A mirror built like a flower
The mirror is not monolithic, given that a carrier rocket like Ariane 5 has a third stage diameter, where the so-called payload is housed, a few meters wide and in addition the telescope is brought into orbit even with a protection from the sunlight. also reflected from the Earth, the size of a tennis court.
The main mirror reaches a diameter of 6.5 meters by composing, like the petals of a flower, the 18 hexagonal mirrors with a diameter of 1.32 meters, placed side by side in the ideal position with an accuracy of much less than a millimeter. , an incredible challenge.
A kind of miracle was done to stow it in the last stage of the Ariane 5 rocket, folding it back on itself like an origami, incredible if you think of the 18 mirrors and the metal frame of the telescope, which must close like a bellows. This is also a record: it suggests a butterfly returning to its chrysalis, from which it will then have to exit again when it is in space.
To reopen once in space, Jwst needs almost all the 344 servomechanisms that will guide the delicate operation, and they are all indicated by NASA itself as “single point of failure”, And that means they all have to work perfectly, otherwise the whole process will stop.
The deployment of the telescope also includes that of the shield on which Jwst is practically supported and which protects it from solar radiation, which would blind it immediately. It is the size of a tennis court and made of a very particular material, the Kapton, very light and very thin, much less than a millimeter, and will keep the telescope at a constant -223 degrees, the optimum temperature for its operation.