The Webb Telescope Completes Alignment Phase
It is official, alignment of NASA’s James Webb Space Telescope is now complete. The alignment of the telescope across all of Webb’s instruments can be seen in a series of images that captures the observatory’s full field of view.
Featured in this video are engineering images demonstrating the sharp focus of each instrument. 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 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 the instrument sensors as part of Webb’s overall instrument calibration process.
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