The James Webb Space Telescope has been resupplied: launch time is approaching

Preparations continue for the launch of the large James Webb Space Telescope postponed to December 22, 2021 (after the delay due to a problem during assembly). While in the next few days there will be a definitive integration with the launcher Ariane 5 by Arianespaceat these hours the refueling of the tanks of the JWST extension.


The advent calendar of astronomers according to XKCD (source)

It was a fundamental moment, like others before and those to come, on the way to the second point of Lagrange a 1.5 million km from Earth. The technicians loaded the tanks with the two propellants (hydrazine and dinitrogen tetroxide) capable of moving the telescope when it is separated from the support of the Ariane 5 rocket.

James Webb Space Telescope Resupply

Inside the tanks JWST extension they were accused 159 liters Of hydrazine And 79.5 liters Of dinitrogen tetroxide (used as an oxidant). The operations are quite complicated because we are dealing with toxic and potentially flammable propellants. For this, the technicians had to wear special suits with respirators (SCAPE) and avoid the generation of sparks.

THE space telescope with 12 thrusters which are in the spaceship bus in the lower part of the JWST extension. Although the amount of propellant is not very high, it took 10 days to complete the operations (start-up was on November 25).


Ignition of the rockets using the combination of the two propellants will be used to make course corrections towards the final destination as well as to maintain it once reached. Using only hydrazine will change the targeting area. Currently there are no refueling missions and so once the propellants run out, the James Webb Space Telescope will complete its operational mission.

jwst telescope

The next steps concern moving the JWST extension in the final assembly building (FAB). We will then place it on top of the rocket and close it inside the two fairing. The rocket with telescope will then be transported to the launch pad two days before launch on December 20. But that’s not all. Once launched, it will take 29 days for it to reach its final configuration and a few months for the first observations.

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