Teams working at the Northrop Grumman spacecraft in southern California are first connecting the space and science modules of the James Web Space Telescope, which is a major point when engineers prepare to check for repair tears in the solar panel of the observatory and begin to release vibrations and acoustic tests in the coming months.
Technicians at the Northrop Grumman facility in Redondo Beach, California, mated the JWST telescope with their spacecraft on August 23. Since then, workers have completed mechanical and electrical connections between the two major elements of the observatory, the most capable space telescope ever built.
"It's a huge milestone for us," says Eric Smith, a program scientist at JWST at NASA's Washington headquarters. "It's a program that was first introduced to people's minds about 30 years ago. Some of the original contracts came out in 2001 and 2002, and seeing it in this clean room is breathtaking now. Many people have been waiting a long time for this. Great to see. "
For deployment by French Guiana aboard a European Ariane 5 rocket in March 2021, the James Web Space Telescope will cost more than $ 10 billion by the time it completes its mission, including NASA's contributions to the European Space agency and the Canadian Space Agency.
NASA bears most of the cost of about $ 9.7 billion. ESA provided hardware for Webb instrumentation and launch vehicles, and Canada built a fine-tuning sensor and spectrograph for the observatory.
"It's an exciting time to see all the Webb parts finally united in an observatory for the first time," said Gregory Robinson, Web program director at NASA Headquarters. "The engineering team has taken a huge step forward, and we will soon be able to see incredible new views of our incredible universe."
Webb's space and science modules have been individually tested at various stages of assembly over the last decade. Now is the time to test the whole observatory as a whole.
Crane raised the telescopic element of the Web over the spacecraft bar and sunscreen and carefully lowered it into place. There are six mechanical anchorage points between the science module, which include the telescope and Web science tools, and the spacecraft bus, plus about a dozen wires, each carrying numerous data and electrical cables, says Smith
. , they will deploy an observatory tennis court on the Observatory's tennis court, a thermal barrier designed to keep Web's sensitive infrared detectors cold.
Made of five Capton membranes, each as thin as human hair, the sunscreen is designed to be positioned in 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 Web instruments as cold as minus 370 degrees Fahrenheit or minus 223 degrees Celsius. Internal coolers will cool some of the telescope's sensors even colder.
Engineers found seven membrane ruptures on a solar screen during a previous deployment test, and a tension system used to keep the membrane in its shape developed too much during the test, creating a risk of clogging, NASA said.
Ever since the sun's protective tears have been discovered and repaired, ground-based crews have placed the spacecraft element holding the sunscreen, through a series of vibration tests, acoustic and thermal vacuum, to expose the hardware to shaking, noisy, noisy, cold which collides during launch and into space.
"They will now deploy the sunscreen to make sure it behaves as expected after passing through the launches," Smith said Wednesday. "They will release all the membrane devices and push the sunscreen arrows and stretch the membranes.
"This is one of the things they will surely be looking for, having gone through the environment, what is the shape of the sunscreen coming out of them? said Smith. "Did the procedures they put in place to correct some of the things that caused the tears last time work as planned? This is very much a part of this deployment test.
"They also had to make some adjustments to the so-called membrane tensioning system, the washer system that actually tightens the solar screen," Smith said in an interview with Spaceflight Now, "So they made these adjustments and we'll see that they did
The test crew at Northrop Grumman will deploy other structures of the telescope and then place the entire observatory through electrical, vibration and acoustic tests. Once these checks are completed, technicians will deploy the full observatory once more to make sure that all mechanisms have survived the test of the launch medium.
Then the technicians will bring the observatory into configuration at launch.
The origami style folding observatory is placed under the hood of the Ariane 5 rocket. Depending on how you count, Webb will have more than 300 deployments after separating from the upper stage of the Ariane 5. Launcher. similarly, the Curiosity Mars rover had about 70 locations, according to NASA.
Named for James Webb, NASA Administrator from 1961 to 1968, the new observatory will be located nearly one million miles (1.5 million kilometers) from Earth using a 21.3-foot (6.5-meter) mirror and four scientific tools to peer into the distant universe, studying the stormy aftermath of the Big Bang, the formation of galaxies, and the planets of planets around other stars.  Teams for the first time link the James Webb Space Telescope science and space ships. Credit: NASA / Chris Gan
Smith said NASA has about a three-month margin on the Web schedule before the mission's launch date of March 30, 2021. This extra time can be used to resolve issues that arise during the remaining ground tests.
"You're testing this hardware on earth because if there are problems, you want to find them so you can fix them before you send them into orbit," Smith said. "A program as big as the Web has a very extensive testing program, and this is something we have to go through.
"The number of activities for the first time – those things we've never done before, and therefore maybe" I don't understand (completely) as something we've done before – those numbers are already getting small, "he said. "Most of this hardware is used. Vibration and the acoustic test as a whole, yes, this is an initial activity, because we have never done it together before. But this is something we will have to do, and so we have a built-in graph margin to fix things that would go wrong if they did, during testing. "
NASA last year acknowledged that the Web would not be ready for its previous goal Release Date in 2019. This launch delay came after the announcement in 2017 that the mission would not start in 2018, as it was planned earlier.
The delay in launching to 2021 came at an additional cost of nearly $ 1 billion. It was the latest in a series of budget scams written in the program's torture history.
An Independent Review Board blames the latest cost delays and increases, mainly on the mistakes of Webb's Northrop Grumman production and test team.
NASA claims that engineers have replaced the catalyst heater and valves in the Web's propulsion system, damaged by human error.
Workers improperly installed fasteners on the Web's solar screen before an acoustic test system and a number of screws, washers, and nuts were released during the spacecraft's acoustic test. After initially failing to account for all of the fasteners – raised by concerns that some of them hit the spacecraft, the teams found all the hardware, Smith said.
Read more details on issues that have delayed Webb's launch by 2021.
Engineers have identified several other spacecraft bus problems that require attention, Smith said.
"When we came out of the spacecraft environmental tests, there were two electronic components that did not work as planned," he said. "One was a component of a communication system. It is an amplifier We have redundant amplifiers, but one of them does not work as planned.
"And some boards on one of the command and telemetry processors that (also behaved in a way that wasn't expected," he said. So we buy new amplifiers … and we take the engineering units of the command and telemetry, which we already have, and improving those for flight. "
Workers will replace the amplifier and control and telemetry processor after the sunscreen has been deployed. command and telemetry processors, "Smith said. It's a redundant system, so we're just replacing one of them. "
" The spacecraft has all its electronics and avionics on the side panels of it, so now there's a period where we have to basically (put) one of those panels flat to replace those two things, "Smith said. So we had to use some stock on schedule to motivate this change, but that was taken into account and we still have the stock to run. "
ESA and Arianespace officials also agreed to modify the design of the Ariane 5 rocket payload vents to address concerns that a pressure-down event could damage the Web Observatory when drainage flows after expiration.
The rolling fairing will protect the Web like Ariane 5 rockets through the dense lower layers of the atmosphere. Once the atmosphere has been exceeded, the fairing will release to its brunt when Ariane 5. ascends into space.
Engineers were concerned about the residual air trapped in Webb's folded solar membranes could cause "over-voltage" at the time of the fairing's separation.
Smith said NASA provided Arianespace, the Ariane 5 startup operator, with high-precision sensors to fly two Ariane 5 missions and measure pressure inside the fairing during the roof separation sequence.
"They show that there is a problem with lowering the pressure, which means that there will be enough residual pressure that can endanger some of our hardware," Smith said. "So they agreed that to resolve this, what they are going to do is install extra hardware on their openings. These covers have openings around their base and we believe the problem was that as they open on the way up, just because they vibrate around, they may not remain fully open all the way.
"So ESA and Ariane are working on a design that essentially it will hold these openings once they open, and all calculations indicate that this should cause the pressure to drop below where we need it for our payload, "Smith said." So this story goes well resolution. "
The new hardware for keeping the openings open will fly into the Ariane 5 mission before Webb checks the change.
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