The tension is high for the telescope.
The tension on the sun shield was tightened on Monday by the controllers of the James Webb Space Telescope.
The task should take up to three days to complete. The tensioning was delayed by two days as engineers took a break for the New Year's Day holiday.
Bill Ochs, the project manager at NASA's Goddard Space Flight Center, said during a phone call with reporters Monday that they were not surprised by the delay. We take a very close look at things we can't see on the ground to make sure we understand.
NASA's James Webb Space Telescope mission is live.
The James Webb Space Telescope works in pictures.
If that goes to plan, engineers will continue tensioning the first layer of the sun shield through Monday. The following four layers will be adapted by the team once complete. The schedule calls for the deployment to finish on January 5, but the timing of layer tensioning may be different depending on the engineering data that is produced during its sequence.
The sun shield is a vital component of the observatory. The Hubble Space Telescope successor will need to be ready for gathering data from a distant point away from our planet in a month.
As it executes the deployment, it is making the journey to its destination, which is a stable area called sun-Earth Lagrange Point 2 (L2), which allows the spacecraft to "park" with a minimum of fuel usage. Engineers can make pauses in the deployment procedure to assess any issues that arise because most of the deployment steps are controlled by the ground.
A graphic shows the sun shield of the James Webb Space Telescope. The image is from NASA.
Engineers spent an extra day studying the power subsystem of the telescope to make sure it was ready before tensioning the first layer of the sun shield. They found two issues that were within the scope of the telescope's engineering parameters, but they wanted to double-check.
There was a set of six motor that was used for sun shield tensioning. Engineers reoriented the motor because they had a slightly higher temperature than expected.
The motor temperature dropped as expected after the shading procedure. "We like to have a lot of operating margin for our motors, and in fact, for anything we do," said Amy Lo, observatory alignment thread lead at the same press conference.
The previous temperature spike was well within limits, at a peak motor temperature of 327 degrees kelvin. The temperatures were initially expected to be around 116 Fahrenheit or 47 Celsius, but the motors are rated as high as about 150 Fahrenheit or 67 Celsius. "We have a lot of operating margin," he said.
The solar array output affects the power of the man. A preset "max duty" cycle in an array regulator module was limiting the available voltage and not allowing the resources it needed for ongoing observatory activities.
The duty cycle shows the ratio of time a circuit in the solar array is on compared to the time it is off. The team always planned to change the cycle after the launch, but they decided to do it earlier than they were supposed to because they could see how the observatory operated.
The temperature of the array determines the duty cycle's variance. If the temperatures in the array are higher than expected, this leads to lower efficiency and a lower duty cycle limit.
The issue was drawing down the battery more than expected. While engineers worked on the issue, power output remained positive and the house was never power starved. The solar array's duty cycles were changed by the engineers.
An animation shows the final planned trajectory of the James Webb Space Telescope. The image is from NASA.
The power change in the duty cycle was only as high as 65 to 69 volts, depending on the array, compared with the factory preset of 58.6 volts. Engineers verified that the fix would work in the factory's simulators. The simulations showed that all was well.
The issues during deployment were all within the range of expected, as the satellite is just stretching its legs in space. He said that the models that they do pre-launch match what they see on the ground, but occasionally they see something that is not quite matched.
"You want to understand what you're looking at, make sure it's not a problem," he said. We've been spending a lot of our time with that. It goes back to understanding the characteristics of the craft that we never anticipated, based on testing and so forth on the ground.
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