A new report on the James Webb Space Telescope has found that ongoing technical issues with final testing and assembly of the $8.8 billion project will probably cause the launch date of the oft-delayed instrument to slip again to the right. Presently, NASA is targeting June 2019 for launch aboard an Ariane 5 rocket.
The US Government Accountability Office published the report on Wednesday. It concluded, "Given several ongoing technical issues, and the work remaining to test the spacecraft element and complete integration of the telescope and spacecraft, combined with continuing slower-than-planned work at Northrop Grumman, we believe that the rescheduled launch window is likely unachievable."
The report catalogs a number of issues that Northrop Grumman has dealt with during the integration process, particularly the technical challenges and workforce issues needed to meet them. For example, the report cites a worrying problem that cropped up during one of the tests to deploy the telescope's essential sunshield—one of its six membrane tensioning systems experienced a potentially crippling "snag."
Moreover, last year the contractor found that eight of 16 valves in the spacecraft's thrusters were leaking beyond acceptable levels. Although it could not conclusively determine the cause of the leak, Northrop Grumman ultimately determined that this was most likely caused by technician handling errors. The thruster modules had to be individually investigated, refurbished, and re-attached, which contributed months of delays to the schedule.
All of this has left the telescope project with just 1.5 months of schedule reserve. In recognition of this urgency, Northrop Grumman has, according to the report, increased its daily work shifts from two to three, and teams are now working 24 hours per day on spacecraft integration.
This 24-hour-a-day work means that it will not be possible for Northrop Grumman to pour more people into the telescope should further technical issues arise, which the GAO report suggests is likely due to the nature of such a complex project. Moreover, Northrop Grumman had intended to begin to scale back its workforce last year, but due to the problems, it has yet to significantly cut back.
As a result, the James Webb Space Telescope is now perilously short on schedule margin, and with further delays likely and contractor workforce costs still high, it may very well exceed its Congressionally mandated cost cap. The telescope's managing board will soon meet, the report says, and will determine whether the June 2019 launch date can still be met.
Engineers removed the combined optics and science instruments of NASA’s James Webb Space Telescope from their shipping container in a high bay at Northrop Grumman Aerospace Systems in Redondo Beach, California, on March 8, signaling the next step in the observatory’s integration and testing.
Northrop is the final step of Webb’s journey before it travels to its launch site in Kourou, French Guiana. Engineers will conduct final testing at the facility to ensure the observatory is ready for space. Webb’s combined optics and science instruments, the science payload, is the half of the observatory that includes Webb’s iconic, 6.5-meter (21.3-foot), golden primary mirror. The science payload recently arrived at Northrop after testing at NASA’s Johnson Space Center in Houston.
The integrated spacecraft and sunshield — the other half of the observatory, which is in final assembly at Northrop — will soon undergo its own launch environment tests to prove it is ready to be combined with the science payload. Then, additional testing will be performed to guarantee the fully assembled observatory will successfully operate in its orbit at the second Sun-Earth Lagrange point (L2).
The science payload was already separately proven to be able to withstand the rigors of launch and operate as expected at cryogenic temperatures through tests last year at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and at Johnson. Making sure every element of Webb functions correctly before it gets to space is critical, because at that orbit it will be beyond the reach of any servicing missions.
“Extensive and rigorous testing prior to launch has proven effective in ensuring that NASA’s missions achieve their goals in space,” said Eric Smith, program director for Webb at NASA Headquarters in Washington, D.C. “Webb is far along into its testing phase and has seen great success with the telescope and science instruments, which will deliver the spectacular results we anticipate.”
These final tests at Northrop are critical to making sure the fully assembled observatory deploys and operates as expected in space. Deployment is the most critical part of Webb’s journey to L2. To reach space, the telescope must fold origami-style inside its Ariane 5 rocket for launch. Once in space and detached from the rocket’s payload adaptor, Webb will unfold its sunshield and deploy its mirrors, including its highly complex primary mirror. It will be the first space telescope to complete such an intricate process.
Opening Webb’s tennis court-sized, five-layered sunshield is one of the most technically challenging parts of deployment. The sunshield must delicately fold around the telescope for launch and then carefully open in space. Opening the sunshield requires that about 100 actuators, tiny motors that control the delicate motions of deployment, correctly fire. The sunshield must deploy successfully to ensure the mirrors and science instruments of Webb stay cold enough to be able to detect the extremely faint light of far-away planets, stars and galaxies.
“Test, test and retest”
Meticulous testing ensures Webb’s success. Webb has presented novel challenges, requiring innovative solutions from the multidisciplinary teams of engineers and scientists who have contributed to the international endeavor.
Webb is the largest international space science project in U.S. history and one of the highest priority science projects within NASA. The most complex and largest space telescope ever built, Webb will answer some of the most fundamental questions we have about the origins of the universe. Webb’s many intricate systems are more complex than those of most spacecraft, and so the telescope requires thorough testing on the ground to ensure it will operate as expected in space and be able to fulfill its science mission far from Earth.
Building a complex observatory that is designed to deploy and operate in space presents several challenges. Webb’s optics and science instruments will operate at cryogenic temperatures in space, but they had to be built at room temperature on Earth. Webb’s mirrors had to be precisely polished and formed so they will achieve the correct shape when they cool in space. The sunshield will deploy in a zero gravity environment, but all deployment tests on Earth must contend with our planet’s gravity.
“At NASA, we do the seemingly impossible every day, and it's our job to do the hardest things humankind can think of for space exploration,” said Smith. “The way we achieve success is to test, test and retest, so we understand the complex systems and verify they will work.”
NASA’s James Webb Space Telescope is the world’s premier infrared space observatory of the next decade. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA).
REDONDO BEACH, Calif. – March 12, 2018 – All the major elements of NASA’s James Webb Space Telescope now reside in a giant clean room at Northrop Grumman Corporation’s (NYSE: NOC) Redondo Beach facility, setting the stage for final assembly and testing of the giant space telescope that will explore the origins of the universe and search for life beyond our solar system.
The optical telescope and integrated science instrument module (OTIS) arrived at Northrop Grumman in February. It was previously at NASA’s Johnson Space Center in Houston, where it successfully completed cryogenic testing.
OTIS and the spacecraft element, which is Webb’s combined sunshield and spacecraft bus, now both call Northrop Grumman home. Webb is scheduled to launch from Kourou, French Guiana in 2019.
The James Webb Space Telescope is the world’s premier space observatory of the next decade. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, the European Space Agency and the Canadian Space Agency.
Quelle: NORTHROP GRUMMAN