As it hurdles through space, NASA’s Webb telescope has successfully completed another step in its multi-month bootup process: it has deployed its secondary mirror. While secondary may sound less important, this mirror is crucial to Webb’s mission.
For space imaging, Webb’s primary, and visually striking, honeycomb-shaped primary mirror is designed to catch as much light as possible. It reflects this light down to a smaller focal point, right where the secondary mirror is located. The secondary mirror then reflects the light back towards the center of the primary mirror where the telescope’s sensing instruments are. The light can then be processed and recorded to form images of faraway space. Without the secondary mirror, all Webb could do is reflect light back into space.
The secondary mirror resides at the end of a 7-meter (or 23-foot) long tripod, appropriately named the Secondary Mirror Support Structure (SMSS). After unfolding from the honeycomb structure, the SMSS had to “lock itself into place to a tolerance of about one and a half millimeters.” There was only one attempt possible for the system to deploy, so it is fortunate, and a mark of solid engineering, that no error occurred to disrupt the process. From now on, as Webb finishes its deployment and begins imaging space, the SMSS will have to hold itself tightly in place through the spins and turns of the space telescope.
According to the JWST deployment explorer, the completion of secondary mirror deployment is the 18th step in Webb’s unfurling. Over the next few days, Webb will progress through six more steps and complete its instrumental deployment. All the while it will continue its journey to Earth’s L2 point, the destination it is scheduled to reach within two and a half weeks. There Webb will find a stable orbit location free from light pollution and obscuring atmospheric particles where it can begin mapping the stars.
Banner Image Source: NASA/Northrop Grumman
Article Image Source: NASA/Northrop Grumman