The James Webb Space Telescope is fully aligned. After a full review, NASA has announced that the JWST team has completed the seventh and final stage of telescope alignment. Following completion, the team held a series of key decision meetings and unanimously agreed that Webb’s ready to enter the final series of preparations, science instrument commissioning, ahead of full scientific operations.
The image below shows the alignment of the JWST across all of Webb’s instruments, including NIRSPEC, NIRCAM, MIRI, the Fine Guidance Sensor and NIRISS. The images show a marked change from when Webb detected its first photons in February. At that time, only the onboard NIRCAM, one of four cameras on Webb, was switched on and its image was unfocused. The team has made significant strides in just over two months.
‘Engineering images of sharply focused stars in the field of view of each instrument demonstrate that the telescope is fully aligned and in focus. For this test, Webb pointed at part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, providing a dense field of hundreds of thousands of stars across all the observatory’s sensors. The sizes and positions of the images shown here depict the relative arrangement of each of Webb’s instruments in the telescope’s focal plane, each pointing at a slightly offset part of the sky relative to one another. Webb’s three imaging instruments are NIRCam (images shown here at a wavelength of 2 microns), NIRISS (image shown here at 1.5 microns), and MIRI (shown at 7.7 microns, a longer wavelength revealing emission from interstellar clouds as well as starlight). NIRSpec is a spectrograph rather than imager but can take images, such as the 1.1 micron image shown here, for calibrations and target acquisition. The dark regions visible in parts of the NIRSpec data are due to structures of its microshutter array, which has several hundred thousand controllable shutters that can be opened or shut to select which light is sent into the spectrograph. Lastly, Webb’s Fine Guidance Sensor tracks guide stars to point the observatory accurately and precisely; its two sensors are not generally used for scientific imaging but can take calibration images such as those shown here. This image data is used not just to assess image sharpness but also to precisely measure and calibrate subtle image distortions and alignments between sensors as part of Webb’s overall instrument calibration process.’
Caption and image credit: NASA/STScI
Webb’s optics are not only fully aligned, but they’re also performing better than the team’s most optimistic expectations. NASA writes, ‘Webb’s mirrors are now directing fully focused light collected from space down into each instrument, and each instrument is successfully capturing images with the light being delivered to them. The image quality delivered to all instruments is ‘diffraction-limited,’ meaning that the fineness of detail that can be seen is as good as physically possible given the size of the telescope. From this point forward the only changes to the mirrors will be very small, periodic adjustments to the primary mirror segments.’
The beginning of the final step of Webb’s preparations means that some members of the team are now done working on the project altogether, which is likely a bittersweet moment. Webb has taken many years of year from countless dedicated individuals. Scott Acton, Webb wavefront sensing and controls scientist at Ball Aerospace said, ‘With the completion of telescope alignment and half a lifetime’s worth of effort, my role on the James Webb Space Telescope mission has come to an end. These images have profoundly changed the way I see the universe. We are surrounded by a symphony of creation; there are galaxies everywhere! It is my hope that everyone in the world can see them.
Now that Webb is fully aligned, it’s time for the team to configure and test Webb’s scientific instruments. Each instrument is a ‘highly sophisticated set of detectors equipped with unique lenses, masks, filters, and customized equipment that helps it perform the science it was designed to achieve.’ Key personnel involved with each of Webb’s scientific instruments have convened at the Missions Operations Center at the Space Telescope Science Institute (STScI) in Baltimore, MD.