The CMB-S4 Director’s Review was held on November 14-17, 2023, to assess the project’s readiness in preparation for Department of Energy (DOE) and National Science Foundation (NSF) conceptual design reviews, both anticipated in 2024.

CMB-S4 Infographic

CMB-S4 Infographic (Click to enlarge). Credit: Samantha Trieu, Berkeley Lab

CMB-S4 (the Cosmic Microwave Background Experiment – Stage 4) is a next-generation experiment being pursued as a joint DOE and NSF project to precisely map the cosmic microwave background with unprecedented sensitivity. CMB-S4 will answer key questions about the origin of our Universe. (Click on the CMB-S4 Infographic, right, to learn more.)

The project was recommended as a high priority in the National Academies Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020) and as a top priority in the 2023 P5 Report recommendations, released last week. Once past the conceptual design phase, the project will proceed to the detailed engineering design of the 12 state-of-the-art microwave telescopes, which will survey the sky with close to 500,000 cryogenically-cooled superconducting detectors, located at the best sites for CMB observation in the Chilean Andes and at the South Pole.

The external review committee consisted of experts from academic and research organizations nationwide. Natalie Roe, Associate Laboratory Director for Physical Sciences, welcomed participants and encouraged the committee to review the project with ‘a fine-toothed comb’ and to provide the invaluable and constructive feedback needed to guide the project towards success in the next level of reviews.>

The Director’s Review lasted four days with three full days of presentations by the project team. The committee evaluated science requirements and systems engineering approaches plus technical design decisions and progress to date across all CMB-S4 subsystems. Construction, installation, and commissioning plans at the remote observing sites were also reviewed. In addition, strategies for the highly advanced data analysis pipeline to evaluate the CMB signals were discussed. Two separate subcommittees evaluated project cost and schedule plus the management team of this large and complex project.>

CMB-S4 Project Manager Matthaeus Leitner hosted the review and coordinated the team’s presentations. “It is a great pleasure to work with such a distinguished team of CMB scientists and engineers who have optimized the experiment design over many years of diligent work. Big project reviews are a strenuous effort, and I want to thank everyone for their dedication to CMB-S4 and for helping us push the project forward.”>

In their final report, issued on November 30, the review committee congratulated the project team on the impressive progress that has been made since the previous Director’s Review in November 2021, especially in light of the limited funds available. The committee complimented the project team’s exceptional work on the science-driven technical design, their “strong and experienced” management team, as well as various documentation and planning elements that are “very advanced for this stage” in the project’s review process.>

“These reviews are critical milestones in a big project like CMB-S4,” said Roe. “The extensive preparations help to focus the team, and the in-depth discussions and recommendations provide crucial guidance to keep the project on track. This review was very successful in all of these aspects.”

CMB-S4 Project Director Jim Strait, who has a long history of managing large international scientific projects, is enthusiastic about the outcomes of the review and the committee’s constructive recommendations. “The Director’s Review was very successful,” Strait said.  “It both validated that we are on track for upcoming funding agency reviews and gave us many recommendations and words of advice that will ensure that we will be ready for the NSF and DOE reviews once they are scheduled. The Review Committee was fantastic.  They were very constructive in their interactions with us while holding our feet to the fire.”

CMB-S4 Director’s Review – Group photo taken on November 14, 2023 (Credit: Thor Swift).