After the launch of the James Webb Space Telescope on December 25, 2021, all subsequent transactions have proceeded as planned and now the JWST extension it is in orbit around the L2 point where it will remain for the next few years (for a minimum of 5 years but with the possibility of reaching up to 20 years). We know, however, that it is still too early to think of seeing a good image in the infrared. It will take about five months for the next steps.
The first image that the large space telescope could capture once alignment steps are complete will likely focus on the Large Magellanic Cloud. For the alignment of the mirrors (primary and secondary) instead the JWST extension will point its instruments in the direction of the star called HD84406 in the constellation Ursa Major. What will happen in the weeks to come?
The James Webb Space Telescope and instrument cooling
As explained by Nasa in the last post dedicated to JWST extensionto complete the alignment of the mirrors (especially the primary mirror with its 18 segments) it will also be necessary to cool the scientific instruments. NIRS Specification, NIR camera, FGS/NIRISS and MIRI they will operate at very low temperatures to prevent the heat (and therefore infrared) produced by the instrumentation itself from interfering with the readings.
As the space agency reminds us, MIRI and other components of the James Webb Space Telescope they had already been lit a few weeks after launch. NIRCam, NIRSpec and FGS/NIRISS were rather partially operational and it was only in the last few days that engineers completed ignition operations. We will now proceed to shut down the heaters (to prevent the condensation present at launch from freezing and causing problems) to allow the instruments to begin cooling to operating temperatures.
MIRI for example, it will run at only 7K (approximately -266.15°C) with an additional liquid helium cooling system. Other tools, including NIR camera, which will be used for mirror alignment, will operate at -153°C. These are extremely low temperatures and this is one of the reasons why sun protection was thought of. In addition, in the rear area of the main mirror there is ADIR (Aft Deployed Instrument Radiator), a radiator that will serve to dissipate some of the heat.
Initially, engineers will see HD84406 as 18 different stars due to misaligned mirrors. At this point, thanks to NIRCam, it will be possible to start aligning the 18 segments with an accuracy of a few nanometers to arrive at the final position. A long and delicate process that will require the months that separate us from the first post-calibration image. In the meantime, the most curious can use the new tool on the official website of the James Webb Space Telescope (JWST). In category “Where’s Webb?” » it is now possible to plot the position of the telescope in the solar system (by clicking on Webb in the 3D solar system) and to see how it moves in relation to the Earth, the Sun and other planets.
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