Leaving Earth at the end of December, the James Webb telescope has already covered about 90% of the distance that separates it from its destination, 1.5 million kilometers away.

James Webb is no longer very far from its destination: according to the tracking site set up by NASA, which makes it possible to know where is the telescope in space, the observatory has practically covered 90% of the distance which separates it from its point of arrival, the Lagrange point L2 of the Earth-Sun system, which is 1.5 million km away.

The telescope should be on site at the end of January 2022, in about ten days. In anticipation of its arrival, its cruising speed has been significantly reduced along the water: it only travels at almost 300 meters per second, whereas it was still speeding at 1 km/s at the start of the year — and even more during the start of its journey through space.

James Webb unfolds the segments of his mirror

The opening of the telescope is also continuing and has entered its final phase: all that remains is to deploy all the segments that make up its primary mirror, which requirespower no less than 132 motors. And it’s done at a very, very slow pace, just a few millimeters : 12.5 mm within the next ten days. As for the alignment, it will take place over the next three months.

NASA also offers another tracking tool which makes it possible to view this first sequence of the deployment of the mirrors.

At 12.5mm, the mirrors are in the stowed position. At 0, they are deployed. // Source: Screenshot

At the end of January, James Webb will not yet be ready for service: once well placed in its orbit, the telescope will enter a crucial calibration phase which will last five months. It will also be at this time that the machine will take the opportunity to lower the temperature of its scientific instruments. It is in the summer of 2022 that the first observations will be able to begin.

James Webb’s primary mission is to last five years. Therefore, it is expected that during this period it will provide useful data for the objectives assigned to it. That said, we now know that the telescope can serve ten years in total, even twenty years, thanks to the quality of the take-off of Ariane 5. Good news, which partly mitigates the delays and additional costs of the project.

For further

The primary mirror at the time of its installation on the ship.  // Source: Northrop Grumman via Flickr (cropped photo)



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