The James Webb Space Telescope has successfully deployed its secondary mirror.
This is a new step in the preparation of the James Webb Space Telescope. On January 5, the US space agency announced that the secondary mirror has been pulled out successfully. NASA teams then checked that the tripod that supports it is properly locked, before moving on to the next step. This is again a step that has been successfully completed.
James Webb’s secondary mirror is ready
The secondary mirror is the mirror that collects the light that has been reflected by the primary mirror (which still has to be unfolded in the case of James Webb). This in turn sends it back to the tertiary mirror, then the latter redirects the radiation to a final optical element, the mobile fine pointing mirror. The secondary mirror faces the primary mirror, from which it is “suspended”.
The secondary mirror on board the observatory has a small diameter (0.74 meters, or 74 centimeters) and which is curved – it is a convex mirror, that is to say it is slightly rounded outwards. It allows the light captured by the primary mirror to be focused towards the tertiary mirror and can adjust its orientation using six actuators.
The surface of the mirrors is covered with a thin layer of gold, 100 nanometers thick. This is what gives it its elegant golden hue. In all, gold weighs 48.25 grams – a golf ball. This gold, which is itself covered with a thin layer of glass to protect it, improves the optical properties of the observatory, especially in the infrared.
The placement of the secondary mirror is the second major step in setting up the space telescope. Just before, he completed the unfolding and tensioning of his heat shield, made up of five layers to protect it as much as possible from sunlight. This shield uses a special polymer, which isolates the observatory from radiation extremely well.
The last big step is to deploy the primary mirror and its multitude of segmented mirrors. It will start in a very short time – starting this week – and will run over several days, as there are a total of eighteen parts to install. The telescope’s arrival at its destination is scheduled for the end of January. The start of his operational career will begin in mid-2022.
