The incredible success of the James Webb Space Telescope (JWST) we now witness playing out in space is built on multiple successes on the ground. It took the combined efforts of thousands of people — managers, engineers, technicians, support staff and more — to build and test the observatory. A few of them are shown reflected in the primary mirror shown in the leftmost image. They persevered through unprecedented technical challenges and even a devastating pandemic to complete a virtually perfect JWST.

Credit: from left to right: NASA, Desiree Stover; NASA, Chris Gunn; ESA, M. Pedoussaut; Arianespace, ESA, NASA, CSA, CNES

Perfection is not something that comes naturally to humans, and they needed to adopt a culture of extreme care and self-awareness to come so close! Nonetheless, their work needed to be tested to be sure it would function as planned. Evaluating the performance to be expected by the huge telescope in the cold vacuum of space posed another set of extraordinary challenges. There was a long sequence of critical tests, each of which needed to succeed. The second image from the left shows perhaps the most ambitious. Technicians in the test chamber at Johnson Space Center look tiny compared with the telescope as they finish preparations to close the chamber, pump out all the air, and cool the telescope to its designed operating temperature of 40 kelvin. Three months of testing followed to make sure everything had been designed and built perfectly, or to identify any exceptions for correction.

JWST is an international project, with participation from not only the United States and NASA, but also the European Space Agency, the Canadian Space Agency, and a large number of individual countries in Europe. In fact, only one of the instruments was a USA product — two others came from Canada and Europe and the fourth was a European/USA partnership. But the most dramatic ESA contribution was the Ariane 5 rocket that provided a perfect launch. The image second from the right shows the observatory being mounted on the interface to the Ariane 5 at the Guiana Space Centre. The rocket itself snapped our last view of JWST (rightmost image) as it began its 1.5 million kilometre journey to the L2 Lagrangian point, from which it is now observing the Universe.