When it was on the ground, the James Webb Space Telescope was the cause of much hand-wringing and debate at NASA. The project encountered numerous setbacks and cost overruns, but it has all paid off in space. After its launch in late 2021, everything has been coming up roses for Webb. Keeping with the trend, NASA now says the telescope is fully aligned, and its vision is perfect, bringing us one step closer to full operational status.
The James Webb Space Telescope (JWST) is the culmination of decades of work at NASA to design a successor for the aging Hubble Space Telescope. That observatory has suffered a series of hardware failures in recent years, and it’s running out of redundant systems with no plans for another servicing mission. Luckily, Webb is proving to be the next-generation window to the universe we hoped it would be. Every phase of the mission, starting with the launch that extended the spacecraft’s life by years, has gone perfectly, and that applies to the now-completed alignment phase.
Unlike Hubble, the JWST uses a multi-faceted Korsch-style mirror. The total surface area is 6.5 meters across all 18 hexagonal segments, which is much larger than Hubble’s single 2.4-meter parabolic mirror. The drawback, however, is that Webb had to fold its mirror up to fit inside the Ariane 5 rocket that blasted it to space. It’s been a painstaking process to align all those segments, ensuring they produce a single image instead of 18 different points of light. This involves making nanometer-scale changes to the angle of each mirror segment. Even a small mistake could cause images to come back blurred.
NASA has been inching toward full alignment for months, starting in March when it announced the primary NIRCAM instrument was perfectly configured. That wasn’t the end of calibration, though. Webb has three other instruments that needed alignment work, plus a “fine guidance sensor” that uses the primary mirror to stabilize images. Now, NASA says all those components are aligned and ready for action. It has provided an amazing mosaic of images from each sensor as proof (above), marking the first time Webb has beamed back proper images from all of its science instruments. NASA says image quality on all the instruments is “diffraction-limited,” which means it’s as good as it can possibly be given the size of the telescope.
Stop me if you’ve heard this one before, but Webb still isn’t quite ready to begin science operations. Up next is a nebulous process known as commissioning. In this phase, NASA will conduct experiments on each detector to ensure they are operating as designed. That way, we know the data they send back is an accurate representation of the universe. The observatory will also be rotated to vary the amount of solar radiation hitting the sunshield. We’re still on track to have Webb fully operational and doing science this summer.