The multi-layer sun shield is unfolding this week. The portion extending forward from the telescope body will be extended later this week.
The sun shield for the James Webb Space Telescope is 12 x 22 meters. It can't be sent to space in that configuration. As a result, the launch will be followed by weeks of equally nerve-wracking days as different parts of the observatory are gradually unfolded.
The process has begun and everything has gone off without a hitch so far. NASA analyzed the results of the initial firings of the observatory's on-board rockets and found that it will have enough fuel for a decade of operations.
Good news on fuel.
The L2 Lagrange point is a site about 1.4 million kilometers away from Earth. To get into that orbit, you have to move outside the plane defined by the Earth's orbit around the Sun, and arrive at a shallow angle.
The initial course set by the Ariane 5 launch vehicle and a series of course adjustments powered by its onboard engines are what the Webb is relying on to reach the appropriate trajectory. The onboard engines will be responsible for making adjustments to keep the Webb in its position. The more efficient the first bits are, the more fuel can be used.
The controllers of the Webb have analyzed the results and the amount of fuel used from the two course-correction firings. Their results? The observatory should have enough propellant to support science operations for a long time.
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The Ariane 5 launcher, which exceeded the minimum requirements needed to put Webb on the correct course, was largely credited by the team.
The launch vehicle's performance explains why the solar panel deployed sooner than expected after the observatory separated from the launch vehicle. The panels could deploy whenever the telescope reached the right orientation to produce power. The launch vehicle did a good job of orienting the Webb and this led to the rapid extension of the panels.
Unfolding drama-free.
The process of putting the Webb into its operational configuration has continued. The first two of the five processes that will make up the final configuration of the sun shield are complete. It was folded in half around the telescope hardware and stowed for launch.
The front and rear portions of the sun shield have now been unfolded, bringing the shield to its full length for the first time. The next step will be to extend the left and right sides, then separate out the different layers of the sun shield and add tension to make them bigger. The process will take about five days to complete.
With the sun shield at least partially functional, NASA has now added temperature data to the "Where is Webb?" tracking website. Without the sun shield at its full extension, the observatory's hot and cold extremes are different by over 160o C.
There is a hardware change happening as this story is being written. The telescope sits on a pedestal that raises it above the sun shield and gives it a greater field of view. The Deployable Tower Assembly was in a small position for launch, but it is now being put in a fully extended configuration. It could take as many as six hours for NASA to complete this process.
