Another nerve-wracking part…

The Webb team members can indulge themselves. Because the mighty space telescope has managed to unfold and tighten its sun shield without any setbacks; an important milestone. However, we are not there yet. Because now the next nerve-wracking part starts: the implementation of the secondary mirror.

James Webb’s Mirrors

The James Webb is equipped with both a main mirror (consisting of eighteen individual mirrors that act together as one large mirror) and a secondary mirror. The latter is one of the most important parts on the telescope and essential to the success of the mission. And so nothing can go wrong during the unfolding. The ‘small’, round mirror sits on a sort of tripod consisting of three rods and plays a very important role in collecting the light from the main mirror.

The secondary mirror – seen here from behind, on the three rods – faces towards the main mirror. Image: Northrop Grumman

The idea is that the primary mirror collects the faint light from, among other things, the first and most distant galaxies. The secondary mirror then reflects the light collected by the primary mirror into James Webb’s onboard scientific instruments.

Implementation of the secondary mirror

Today it is time for the secondary mirror implementation. In doing so, the tripod, on which the secondary mirror rests, is moved and installed in its operational position. The secondary mirror is located at the end of this ‘arm’. In effect, James Webb “waves” this arm forward to get the secondary mirror directly in front of the primary mirror (see also the video below, minute 1:11).

When the secondary mirror is in the correct position, it will then be the turn of the main mirror. The sides of the main mirror – which each house three of the 18 mirror segments – still have to be unfolded, after which the position of those 18 segments also has to be adjusted to make them function as one main mirror.

Tiny deviation

It is very important that both the secondary and primary mirrors are properly installed. Because a deviation of more than 38 nanometers – one thousandth of the thickness of a human hair – can already cause problems.

So there are still some exciting days ahead. To date, however, James Webb is doing an excellent job. For example, the telescope has already completed 75 percent of the 344 crucial operations. And that as he rushes to his final destination – some 1.6 million kilometers from Earth; an extraordinary achievement. It is, however, a matter of thumb that the following steps will also run smoothly. Because just because of a small mistake, the mission can fail and we may never see beautiful images…