The Hubble space telescope was launched on April 24,1990 from Shuttle Discovery in an STS-31. It has optical capabilities of Sensitivity to Light from Ultraviolet through Infrared (115–2500 nanometers). It has two mirrors of 2.4m,828kg and 0.3m,12.3kg and a pointing accuracy 7/1000th arc second or 3.34e-8 rad. That's about the width of human hair from a distance of 1 mile.
Well you are probably thinking why the above the paragraph is about Hubble. Well that's because James Webb is a successor to Hubble. You will need to know why NASA is launching James Webb and what are the changes made.
James Webb Telescope's goals is to look back through time to when galaxies were young. This is possible by observing galaxies that are very distant at over 13 billion light years.
The primary mirror size of James Webb is 6.5m,400kg(compared to 2.4m,828kg of Hubble's).
The secondary mirror is 0.74 meters in diameter.
The Webb Telescope team also decided to build the mirror in segments on a structure which folds up, like the leaves of a drop-leaf table, so that it can fit into a rocket. The mirror would then unfold after launch. Each of the 18 hexagonal-shaped mirror segments is 1.32 meters in diameter, flat to flat.
Webb is what is known as a three mirror anastigmat telescope. In this configuration, the primary mirror is concave, the secondary is convex, and it works slightly off-axis. The tertiary removes the resulting astigmatism and also flattens the focal plane. This also allows for a wider field of view.
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