Comparison between MIRI (at 7.7 microns, 6.5m diameter mirror) and Spitzer (at 8.0 microns, 2003-2020 mission, 85cm diameter mirror). The gain on the Webb image is very visible thanks to its much larger primary mirror and its improved detectors, Spitzer: NASA/JPL-Caltech ; MIRI: NASA/ESA/CSA/STScI
On the evening of the 28th, we could read on NASA's blog: "It's official, the alignment of NASA's James Webb Space Telescope is now complete"!
To say that all the instruments of the James Webb Space Telescope are perfectly aligned, means that the primary mirror is well adjusted. The images are already breathtaking while the adjustment phase of all the elements of the telescope is not finished yet.
For this test, the Webb telescope pointed at a star and the quality of the alignment was verified with a part of the Large Magellanic Cloud providing a dense field of hundreds of thousands of stars on all instrument sensors. Webb's three imaging instruments are NIRCam (images below at 2 microns wavelength), NIRISS (image at 1.5 microns) and MIRI (image at 7.7 microns). MIRI detects light in a lower energy range (or longer wavelength) than the other instruments, revealing the emission from interstellar clouds as well as starlight.
These images are used to assess image sharpness, but also to accurately measure and calibrate subtle image distortions and alignments between the instrument's sensors as part of the overall Webb instrument calibration process.
The sizes and positions of the images shown in the figure below illustrate the relative field of view of each of Webb's instruments in the focal plane of the telescope, each pointing to a part of the sky slightly offset from another.
In the next months, the scientists will continue the commissioning (to characterize the instruments and the stability of all the optics of the telescope without science done). After this step, the scientific exploitation of the data can begin!
JWST/Spitzer comparison: ESA - Sharper view from MIRI hints at new possibilities for science
en savoir plus:
comparaison JWST/Spitzer: ESA - MIRI’s sharper view hints at new possibilities for science