer thermal insulation requires extra effort in scheduling observations, but has not significantly affected Chandra’s observing efficiency.

Chandra Source Catalog version 2.0 (CSC 2.0) was released to the community in October 2019. CSC 2.0 is the second major release of the catalog, and represents a significant improvement over its previous version in terms of sky coverage, sensitivity and capabilities. The catalog includes measured and derived properties for 317,167 unique compact and extended X-ray sources in the sky, allowing statistical analysis of large samples as well studies of individual sources. The catalog is discussed in greater detail in a separate article in this newsletter.

In response to the December 2018 call for proposals for Cycle 21 observations, scientists worldwide submitted 516 proposals, including 426 proposals for observing and 90 for archive and theory research. The observing proposals requested a total of 89.2 Msec of telescope time, an oversubscription factor of ~4.6. The Cycle 21 peer review, held in June 2019, approved 142 observing proposals and 26 proposals for archive and theory research.

The call for proposals for Cycle 22 observations, which was issued in December 2019, resulted in 519 proposals, including 426 proposals for observing and 93 for archive and theory research. The observing proposals requested a total of 9.5 Msec of telescope time, for an oversubscription rate of ~4.3. The Cycle 22 peer review, held remotely in June 2020, approved 142 observing proposals and 22 proposals for archive and theory research.

The project conducted a highly successful symposium, “20 Years of Chandra Science,” in Boston, December 3-6, 2019. The symposium, which hosted 300 attendees and was broadcast in real time via Twitter, included poster and science sessions, as well as a panel discussion featuring astronauts who flew the Space Shuttle that launched Chandra.

Two new books also celebrate Chandra’s 20th anniversary. A handsome “coffee table” book, Light from the Void, filled with beautiful Chandra images, some combined with data from other great observatories and large telescopes, was published by Smithsonian Books in the fall and is available on Amazon. In addition, a ~500 page review of Chandra and its science, The Chandra X-ray Observatory: Exploring the High Energy Universe, was published by IoP as part of their series in collaboration with the AAS.

The CXC held a workshop, Chandra Frontiers in Time-Domain Science, during October 2020. The workshop, which was conducted via remote access, featured 36 invited speakers. A summary of the workshop can be found in a separate article in this newsletter.

The Chandra Press Office has been active in issuing image releases, science press releases and other communications of Chandra research results. A complete listing is available at Information about the Chandra Observatory and the Chandra X-ray Center can be found at