James Webb Space Telescope

After the deploy the two main mirror sides the real tricky part starts. They will be test and adjusting each of the 18 segments of the mirror. Each segment has 6 actuators to move it around to focus the mirror and a 7th in the middle to adjust the shape. That is scheduled to take 11 days to complete.

After thinking about why they made this mirror so complicated I decided that it is likely because of what happened with the Hubble. They didn't count on it's mirror warping and had to use a shuttle mission to install a device that essentially gave it a pair of glasses. That would not be possible with the Webb so they had to come up with a way to focus the mirror remotely.