NASA completes test of James Webb part separating spacecraft mirrors
The US space agency NASA has completed a new important test of the James Webb telescope. A part of the construction was tested that separates the telescope part with the mirrors and the instruments from the relatively warmer spacecraft part.
The Deployable Tower Assembly is not visible here
During the test, the so-called Deployable Tower Assembly was gradually extended to a length of 1.2 meters over the course of a few hours. This is exactly the maneuver that will also take place in space for the James Webb telescope to function. According to NASA, the test passed and the tower performed exactly as predicted.
It was the first time that this part of James Webb has been tested in a ‘flyworthy’ configuration. For example, in previous tests, the telescope assembly was not yet fully assembled. In order to simulate the weightless conditions of the space as closely as possible, all kinds of pulleys and counterweights were used during the test, in combination with a special crane, called the gravity-negation system. According to NASA, all Earth’s gravity effects were successfully removed during the test.
The Deployable Tower Assembly is in fact a tower that forms the basis that, among other things, attaches the gold mirror segments of the primary mirror to the lower part of the entire structure. Once in space, this tower is extended to create as much space as possible between the spacecraft section and the telescope section. This also makes it possible to unfold the large sun shield. This is much needed, because James Webb’s mirrors and sensors have to operate in particularly low temperatures: -266 degrees Celsius. This makes it possible for James Webb to focus on infrared light from very distant stars.
This tower construction is not only important for keeping the sensors and mirrors cool. It also plays an important role in keeping James Webb compact and allowing him to fit into the nose cone of the Ariane 5 rocket. That’s no superfluous luxury, because James Webb is about the size of a tennis court and would never fit in the Ariane 5’s 5.4m fairing when fully extended. James Webb was specifically designed to be launched with this ESA rocket. That launch has been postponed several times and is still planned on paper for March next year, although it is obvious that that period will not be met either, partly because concerns about Covid-19 have delayed certain testing work.
The graphite Deployable Tower Assembly. This part is made by Astro Aerospace, part of the American company Northrop Grumman Company. When fully extended, the tower measures three meters.