Teams working in Northrop Grumman's spacecraft factory in Southern California have combined the spacecraft and science modules of the James Webb Space Telescope for the first time. Northrop Grumman's plant in Redondo Beach, California has this JWST telescope connected to the spacecraft bus on August 23. Since then, employees have completed the mechanical and acoustic testing electrical connections between the two main elements of the observatory, the most powerful space telescope ever built.
"This is a great milestone for us," said Eric Smith, JWST program scientist at NASA's Washington headquarters. "This is a program that first appeared in people's minds about 30 years ago, with some of the first contracts signed in 2001 and 2002, and it's breathtaking to see them in that clean room, and many have been waiting for it for a long time It's wonderful to see. "
The launch of the James Webb Space Telescope from French Guiana aboard a European Ariane 5 rocket in March 2021 will cost more than $ 10 billion by the time its mission is completed Contributions of NASA European Space Agency and Canadian Space Agency.
NASA contributes the bulk of the costs at approximately $ 9.7 billion ESA supplies instrument hardware and a launcher for Webb, and Canada has the fine-line sensor and a spectrograph for the Observatory built.
for the first time, "said Gregory Robinson, Webb program director at NASA headquarters." The engineering team has a large SC progressed forward and soon we will be able to see unbelievable new views of our amazing universe. "
Webb's spacecraft and science modules have been individually tested in various assembly steps over the past decade. Now it's time to test the entire observatory in one piece.
A crane lifted the Webb Telescope element over the spacecraft's bus and sun visor and gently lowered it into position. There are six mechanical connection points between the science module, which includes the Webb telescope and science instruments, and the spacecraft bus, as well as about a dozen wire harnesses, each laying numerous data and electrical cables. You unfold the sunshade of the observatory in tennis court size, a thermal barrier that protects Webb's sensitive infrared detectors from the cold.
The sun visor consists of five Kapton membranes, each as thin as human hair. Once Webb is in outer space. The membranes are coated with aluminum and treated silicon to reflect the heat away from the observatory and keep Webb's instruments as cold as minus 370 degrees Fahrenheit or minus 223 degrees Celsius. Internal radiators cool some of the telescope's sensors even colder.
Engineers found seven cracks on the sunshield membranes in a previous deployment test, and a tension system that holds the diaphragm in shape has become too loose during the test. NASA is at risk of getting caught.
Ever since the ground crews discovered and repaired the cracks in the sunshade, they've subjected the element of the spacecraft holding the sunshade to a series of vibration, acoustic, and thermal vacuum tests to expose the hardware to shaky, loud noise, airless environments that it encounters at takeoff and in space.
"They will now use the sunscreen to make sure it behaves as expected after launch (environments)," Smith said Wednesday. "They let go of all the membrane devices and push out the cantilevers for the sunshade and pull up the membranes.
" That's one of the things they're sure to look for is to have gone through the environments like the mold is from the sunscreen that comes out of these? "Smith said. "Were the procedures you introduced to correct some of the things that caused some tears last time, did they work as planned? This is an essential part of this on-call test.
"They also had to make some adjustments to the so-called diaphragm tensioning system, the system of pulleys that actually tightens the sunshield," Smith said in an interview with Spaceflight Now. "So they made those adjustments and we'll see that we did exactly what we needed them to do."
Northrop Grumman's test crew will also deploy other structures on the telescope and then pass the entire observatory through electrical, vibration and acoustic tests. After these checks are completed, technicians re-deploy the entire observatory to ensure that all mechanisms have passed the testing of the launch environment.
Then the technicians stow the observatory in the launch configuration.
The observatory can be folded in origami style Fits under the payload fairing of the Ariane 5 rocket. Depending on how you count, Webb will have more than 300 deployments after it has been disconnected from the top tier of the Ariane 5 launcher. Similarly, according to NASA, the Curiosity Mars rover had about 70 stations.
The new observatory, named after James Webb, the NASA administrator from 1961 to 1968, will be stationed nearly a million miles (1.5 million kilometers) long from Earth with a 6.5-meter mirror and look into the distant universe and investigate the turbulent consequences of the Big Bang, the formation of galaxies, and the planetary environment around other stars.  For the first time, teams have linked the science and spacecraft segments of James Webb Space Telescope. Credit: NASA / Chris Gunn
Smith said that NASA has about three months' leeway before the planned launch of the mission on March 30, 2021. This extra time could be used to solve problems that occur during the remaining soil tests.
"They're testing this hardware on-site, because if there's a problem, you want to find it so you can fix it before you put it into orbit," Smith said. "A program as big as Webb has a very extensive test program, and we still have to work that through.
I do not understand that (completely) as we have already done – these numbers are getting smaller now, "he said. "Most of this hardware has already been tested. The vibration test and the acoustic test form one unit, yes, this is a first time activity since we never had them together. But it's something we have to do, and that's why we've included a margin plan to fix problems that go wrong during testing, if that's the case. "
NASA has acknowledged last year that Webb would not be ready for the previous target launch date in 2019. This startup delay occurred after the announcement in 2017 that the mission would not start as planned in 2018.
The start-up delay until 2021 was associated with an additional cost of nearly $ 1 billion. It was just the latest in a series of budget busting plans in the history of the program.
An independent review panel attributed the recent delay and cost growth mainly to errors made by the Webb manufacturing and testing team at Northrop Grumman. The panel also said that NASA is too optimistic about its planning predictions.
According to NASA, engineers have replaced a catalyst bed heater and valves in Webb's drive system, which have been damaged by human error.
Workers have improperly attached fasteners prior to an audible warning to Webb's sunshade test, and a series of bolts, washers and nuts detached during the spacecraft's acoustic test. With not all fasteners initially taken into account – which led to concerns that some of them got into the spacecraft – the teams have now found all the hardware, Smith said.
Read more details on the issues that caused Webb's startup delay to 2021.
Engineers have identified several other problems in the spacecraft bus that require special attention.
"When we completed the environmental tests on the spacecraft, there were two electronic components that did not work as planned." he said. "One was part of a communication system. It is an amplifier. We have redundant amplifiers, but one of them did not work as planned.
"And some boards on one of the command and telemetry processors that behaved like they did not expect," he said. So we're buying new amplifiers … and taking technical units of the command and telemetry processors we already have and setting them up for the flight.
The workers will replace the amplifier and command and telemetry processor after using the sun visor test.
"At the same time we're swapping out this amp, we're going to swap one of these command and telemetry processors, which is a redundant system, so we just replace one of them."
"The spaceship has all its electronics and avionics on the side panels, so there's a time when we basically have to flatten one of those panels to replace these two things," Smith said. So we had to spend a certain amount of time to match modify that change, but that's taken into account, and we still have a head start before the start.
ESA and Arianespace officials have also agreed to modify the design of the vents on the payload fairing of the Ariane 5 rocket to address the issue of pressure relief could damage the Webb observatory if the fairing after takeoff is dropped.
The cup-shaped fairing protects Webb, while the Ariane 5 rocket fires through the dense lower layers of the atmosphere. Once the disguise is above the recognizable atmosphere, it detaches and loses weight as the Ariane 5 ascends into space.
Engineers were concerned that residual air trapped in Webb's folded sunshield membranes could cause a "congestion" condition at the time the panel was disconnected.
Smith said NASA's Ariane 5 carrier Arianespace equipped with high-fidelity sensors to fly on two Ariane 5 missions and measure the pressure inside the fairing during disguise disassembly.
A problem with the pressure relief, which means that there would be enough residual pressure that could endanger some of our hardware, "said Smith. "So they agreed that they needed to install extra hardware on their louvers to fix this problem.These shrouds have vents on the floor, and we believe the problem was that they were on their way up open just because they vibrate around, may not stay fully open.
"So ESA and Ariane are working on a design that essentially keeps these vents open once they're open, and all calculations show that the pressure is dropping there should be where we need it for our payload, "Smith said," for this story to come to a good solution. "
The new hardware that leaves the vents open will fly in front of Webb in an Ariane 5 mission, to check the changes.
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