James Webb telescope begins crucial sun shield tensioning

The James Webb Space Telescope began one of the most complicated parts of its deployment Monday as NASA sent commands to fully extend the first layer of the observatory's critical five-layer sunshield.

The $10 billion space telescope -- the largest and most powerful in history -- still is in the first half of its 29-day deployment schedule as it flies through space to a position over one million miles from Earth.

Mission controllers worked through two minor issues Sunday that could have degraded performance of the spacecraft over time, according to NASA. But the agency said the space telescope was never in danger and the extra day allowed it to return Webb to optimal performance.

On Tuesday and Wednesday, NASA intends to extend the remaining five layers of the shield, which is the size of a tennis court, spreading them out in a process called tensioning.

The shield provides critical blockage of sunlight from Webb's infrared instruments -- which must be supercooled to function.

After the telescope performs the tensioning of the shield, NASA will have resolved up to 75 percent of the 344 steps in the deployment schedule where a failure could have spelled serious trouble, NASA's Bill Ochs, project manager for the telescope, said during a press conference Monday.

"That is huge in the first week and a half or so of this mission," Ochs said of the progress.

NASA has an aspirational schedule for Webb deployments, but that schedule was always understood to be flexible, he said.

"Nothing we can learn from simulations on the ground is as good as analyzing the observatory when it's up and running," Ochs said. "Now is the time to take the opportunity to learn everything we can about its baseline operations. Then we will take the next steps."

Despite the pause, NASA has confirmed that the rocket launch of Webb from South America on Dec. 25 went so well that the spacecraft itself has additional fuel to surpass its initial 10-year lifespan.

But NASA doesn't know how much longer than 10 years the telescope will last, Ochs said.

"We know it will be a lot more than 10, that's all we can say," he said.

The problems NASA addressed over the weekend were in Webb's power system and in the motors that would be used to tension the sunshield.

Solar power panels were recalibrated and the motors were shield from the sun long enough to help them cool off, according NASA.

Technicians with Northrop Grumman, which built Webb, also helped find solutions to the issues.

"The observatory was never in danger, and we were never power starved," Amy Lo, deputy space vehicle director from Northrop Grumman, said during the press conference.

Rather, Webb was simply not operating at the optimal margins of safety and power that will help it detect galaxies up to 13.5 billion years ago, among other things, for as long as possible, she said.

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James Webb telescope sets off on million-mile voyage
Kourou (AFP) Dec 26, 2021
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