Since the James Webb Space Telescope’s launch last December, engineers have worked to deploy the telescope’s hardware and then align both the mirrors and instruments. Now that months-long process has been completed and the telescope has been confirmed to be fully aligned. NASA and the European Space Agency have shared an image showing the sharpness check of all Webb instruments, showing that they are all clear and well focused.
“Technical images of sharply focused stars in the field of view of each instrument show that the telescope is fully aligned and in focus,” writes the European Space Agency. “For this test, Webb pointed to part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, which provides a dense field of hundreds of thousands of stars across all of the observatory’s sensors. The dimensions and positions of the images shown here reflect the relative arrangement of each of Webb’s instruments in the telescope’s focal plane, each pointing at a slightly offset portion of the sky relative to each other.”
Technical images of sharply focused stars in the field of view of each instrument show that the telescope is fully aligned and in focus. NASA/STScI
The four instruments in question are the Mid-Infrared Instrument (MIRI), the Near-Infrared Camera (NIRCam), the Near-Infrared Spectrograph (NIRSpec) and the Near-Infrared Imager and Slitless Spectrograph/Fine Guidance Sensor (NIRISS/FGS) . † That’s three imaging instruments and one spectrograph (an instrument to detect the composition of objects by separating the light they give off), but the spectrograph can also be used to create images – such as the images shown above used for calibration and target selection. If you look at the NIRSpec image, you can see black bands across it, which are caused by the microshutter array that allows it to open and close small windows, allowing the instrument to observe up to 100 objects at once.
All four instruments were aimed at the same target, so technicians could check that they were all as sharp and accurate as needed. And the results are even better than the engineers had hoped, resulting in high image quality, meaning the instruments are diffraction limited – meaning they get the maximum amount of detail possible for the size of the telescope.
With the alignments complete, the team can now begin commissioning each instrument. That includes configuring and checking parts of the instruments, such as the masks and filters, to ensure they are ready for scientific operations. Some final calibration processes for the telescope are also required, such as checking that the telescope remains at a constant temperature when moving from one target to another. Once all this is done, the telescope will begin science operations this summer.