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Teams working in Northrop Grumman’s spacecraft factory in Southern California have connected the spacecraft and science modules of the James Webb Space Telescope for the first time, a major milestone as engineers prepare to verify a fix to tears in the observatory’s sunshield, and begin launch vibration and acoustic testing in the coming months.
Technicians at Northrop Grumman’s facility in Redondo Beach, California, mated JWST’s telescope with its spacecraft bus Aug. 23. Since then, workers have been finalizing mechanical and electrical connections between the two main elements of the observatory, the most capable space telescope ever built.
“This is a huge milestone for us,” said Eric Smith, JWST’s program scientist at NASA Headquarters in Washington. “This is a program that was first kind of in people’s minds about 30 years ago. Some of the initial contracts went out in 2001 and 2002, and to see it in that clean room now is breathtaking. A lot of people have waited a long time for this. It’s wonderful to see.”
Set for launch from French Guiana aboard a European Ariane 5 rocket in March 2021, the James Webb Space Telescope will cost more than $10 billion by the time its mission is complete, including contributions from NASA, the European Space Agency and the Canadian Space Agency.
NASA is bearing the bulk of the cost at around $9.7 billion. ESA is providing instrument hardware and a launch vehicle for Webb, and Canada built the fine guidance sensor and a spectrograph for the observatory.
“This is an exciting time to now see all Webb’s parts finally joined together into a single observatory for the very first time,” said Gregory Robinson, the Webb program director at NASA Headquarters. “The engineering team has accomplished a huge step forward and soon we will be able to see incredible new views of our amazing universe.”
A crane lifted Webb’s telescope element over the spacecraft bus and sunshield, and carefully lowered it into place. There are six mechanical attach points between the science module, which includes Webb’s telescope and science instruments, and the spacecraft bus, plus around a dozen wiring harnesses, each routing numerous data and electrical cables, Smith said
Once teams complete the connections, they will unfurl the observatory’s tennis court-sized sunshield, a thermal barrier designed to keep Webb’s sensitive infrared detectors cold.
Made of five Kapton membranes, each as thin as a human hair, the sunshield is designed to deploy to its open configuration once Webb is in space. The membranes are coated with aluminum and treated silicon to reflect heat away from the observatory, keeping Webb’s instruments as cold as minus 370 degrees Fahrenheit, or minus 223 degrees Celsius. Internal coolers will chill some of the telescopes’s sensors even colder.
Engineers found seven tears on the sunshield membranes during a previous deployment test, and a tensioning system used to hold the membrane into its shape developed too much slack during the test, creating a snagging hazard, NASA said.
Since discovering and repairing the sunshield tears, ground teams put the spacecraft element, which holds the sunshield, through a series of vibration, acoustic and thermal vacuum tests to expose the hardware to the shaky, noisy, cold, airless environments it encounter during launch and in space.
“They will now deploy the sunshield to make sure that it behaves as expected after going through the launch (environments),” Smith said Wednesday. “They’ll release all the membrane devices and push out the booms for the sunshield, and tension up the membranes.
“That’s one of the things they certainly will be looking for, is having gone through the environments, what’s the shape of the sunshield coming out of those?” Smith said. “Were the procedures that they put in place to correct some of the things that caused some tears last time, did they work as planned? That’s very much a part of this deployment test.
“They also needed to make some adjustments to the so-called membrane tensioning system, the system of pulleys that actually tighten up the sunshield,” Smith said in an interview with Spaceflight Now. “So they made those adjustments, and we’ll be seeing did that do what we needed it to do as well.”
The test crew at Northrop Grumman will also deploy other structures on the telescope, then put the entire observatory through electrical, vibration and acoustic tests. After those checks are complete, technicians will unfurl the full observatory once more to make sure all the mechanisms survived the launch environment testing.
Then technicians will stow the observatory into launch configuration.
The observatory folds up origami-style to fit under the Ariane 5 rocket’s payload shroud. Depending on how you count, Webb will have more than 300 deployments after it separates from from the upper stage of the Ariane 5 launcher. Counting steps in a similar way, the Curiosity Mars rover had around 70 deployments, according to NASA.
Named for James Webb, the NASA administrator from 1961 through 1968, the new observatory will be stationed nearly a million miles (1.5 million kilometers) from Earth, using a 21.3-foot (6.5-meter) mirror and four science instruments to peer into the distant universe, studying the turbulent aftermath of the Big Bang Seed, the formation of galaxies and the environments of planets around other stars.
