Heroic Engineering: The James Webb Space Telescope

Minutes

On September 11, 2026, Members of the Society and guests joined the speaker for a reception and dinner at 5:45 PM in the Members’ Dining Room at the Cosmos Club. Thereafter they joined other attendees in the Powell Auditorium for the lecture proceedings. In the Powell Auditorium of the Cosmos Club in Washington, D.C., President Larry Millstein called the lecture portion of the 2,540th meeting of the Society to order at 8:04 p.m. ET. He began by welcoming attendees, thanking sponsors for their support, announcing new members, and inviting guests to join the society. Scott Mathews then read the minutes of the previous meeting which included the lecture by Douglas Wallace, titled “Mitochondria and Their Roles in Health and Disease”. The minutes were approved pending a minor correction.

President Millstein then introduced the speaker for the evening, Jonathan Arenberg, of Northrop Grumman. His lecture was titled “Heroic Engineering of the James Webb Space Telescope: Lessons Learned for Future Flagship Missions”.

The speaker began by characterizing the James Webb Space Telescope (JWST) as an unprecedented achievement in aerospace engineering, requiring nearly 100 million person-hours of effort over several decades. He emphasized that the mission's realization was only possible through a massive international coalition comprising three space agencies: NASA, the European Space Agency, and the Canadian Space Agency, alongside hundreds of academic and scientific institutions and nearly a thousand industrial partners spanning three continents. Arenberg recounted the early conceptual origins of the mission, which could be traced back to the “Next Generation Space Telescope Report” in 1989.

Arenberg explained the primary scientific objectives of the observatory, including: First light & reionization, the assembly of galaxies, the birth of stars & protoplanetary systems, and planetary systems & the origins of life. He said that these objectives strictly dictated JWST’s physical and optical architecture. Because the cosmological expansion of the universe shifts light from distant objects into the infrared, JWST was required to be an infrared-optimized observatory. Observing in the infrared portion of the spectrum dictated that the telescope assembly and instruments operate at cryogenic temperatures to prevent the observatory’s own thermal glow from overwhelming astronomical signals. The near-infrared instruments (0.6-5.0 um) operate below 50 Kelvin and the mid-infrared instrument (5.6-25.5 um) operate below 7 Kelvin.

The speaker discussed the design of the sunshield: five layers of Kapton roughly the size of a tennis court. The sunshield provides passive cooling by maintaining a temperature differential of over 300 Kelvin between the sun-facing side and the cold science instruments. Arenberg described the severe spatial constraints imposed by the launch vehicle, the Ariane 5. Because the required 6.5-meter diameter primary mirror exceeded the approximately 4.5-meter usable envelope of the Ariane 5, engineers designed a deployable primary mirror composed of 18 hexagonal segments made of beryllium, a material selected for its extreme stiffness, lightweight properties, and dimensional stability at cryogenic temperatures. The beryllium segments were coated with a microscopically thin layer of gold to maximize infrared reflectivity.

Arenberg discussed the critical technological breakthroughs required to make the architecture viable. He highlighted the development of actuators behind each mirror segment, providing six degrees of rigid-body motion and radius-of-curvature adjustment with nanometer-scale precision. He explained the implementation of wavefront sensing and control algorithms, which use starlight gathered by the science instruments to phase the individual segments into a single, continuous optical surface. The speaker also highlighted the closed-cycle helium loop cryocooler designed to actively cool the MIRI instrument without expending consumable cryogens.

The speaker then focused on the unique systems engineering and verification challenges inherent in building a system of such complexity. Arenberg highlighted the fact that the team had to rely heavily on rigorous modeling and simulation. High-fidelity structural, thermal, and optical models were developed and validated by extensive testing of subscale models and individual components.

Arenberg showed a series of images and videos, showing portions of the construction, testing, assembly, ground-based deployment, shipment, and finally the launch of JWST on Christmas morning 2021, from ESA’s Spaceport in French Guiana. He showed animations of the 50 deployable structures, successfully deployed over a 14-day period, as JWST made its way to L2, the second Lagrange point.

Arenberg presented early optical alignment results and science imagery, demonstrating that Webb’s optical performance exceeded its pre-launch specifications. He compared several images from JWST with images from Hubble, demonstrating the increased resolution and sensitivity of Webb.

He concluded by synthesizing the major engineering lessons learned, emphasizing that future missions, such as the Habitable Worlds Observatory, must prioritize early investments in critical technologies, integrate rigorous modeling disciplines, and cultivate open organizational communication.

The lecture was followed by a Question and Answer session.

A member asked about the failure risks during the deployment sequence and whether any unexpected anomalies occurred while tensioning the sunshield. Arenberg responded that while the sunshield deployment was historically considered one of the highest-risk phases, it showed exceptionally smooth on-orbit deployment with tension profiles matching predictive models closely.

A member on the livestream asked how the project was funded, and could it happen today. Arenberg responded that JWST was primarily funded from the NASA budget, and that similar projects are being funded today. He specifically mentioned the Habitable Worlds Observatory, which is currently receiving initial funding.

A guest asked what determined the projected lifetime of the detectors on JWST. Arenberg responded that the limiting cases for the lifetime of the entire system were electrical power and fuel (or propellant). He said that all photovoltaic systems show some degradation over time, and that would set the upper limit on useable electric power. He said that JWST uses propellant for course correction and precision repointing.

After the question and answer period, President Millstein thanked the speaker and presented him with a PSW rosette, a signed copy of the announcement of his talk, and a signed copy of Volume 17 of the PSW Bulletin. He then announced speakers of upcoming lectures and made a number of housekeeping announcements. He adjourned the 2,540th meeting of the society at 10:09 pm ET.

Temperature in Washington, DC: 23.9° Celsius
Weather: Passing Clouds

Dinner attendance: 52
Lecture attendance: In person: 107 Live Stream: 45 For a total of 152 viewers
Views of the video in the first two weeks: 1,254

Respectfully submitted,
Scott Mathews: Recording Secretary