December 25, 2021 at 9:20 a.m. local time of the Guyanese Space Center, the European launcher Ariane 5 left the surrounding jungle carrying a 10 billion dollar passenger under his headdress, the James Webb Space Telescope (JWST, also called more simply the Webb).
Merry Christmas from Ariadne!
With its primary mirror 6.5 m in diameter (folded under the cover like the rest of the telescope because of its extraordinary size), the Webb will mark a new stage in astronomy. Dedicated to infrared, the observatory will notably make it possible to see the birth of the first stars and galaxies only 200 million years after the Big Bang. Initiated by NASA, this ambitious program which required 20 years of development associates the Canadian Space Agency (CSA) and the European Space Agency (ESA). These provide instruments and ESA was also responsible for the launch with Ariane 5 built by ArianeGroup and operated by Arianespace. After 27 minutes of flight, the Webb was released from the top stage of the launcher as shown in this video below.
And it is at this moment that Ariane 5 brought, so to speak, a 5 year gift to Webb. Nothing could be more normal after all for a launch on December 25 …
Recall that the JWST embarks in fuel tanks to perform several maneuvers with its own thrusters in order to reach its halo working orbit around the Lagrange point L2 1.5 million kilometers from Earth (far from its infrared radiation so as not to interfere with delicate instruments). The video below shows the principle of this orbit.
In addition, the fuel will also be used for maintain this orbit which is not perfectly stable. From time to time, thrusters will light up to compensate for the inevitable drifts. The quantity of fuel has been calculated for an operational lifetime of the telescope of at least 5 years. Obviously, margins are taken into account to have enough to correct slight errors in trajectory while guaranteeing 5 years of operation. However, the Ariadne 5 gift was a “delivery” on the intended trajectory (we quote NASA) “better than requirements“. Concretely, this means lower fuel consumption by the Webb to get on its way to L2. The savings thus achieved give a surplus which translates into 5 more years adjustments to maintain the halo orbit. The JWST is therefore endowed with 10 years of observation of the universe instead of 5. Merry Christmas!
It should be remembered, however, that the Webb still has to go through many stages in its extremely complex deployment, in particular that of its imposing sun shade as large as a tennis court and that of its 6.5 m mirror folded into 3 parts. The video below explains in animation this route to L2.
About 1 month after its take-off, the JWST will be placed in orbit around L2 and the ground teams will take care of calibrating its optics and its instruments. The first images should be made public within 6 months.