An Angara A5 rocket lifts off Dec. 27 from the Plesetsk Cosmodrome. Credit: Russian Ministry of Defense
The third test launch of Russia’s heavy-lift Angara A5 rocket Dec. 27 was marred by an upper stage failure that stranded a dummy payload in a low orbit.
The Angara A5 rocket launched from the Plesetsk Cosmodrome, located in Russia’s Arkhangelsk region about 500 miles (800 kilometers) north of Moscow, at 2 p.m. EST (1900 GMT) on Dec. 27, according to Russia’s Ministry of Defense.
Liftoff occurred at 10 p.m. Moscow time to begin the third test flight of Russia’s heavy-lift Angara A5 rocket, following successful demonstration launches in 2014 and 2020.
The rocket’s five RD-191 engines collectively generated more than 2 million pounds of thrust to power the Angara A5 off the launch pad at Plesetsk.
Heading downrange east of Plesetsk, the rocket surpassed the speed of sound and jettisoned its four strap-on booster engines nearly three-and-a-half minutes into the flight. Then the rocket’s core stage, which fired its RD-191 engine at a lower throttle setting in the early phase of flight, powered up to full throttle to continue climbing into space.
The core stage switched off its engine and dropped away from the Angara’s third stage nearly five-and-a-half minutes after liftoff. A kerosene-fueled RD-0124 engine ignited on the third stage and fired for nearly seven minutes.
The Angara’s payload fairing jettisoned early in the third stage burn, revealing the rocket’s dummy payload after climbing into space.
The rocket then deployed a Persei, or Perseus, upper stage to perform a series of engine burns to maneuver into an orbit near geostationary altitude more than 22,000 miles (nearly 36,000 kilometers) above Earth.
A first burn was expected to accelerate the Persei stage into a parking orbit. That engine firing apparently concluded as planned.
But the upper stage did not conduct the additional engine burns needed to climb into a higher orbit. U.S. military tracking data showed the Persei upper stage, with its satellite mock-up payload presumably still attached, in a low orbit between 110 miles and 124 miles (177-by-200 kilometers) in altitude, well short of the mission’s target.
The orbit’s track was tilted at an angle of 63.4 degrees to the equator, according to radar tracking information obtained and published by the U.S. military.
The Russian Ministry of Defense confirmed the Angara A5 rocket’s blastoff from Plesetsk, but Russian officials provided no additional updates on the progress of the Persei upper stage.
The Persei stage is a modified version of the Block DM upper stage used on more than 200 Russian launches since 1974. The Angara A5 test flight Dec. 27 was the first use of the new Persei upper stage variant.
The first two Angara A5 test flights used Breeze M upper stages to place dummy payloads close to geostationary orbit. The Persei upper stage uses a different propellant mix — kerosene and liquid oxygen — than the hydrazine-fueled Breeze M.
The impact of the Persei stage failure on the Angara program was not immediately clear. But the Angara A5’s boosters, core stage, and second stage all apparently functioned as designed Dec. 27, giving the roc
The expendable Angara rocket family is designed to fly in several different configurations, depending on the mass of its payload and the targeted orbit.
The Angara A5 can place up to 24.5 metric tons — about 54,000 pounds — into a 120-mile-high (200-kilometer) orbit. On missions with communications satellites heading for geostationary transfer orbit, an Angara A5 rocket can lift up to 5.4 metric tons, or about 11,900 pounds, according to Khrunichev State Research and Production Space Center, the Angara’s prime contractor.
The Russian government gave the green light for development of the Angara rocket in 1992. After Khrunichev won the contract to design and build Angara, the Russian government stated the rocket should begin operations by 2005.
But funding difficulties repeatedly delayed the Angara program. Finally, in 2014, Russia performed the first two Angara test flights.
A single-core prototype of the light-class Angara 1.2 rocket — designed to loft smaller satellites — flew on a suborbital test flight in July 2014. The Angara A5 rocket debuted in December 2014, also successfully.
At that time, Russian officials said multiple Angara test flights were scheduled before the rocket was to become operational in 2020.
Russia did not meet that schedule. Since 2014, officials have opened a new Angara production facility in Omsk, Russia.
The Angara burns cleaner fuel than the Proton rocket it will replace, which consumes toxic hydrazine and nitrogen tetroxide propellants.
Russian workers are building a new Angara launch pad at the Vostochny Cosmodrome in Russia’s Far East. Roscosmos, Russia’s space agency, said Dec. 27 that the launch pad at Vostochny will be completed next year, in time to host the first Angara launch there in 2023.
Russia’s medium-lift Soyuz rocket has launched from Vostochny, Russia’s newest spaceport, since 2016.
Once operational, the Angara A5 rocket will allow Russia to move some of its space launches from the Baikonur Cosmodrome, which the Russian government leases from Kazakhstan, to spaceports on Russian territory.
Artist’s concept of the James Webb Space Telescope with one half of its sunshield deployed. Credit: NASA
Flying outbound from Earth at a distance of more than 400,000 miles, the James Webb Space Telescope extended one of two booms Friday to begin unfurling the mission’s five-layer sunshield. With the port-side boom deployed, work is underway tonight to extend another boom on the starboard side.
The critical deployments mark some of the most nail-biting moments to ready the nearly $10 billion observatory for science operations, following its successful launch Dec. 25 aboard a European Ariane 5 rocket.
NASA confirmed the successful extension of the port-side mid-boom in an update shortly after 7 p.m. EST Friday (0000 GMT Saturday).
Ground teams started extending the two sunshield booms several hours later than originally scheduled, NASA said in an update Friday evening. The space agency said mission controllers at the Space Telescope Science Institute took extra steps to confirm that a sunshield cover had fully rolled up before proceeding with the first mid-boom deployment.
“Switches that should have indicated that the cover rolled up did not trigger when they were supposed to,” NASA said. “However, secondary and tertiary sources offered confirmation that it had. Temperature data seemed to show that the sunshield cover unrolled to block sunlight from a sensor, and gyroscope sensors indicated motion consistent with the sunshield cover release devices being activated.”
The covers were opened and rolled back to expose the sunshield to space Thursday.
Five telescoping segments fo the port, or left-side, mid-boom began extending around 1:30 p.m. EST (1830 GMT) Friday. The motor-driven boom reached full deployment at 4:49 p.m. EST (2149 GMT), NASA said.
Officials have repeatedly said Webb’s deployment schedule could change based on real-time conditions. Friday’s activities showed the ground team’s flexibility.
Managers decided Friday evening to move forward with extending the starboard mid-boom, and initial steps for that deployment began shortly after 7 p.m. EST (0000 GMT), NASA said.
JWST’s sunshield deployment during a ground test at Northrop Grumman. Credit: NASA
The James Webb Space Telescope opened covers that protected the mission’s folded sunshield Thursday, and deployed a momentum flap to help the observatory balance against the unending light pressure from the sun.
The steps pave the way for a critical three days of work to open the sunshield and tension all five of its ultra-thin layers, made of kapton with aluminum and silicon coatings.
The sunshield covers released Thursday after ground teams at the Space Telescope Science Institute uplinked commands to Webb, on its way to an operational orbit around the L2 Lagrange point nearly a million miles (1.5 million kilometers) from Earth.
“Webb’s engineers have released and rolled up the sunshield covers that protected the thin layers of Webb’s sunshield during launch,” NASA said in an update Thursday. “After the team electrically activated release devices to release the covers, they executed commands to roll the covers up into a holding position, exposing Webb’s sunshield membranes to space for the first time.”
The five membranes were folded and stowed for launch to fit inside the nearly 18-foot (5.4-meter) diameter of the payload fairing on the European Ariane 5 rocket, which hurled Webb into space on Christmas Day.
Mission controllers confirmed the covers were released at 12:27 p.m. EST (1727 GMT) Thursday.
Earlier in the day, Webb deployed a momentum tab on the back side of the observatory. The eight-minute process involved releasing the flap’s hold-down devices, then a spring moved the flag into its final position, according to NASA.
The flap will help keep Webb stable against the bombardment of solar photons, or light energy, from the sun throughout the observatory’s astronomy mission. The mission’s giant sunshield, once deployed, will catch the solar photons like a kite moves with the wind, but with more subtle effects.
Without the aft momentum flag, the influence of the sun would require Webb’s six reaction wheels to counteract the movement to keep the telescope properly pointed. In turn, Webb would need to fire its thrusters and consume fuel more often to offload momentum from the reaction wheels.
The deployments Thursday followed the unfolding of the sunshield pallets containing Webb’s thermal barrier Tuesday. On Wednesday, Webb extended a telescoping tower holding the mission’s primary mirror segments and science instruments, creating some distance between the hardware, which must be cooled to cryogenic conditions, and the relatively warm spacecraft, with its solar array pointed at the sun.
That clears the way for critical work, set to begin Friday, to open the sunshield to its full dimension, roughly the size of a tennis court.
Made of five fragile kapton membranes, each as thin as a human hair, the sunshield will keep Webb’s mirrors, instruments, and detectors in constant shadow, allowing their operating temperature to plummet to near minus 400 degrees Fahrenheit. Such cold conditions are required to allow Webb to see the faint infrared light from the first galaxies in the universe more than 13.5 billion light years away.
Most NASA managers and astronomers waiting to use the nearly $10 billion Webb telescope give the same answer about the most stressful moment of the mission: Sunshield deployment.
“The sunshield is one of these things that is almost inherently indeterministic,” said Mike Menzel, Webb’s mission systems engineer at NASA’s Goddard Space Flight Center in Maryland. “NASA is used to deploying rigid beams on hinges, because they’re deterministic, you can determine how they move.”
“Given that there are 40 different major deployments, and hundreds of pulleys and wires, the whole thing makes me nervous and will until its fully deployed,” said John Grunsfeld, an astrophysicist, former astronaut, and head of NASA’s science mission directorate from 2012 until 2016, a key period in Webb’s development.
But it’s the sunshield that got the biggest share of Menzel’s attention during the design and testing of Webb.
Menzel compares predicting the behavior of the sunshield layers to guessing what a string will do when you push it on a table top.
“So it is with the membranes of the sunshield,” he said. “So we can’t really predict their shape, but we can constrain it. “We can try to prevent it from going in places that we don’t want it to go, places where it could snag or tear, or maybe impede the deployment of other members.”
Two booms will extend from each side of Webb as soon as Friday. With the assistance of deployment motors, the structural support booms will pull the five sunshade membranes out into their distinctive diamond shape.
It all happens slowly, with sensors across the observatory tracking how the sunshield opens. Ground controllers can pause in between steps to ensure everything is working as designed.
Each layer of the sunshield is slightly different in size and shape, created using thermally bonded sections of kapton with around 10,000 seams, according to Krystal Puga, Webb’s lead spacecraft systems engineer at Northrop Grumman.
There are reinforcement strips, or rip stops, to contain any tears or holes, and metallic ribbons giving the kapton some structural support.
The sunshield membranes are coated with aluminum, and two of the outermost layers are treated with silicon, giving the skin-like material a purple hue.
Webb has 344 devices that must work exactly as intended. Of those, 107 are membrane release devices, non-explosive actuators that pin the sunshield in place for launch.
In total, the mission’s deployment sequence relies on 140 release mechanisms, 70 hinge assemblies, eight deployment motors, 400 pulleys, and 90 cables running a quarter-mile in length. There are also an array of bearings, springs, and gears to transform Webb from its launch to operational configuration.
With the sunshield in its diamond shape, covering an area the size of a tennis court, Webb controllers will send commands for the observatory to tension each of the five layers over two days — currently planned on Saturday and Sunday.
“Once we get the sunshield out, that’s great, but then we have to sort of tighten it up,” said Keith Parrish, NASA’s commissioning manager for Webb, in an interview before launch. “All five layers have different points around them where they’re connected up, and then we’ll pull on cables in each one of those corners to actually tighten up the sunshield.”
“The very last step is super important,” Puga said. “We need to tension all of the membranes using a series of pulleys and cables to create the separation between each of the five layers.”
The tensioning will separate each of the five ultra-thin kapton membranes, spacing them a few inches at the center and a few feet at the outermost edges. The tapered spacing helps allow heat from the sun to reflect between the layers, and eventually radiate back into space.
A Soyuz-2.1b rocket lifts off Dec. 27 with 36 OneWeb satellites. Credit: Roscosmos
A Russian Soyuz rocket launched Monday with 36 more OneWeb internet satellites, the 12th of 19 Soyuz missions needed to deliver into orbit the company’s first-generation network of nearly 650 spacecraft.
The mission took off from the Baikonur Cosmodrome in Kazakhstan at 8:10:37 a.m. EST (1310:37 GMT), or 6:10 p.m. local time at the historic cosmodrome in Central Asia, about one hour after sunset.
Thirty-six OneWeb satellites, built in Florida, were mounted top of the rocket as it fired away from Baikonur with nearly a million pounds of thrust. Arcing to the north from Baikonur, the 15-story launcher jettisoned its four kerosene-fueled boosters about two minutes after liftoff, then released its core stage and payload fairing.
A third stage engine finished the Soyuz rocket’s role in the mission less than 10 minutes into the flight, giving way to a Fregat upper stage for a pair of orbit insertion burns to reach a polar orbit around 279 miles (450 kilometers) high.
The satellites separated from the dispenser in groups of four, beginning about 1 hour, and 18 minutes, after launch. The final four satellites deployed nearly four hours into the mission.
The satellites were expected to unfurl solar panels and use their ion thrusters to reach an operational orbit at 745 (1,200 kilometers) miles above Earth.
“Today’s launch is a great way for OneWeb to complete a highly successful year,” said Neil Masterson, CEO of London-based OneWeb. “With more than sixty percent of our constellation now in space, the business is fully-funded and we have a growing workforce of more than 400 people. I have been immensely proud to lead the business and our team over the last year as we continue to make substantial progress launching our global network, and I look forward to building on this momentum in 2022.”
OneWeb’s satellites are built in a factory just outside the gates of NASA’s Kennedy Space Center in Florida by a joint venture between OneWeb and Airbus Defense and Space.
The company’s network is one of two large mega-constellations well advanced into deployment and initial operations. SpaceX’s Starlink internet fleet is the other one.
SpaceX has launched 1,944 satellites for the Starlink network to date using the company’s reusable Falcon 9 rocket fleet. SpaceX’s Starlink satellites fly closer to Earth than OneWeb’s spacecraft — at an altitude of around 340 miles (550 kilometers) — reducing risks that failed satellites will create a long-term space junk problem. But the lower altitude means the Starlink network needs more spacecraft than OneWeb to connect the globe.
Arianespace won a contract in 2015 to launch OneWeb’s first-generation network. After several changes to the contract, the deal between Arianespace and OneWeb now covers 19 launches aboard Russian Soyuz rockets from spaceports in Russia, Kazakhstan, and French Guiana.
Monday’s launch was the 12th Soyuz launch with OneWeb satellites since the first batch rocketed into orbit in February 2019. OneWeb is planning another generation of spacecraft to handle more internet traffic, and that constellation could number thousands of satellites.
OneWeb has launched 394 satellites, with the new craft shot into orbit Monday. The company plans to deploy 648 satellites in its first-generation constellation, enough to provide low-latency internet service worldwide.
The satellites each weigh about 325 pounds (147.5 kilograms) at launch, with xenon fuel for the ion thrusters used in orbital maneuvers. For launch, the spacecraft are positioned on a custom-built dispenser structure inside the Soyuz rocket’s payload shroud.
OneWeb and Arianespace plan to complete launches of the first-generation fleet in 2022, with seven Soyuz flights scheduled from Baikonur and French Guiana. The next OneWeb launch, set for February, will originate from the French Guiana spaceport.
A Long March 7A rocket lifts off Dec. 23 from the Wenchang space center. Credit: CASC
China launched two classified Shiyan satellites Dec. 23 into a geostationary transfer orbit aboard a Long March 7A rocket, one of the country’s newest launch vehicles. The mission took off from China’s Wenchang launch base on Hainan Island.
The 199-foot-tall (60.7-meter) rocket launched from Wenchang at 5:12 a.m. EST (1012 GMT) on Dec. 23, according to the China Aerospace Science and Technology Corp., or CASC, China’s biggest state-owned aerospace contractor.
The Long March 7A lifted off powered by six kerosene-fueled YF-100 engines — two on the rocket’s core stage and four under a cluster of strap-on boosters — and headed downrange over the South China Sea. The engines generated 1.6 million pounds of thrust before the boosters and core stage shut down and jettisoned.
A second stage with four kerosene-burning YF-115 engines fired next, then gave way to a hydrogen-fed third stage with two YF-75 engines. The third stage deployed the two satellites — designated Shiyan 12-01 and Shiyan 12-02 — into an elongated geostationary transfer orbit ranging between 120 miles (200 kilometers) and 22,245 miles (35,800 kilometers) above Earth, with an inclination of 19.5 degrees to the equator.
The orbital parameters suggest the Shiyan 12 satellites will use their on-board propulsion systems to circularize their altitude at more than 22,000 miles over the equator. At that altitude, known as a geostationary orbit, the satellites will circle Earth in lock-step with the planet’s rotation.
CASC and Chinese state media said the Shiyan 12 satellites will be “mainly used for space environment detection and related technical tests.”
Shiyan means “experiment” in Chinese. Some Shiyan satellites are believed by independent experts to have a military purpose.
The launch Thursday marked the seventh flight of a Long March 7 rocket, and the third using the Long March 7A configuration.
The Long March 7 is designed to launch medium-sized satellites, such as Tianzhou resupply ships for China’s space station in low Earth orbit. The Long March 7A variant flies with a reignitable third stage, giving the rocket an ability to deploy satellites — like the Shiyan 12 pair — heading into higher orbits.
The Long March 7A rocket can carry payloads of up to 15,400 pounds, or 7 metric tons, into geostationary transfer orbit.
China debuted the Long March 7A rocket in March 2020 after two successful flights of the basic Long March 7 configuration in 2016 and 2017. But the Long March 7A failed to reach orbit and fell back to Earth a few minutes after liftoff from Wenchang.
Chinese media reported one of the Long March 7A’s booster engines shut down prematurely on the failed March 2020 flight. Chinese officials blamed the failure on a pressurization problem in the liquid oxygen inlet feeding the engine.
The launch Dec. 23 was the fourth Long March 7 flight this year, including successful second Long March 7A mission in March, and two Long March 7 launches with Tianzhou cargo freighters for China’s space station.
Artist’s illustration of Webb’s configuration as of Dec. 29, with its Deployable Tower Assembly extended. Credit: NASA
The James Webb Space Telescope extended a four-foot tower Wednesday to give the observatory’s mirrors and instruments, designed to function at cryogenic temperatures, enough separation from the hot side of the spacecraft after the mission’s sunshield deploys over the next few days.
Webb’s Deployable Tower Assembly moved the telescope’s mirrors, still folded up in their launch configuration, away from the spacecraft bus. The telescope structure contains Webb’s 18 gold-coated hexagonal primary mirror segments and four infrared instruments mounted in a carbon composite module.
In an update posted online, NASA said the motor-driven telescoping tower extended about 48 inches (1.22 meters). The deployment took more than six-and-a-half hours, beginning at around 9:45 a.m. EST (1445 GMT) and ending at approximately 4:24 p.m. EST (2124 GMT), according to NASA.
Ground teams at the Space Telescope Science Institute in Baltimore, Maryland, methodically sent commands to Webb throughout the day. The human-in-the-loop control plan allows engineers to track each step of Webb’s critical deployments, from launch through commissioning and instrument calibration, culminating in the first science observations around six months into the mission.
But the mechanisms on Webb are robotic and outside the reach of engineers on Earth, or astronaut servicing. There are 344 critical devices that must function as intended for Webb to accomplish its mission observing the universe.
Webb is the largest space telescope in history, 100 times more powerful than the Hubble Space Telescope. Its primary mirror will span 21.3 feet, or 6.5 meters, in diameter once fully deployed. Hubble’s monolithic primary mirror has a diameter of 7.9 feet, or 2.4 meters.
The Deployable Tower Assembly provides separation between the telescope and the spacecraft. Webb’s sunshield, which will unfurl to the size of a tennis court, will put the telescope’s mirrors and instruments in permanent shadow, allowing them to cool down nearly minus 400 degrees Fahrenheit.
Webb’s detectors need to be cold to sense the faint infrared light emitted from galaxies more than 13.5 billion years ago, within 100 million to 200 million years after the Big Bang. The mission will also study the atmospheres of planets around other stars, and reveal new insights into our own solar system.
Webb’s spacecraft bus, which must point its solar array toward the sun to generate electricity, will see temperatures of nearly 200 degrees Fahrenheit.
The sunshield enables Webb to achieve the nearly 600-degree temperature differential, and the tower extension Wednesday also helped clear the way for the observatory to start unfolding the five-layer thermal barrier in the next few days.
“All of the material for the sunshield is actually stowed in that area, or some of it is, so we need to get the telescope up away, so that will allow us to pull that material out,” said Keith Parrish, NASA’s commissioning manager for Webb, in an interview before the mission’s Christmas Day launch.
Since launch on a European Ariane 5 rocket, Webb has extended its solar panel, completed two mid-course correction burns, unfurled its high-gain antenna, and unfolded two pallet structures Tuesday containing the ultra-thin sunshield material.
The next big event, tentatively set for Thursday, will be the opening of protective covers over the sunshield membranes. The five layers, each made of an insulating material known as kapton, took a month to carefully, and manually, stow inside the pallets, akin to the way a parachute is packed before a skydive.
An aft momentum flag will also deploy Thursday to help balance Webb against the tenuous, but constant, bombardment by pressure from sunlight. Photons zipping by Webb at the speed of light will push against the sunshield, and the rear flap will help stabilize the observatory and minimize fuel usage to counteract the pressure.
As soon as Friday, mission control will uplink commands for Webb to extend two booms from each side of the spacecraft. The booms will help pull the sunshield layers into their distinctive kite-like diamond shape.
A system of cables and pulleys will tension each of the five layers this weekend, creating space between each membrane to help radiate heat from the sun back into space. The sunshield deployment is widely cited by astronomers and engineers as the riskiest moment in the life of the nearly $10 billion Webb telescope.
Then engineers will move on to position Webb’s secondary mirror and the telescope’s port and starboard mirror wings into place on each side of the fixed central mount. The wings each hold three of Webb’s 18 primary mirror segments, while 12 segments are on the center section.
Artist’s illustration of the Webb telescope’s sunshield pallet opening. Credit: NASA
Mission controllers started the risky process Tuesday to unfurl the James Webb Space Telescope’s sunshield, a five-layer thermal barrier necessary to give the observatory infrared vision into the distant universe.
Two large pallets containing the sunshield membranes were folded up on each side of Webb’s primary mirror for launch. Now, with Webb on course toward an observing post nearly a million miles (1.5 million kilometers) from Earth, ground teams are ready to open up the sunshield to its full dimension.
Made of five fragile kapton membranes, each as thin as a human hair, the sunshield will keep Webb’s mirrors, instruments, and detectors in constant shadow, allowing their operating temperature to reach near minus 400 degrees Fahrenheit. Such cold conditions are required to allow Webb to see the faint infrared light from the first galaxies in the universe more than 13.5 billion light years away.
Webb, the largest space telescope ever launched. had to fold up to fit inside the payload fairing of its Ariane 5 rocket for liftoff Christmas morning.
“We built a world-class infrared telescope,” said Mike Menzel, Webb’s mission systems engineer at NASA’s Goddard Space Flight Center. “We built it, we’ve aligned it, we’ve tested it, and proved it worked.”
“Now, we’re going t have to break it up, fold it up, and actually rebuild it on orbit — rebuild it, realign it, retune it and get it to work robotically on orbit. That’s never been done before.”
Most NASA managers and astronomers waiting to use the nearly $10 billion Webb telescope give the same answer about the most stressful moment of the mission: Sunshield deployment.
“The sunshield is one of these things that is almost inherently indeterministic,” Menzel said. “NASA is used to deploying rigid beams on hinges, because they’re deterministic, you can determine how they move.”
Once the sunshield is opened to its full size — with the approximate dimensions of a tennis court — NASA will send commands to open wings on each side of the telescope’s primary mirror, giving the aperture its final diameter of 21.3 feet (6.5 meters). A tripod-like structure with Webb’s secondary mirror must also deploy.
“Given that there are 40 different major deployments, and hundreds of pulleys and wires, the whole thing makes me nervous and will until its fully deployed,” said John Grunsfeld, an astrophysicist, former astronaut, and head of NASA’s science mission directorate from 2012 until 2016, a key period in Webb’s development.
But it’s the sunshield that got the biggest share of Menzel’s attention during the design and testing of Webb.
Menzel compares predicting the behavior of the sunshield layers to guessing what a string will do when you push it on a table top.
“So it is with the membranes of the sunshield,” he said. “So we can’t really predict their shape, but we can constrain it. “We can try to prevent it from going in places that we don’t want it to go, places where it could snag or tear, or maybe impede the deployment of other members.”
If everything goes according to plan, the timeline to deploy and tension the sunshield will take five days. But mission planners have flexibility in that schedule, and could decide to postpone or defer some steps to look at data in the event of a problem.
The first day of sunshield deployment apparently went off without a hitch. NASA said the two sunshield pallets lowered into position in front of and behind the telescope Tuesday. The two pallets extend 69.5 feet (21.2 meters) tip to tip.
The pallets, called Unitized Pallet Structures, contain the five kapton sunshield layers carefully folded and stowed by engineers at Northrop Grumman, NASA’s prime contractor for the Webb mission.
“Webb is beginning to resemble the form it will take when it is fully deployed – now that the mission operations team has successfully deployed and latched into place the observatory’s forward and aft Unitized Pallet Structures,” NASA said in an update late Tuesday.
The forward pallet lowered first, with its unfolding finished at around 1:21 p.m. EST (1821 GMT) Tuesday, NASA said. The next step was the unfolding of the aft pallet, which was confirmed fixed in its deployed position at around 7:27 p.m. EST (0027 GMT).
It took around 20 minutes to deploy the forward pallet, and 18 minutes to move the aft pallet, NASA said. But the process included additional steps spanning several hours, allowing ground teams to monitor structural temperatures and maneuver the observatory with respect to the sun to provide optimal thermal conditions for the deployments, the agency said.
Ground teams also turned on heaters, activated release mechanisms, and verified software configurations before latching the pallets into place, NASA said. Mission control for Webb is at the Space Telescope Science Institute in Baltimore, Maryland.
“Each deployment usually involves a bunch of motor checks, small moves to verify motor performance, heating of anything that is too cold, etc,” said Keith Parrish, Webb’s commissioning manager at NASA. “We also have to power on and configure our deployment electronics, which controls the whole show. “
The deployment of the sunshield pallets followed a smooth first three days in space for Webb.
The three-story-tall observatory launched from French Guiana on Christmas morning atop a European Ariane 5 rocket. The launcher delivered Webb to a bullseye point in space, and the spacecraft unfurled its solar array, completed two mid-course correction burns, and opened its high-gain antenna over the last few days.
Webb has passed the orbit of the moon en route to an operating orbit around the L2 Lagrange point, a gravitational balance point nearly a million miles beyond the night side of the Earth. The spacecraft is scheduled to arrive in its halo orbit around L2 in late January.
Next up is the raising of Webb’s Deployable Tower Assembly, which moves the telescope away from the spacecraft. The telescope structure contains Webb’s 18 hexagonal primary mirror segments and four infrared instruments mounted in a carbon composite module built to withstand the observatory’s cryogenic operating temperature.
That is scheduled to occur Wednesday.
“All of the material for the sunshield is actually stowed in that area, or some of it is, so we need to get the telescope up away, so that will allow us to pull that material out,” Parrish said.
The next big event, tentatively set for Thursday, will be the opening of protective covers over the sunshield membranes. The five layers took a month to carefully, and manually, stow inside the pallets, akin to the way a parachute is packed before a skydive. extension of two booms from each side of the observatory.
“It needs to be folded perfectly so that it unfolds and deploys perfectly, without snags, without any tangles,” said Krystal Puga, Webb’s lead spacecraft systems engineer at Northrop Grumman.
Launch restraints will disengage to allow the covers to roll off the top of the sunshade. Another deployment on tap Thursday, if schedules hold, is the release of Webb’s aft momentum tab, a rear flap that balances the pressure from solar light pressure on the sunshield, helping keep the observatory stable as it goes around the sun in lock-step with Earth.
Then, as soon as Friday, two booms will extend from each side of Webb. With the assistance of deployment motors, the structural support booms will pull the five sunshade membranes out into their distinctive diamond shape.
It all happens slowly, with sensors across the observatory tracking how the sunshield opens. Ground controllers can pause in between steps to ensure everything is working as designed.
Each layer of the sunshield is slightly different in size and shape, created using thermally bonded sections of kapton with around 10,000 seams, according to Puga. There are reinforcement strips, or rip stops, to contain any tears or holes, and metallic ribbons giving the kapton some structural support.
The sunshield membranes are coated with aluminum, and two of the outermost layers are treated with silicon, giving the skin-like material a purple hue.
Webb has 344 devices that must work exactly as intended. Of those, 107 are membrane release devices, non-explosive actuators that pin the sunshield in place for launch.
In total, the mission’s deployment sequence relies on 140 release mechanisms, 70 hinge assemblies, eight deployment motors, 400 pulleys, and 90 cables running a quarter-mile in length. There are also an array of bearings, springs, and gears to transform Webb from its launch to operational configuration.
With the sunshield in its diamond shape, covering an area the size of a tennis court, Webb controllers will send commands for the observatory to tension each of the five layers over two days — currently planned on Jan. 1 and Jan. 2.
“Once we get the sunshield out, that’s great, but then we have to sort of tighten it up,” Parrish said. “All five layers have different points around them where they’re connected up, and then we’ll pull on cables in each one of those corners to actually tighten up the sunshield.”
“The very last step is super important,” Puga said. “We need to tension all of the membranes using a series of pulleys and cables to create the separation between each of the five layers.”
The tensioning will separate each of the five ultra-thin kapton membranes, spacing them a few inches at the center and a few feet at the outermost edges. The tapered spacing helps allow heat from the sun to reflect between the layers, and eventually radiate back into space.
If there’s a minor tear or snag that only affects a small part of the sunshield, Webb could still accomplish many of its science goals. Three of the telescope’s instruments — the U.S.-made Near-Infrared Camera, the European Near-Infrared Spectrograph, and the Canadian Near Infrared Imager and Slitless Spectrograph — are tuned to observe the universe in near-infrared wavelengths closer to visible light.
They’re designed to work at temperatures around minus 388 degrees Fahrenheit, or 40 degrees above absolute zero. Those instruments could still be sensitive to faint infrared light if they’re a few degrees warmer, Menzel said.
Webb’s Eurpoean-built Mid-Infrared Instrument, designed to detect longer light waves, needs to be chilled 33 degrees colder than the others. A cryocooler pumping cold helium gas into the instrument will get the mid-infrared instrument to its prescribed temperature, but any deficiencies in the observatory’s sunshield might jeopardize MIRI’s science goals, which are aimed at detecting light from the universe’s oldest galaxies, and peering into star-forming dust clouds opaque at shorter wavelengths.
But any large-scale malfunction would be difficult for Webb to overcome.
“All of these single-point failures, all of these deployment mechanisms, all of the things the have to go right to make a telescope, there’s no halfway stage,” said Mark McCaughrean, a senior science advisor at ESA and an interdisciplinary scientist with observing time on Webb in its first year of operations.
“If the sunshield only half-deploys, the telescope never gets cold, the instruments won’t turn on,” McCaughrean said. “So that’s the nerve-wracking time — that first month — and after that the five months of cool down and commissioning, and then we can start doing the science.
This illustration shows the major elements of the James Webb Space Telescope. The Integrated Science Instrument Module, or ISIM, contains the mission’s four science instruments. Credit: NASA
“There’s never 100% certainty on anything like this,” McCaughrean said before the launch. “And if it fails, I think it would be an absolute catastrophe for astronomy, for space science. There’s been a lot of talk about this mission for many years, and if it does fail somewhere along the way, there will be a reckoning.
“But that’s why we feel so much pressure to have done the right job before we launched it,” he said.
Assuming no delays with the sunshield deployment, Webb’s ground team will turn their attention to moving elements of the telescope into place next week.
First will come the deployment of the secondary mirror, currently planned for Jan. 4, which focuses light from the primary mirror into the telescope’s internal focal plane, ultimately leading to Webb’s instrument detector arrays.
Then the two wings of the primary mirror will fold into place Jan. 6 and Jan. 7, according to Webb’s preliminary flight plan.
Each wing holds three of Webb’s six-sided mirror segments, with 12 mirrors fixed to the primary mirror’s central structure.
All along the way, we’re doing a lot of releases and (actuating) launch locks,” Parrish said. “We release our cryogenic cooler assembly, we have some additional radiators that we have to deploy … I don’t want to call them small deployments, but there are other deployments that don’t quite make the headlines like the sunshield does.”
Once the mirrors are in place, optical engineers will begin unlocking each segment from its launch restraint. Tiny motors behind each mirror can move it back and forth, up and down, left and right, and even slightly bend the mirror segment to bring the entire telescope into sharp focus.
“That’s a very tedious process,” Parrish sad. “They only move them a really, really tiny bit each time.”
Once Webb is in orbit around L2 next month, ground controllers will continue aligning the telescope, switch on and calibrate the instruments, and ready the observatory for science operations. All this work will occur in parallel to the natural cool-down of the telescope to cryogenic temperatures.
Engineers devised numerous emergency procedures to deal with a problem during Webb’s intricate deployment sequence. They range from options as simple as switching to a backup drive, where possible, to backing up a motor and re-attempting a deployment.
The James Webb Space Telescope inside Northrop Grumman’s factory in Redondo Beach, California. Credit: Northrop Grumman
The last-ditch options? Teams can shimmy or twirl Webb in space, or subject the observatory to fire and ice.
“A shimmy is our ability to shake Webb a little bit using its on-board propulsion system,” Parrish said. “We can actually impose some shaking into that system.
“We can also twirl the observatory, which means we can spin it at a rate to where we can put some static forces and help put some loading on an are that may be a little stubborn.
“We also have the ability to use the attitude control system, specifically the propulsion system, to be able to move Webb back and forth rapidly, so we can heat and cool a specific area that may be giving us some trouble … We call the back and forth fire and ice.
“If we’re using those tools in our toolbox, we’re not having the best of days,” Parrish said.
With Webb heading four times farther than the moon, there’s no way for astronauts to visit for repairs, like space shuttle crews serviced the Hubble Space Telescope. It also wasn’t designed for robotic servicing.
Grunsfeld, who flew to Hubble on three shuttle repair missions, said he tried to implement a late design change on Webb to make it more amenable to servicing.
“When I took over management of the science mission directorate, and by extension the James Webb Space Telescope, one of my first responses was let’s put a little grapple fixture — really small — and some targets on the James Webb, just in case we have to run it down and give it a little shake to try and deploy it.
“And I got enormous push back,” Grunsfeld said. “The design for James Webb was incredibly mature, basically finished, and mass was a concern. Even though what I proposed was half a kilogram, they said, ‘No, we can’t add any mass.'”
And there are no cameras on-board to give ground teams a visual perspective on how things are going. But any camera in a position to observe the telescope’s deployment would need to be on the “cold side” off the observatory, requiring them to be armored to withstand the super-cold, shadowed conditions.
And warmth put out by the camera electronics could interfere with Webb’s science observations.
“Anything that’s hot within the field of view of the telescope will ruin it,” Grunsfeld said.
“We have lots of little micro-switches to tell us what the configuration is exactly, so we don’t necessary need cameras. We can image it on a computer,” Grunsfeld said. “While I agree, totally, that that’s true, being visual animals, we like to see things, but we will have those animations.”
A view of the circular high-gain antenna in its stowed position on the James Webb Space Telescope. Credit: Stephen Clark / Spaceflight Now
The James Webb Space Telescope fired its rocket thrusters for the first time late Saturday to line up for course toward an observing post nearly a million miles from Earth, then deployed a high-rate communications antenna Sunday to transmit science data to the ground.
The milestones were the first major events for Webb since its successful launch Christmas morning aboard a European Ariane 5 rocket from French Guiana. The Ariane 5 placed the 13,584-pound (6,161-kilogram) observatory right on target on a course into deep space, with Webb in stretched, or elliptical, orbit with an apogee, or high point, more than a million kilometers (600,000 miles) from Earth.
After deploying its solar array and priming its propulsion system following separation from the Ariane 5 upper stage, the spacecraft fired one of its main thrusters beginning at 7:50 p.m. EST Saturday (0050 GMT Sunday) for the mission’s Mid Course Correction 1a, or MCC 1a, maneuver.
The Ariane 5 rocket aimed to deploy the nearly $10 billion observatory at a velocity just shy of the speed required to reach the L2 Lagrange point, a gravitationally-neutral spot nearly a million miles (1.5 million kilometers) from Earth, four times farther than the moon’s orbit.
The launch trajectory was selected to ensure Webb could make up the speed required to enter orbit around the L2 Lagrange point, rather than needing to turn around to use its thrusters for a braking maneuver. A burn to slow down would force Webb to point its sensitive optics toward the sun, risking damage.
The Ariane 5 rocket placed Webb almost exactly on its planned course into deep space, according to officials from NASA and the European Space Agency, which supplied the launch vehicle as part of its contribution to the mission.
Webb fired one of its four hydrazine-fueled Secondary Combustion Augmented Thrusters, or SCATs, for 65 minutes Saturday night, making up nearly all of the expected velocity shortfall needed to reach an orbit around the L2 Lagrange point.
Another burn, named MCC 1b, is penciled in the Webb flight plan Monday night. Keith Parrish, Webb’s commissioning manager at NASA, said before the launch that the MCC 1b burn might not be required, depending on the trajectory analysis following the MCC 1a maneuver.
Webb controllers at the Space Telescope Science Institute in Baltimore, Maryland, perform ranging measurements with the spacecraft using radio signals passed between Webb and ground stations around the world. The data gives engineers information about Webb’s location and speed, allowing navigators to plot future trajectory correction maneuvers. In some cases, they might not be needed, Parrish said.
Another mid-course correction burn, designated MCC 2, is planned 29 days after launch — around Jan. 23 — to inject Webb into its halo orbit around L2.
Webb has four main SCAT engines. One redundant pair is used for the MCC 1a and 1b burns, while the other redundant set is used the MCC 2 maneuver and all subsequent stationkeeping burns to keep Webb in its orbit around L2 during its science mission.
Sixteen smaller thrusters, divided into eight thruster modules each with two engines, are used for pointing control and to offload momentum from the observatory’s six spinning reaction wheels, which steer Webb toward its science targets. The reaction wheels were activated soon after Webb’s launch Saturday.
Artist’s illustration of the James Webb Space Telescope firing its engines. Credit: NASA/Goddard
With the MCC 1a burn out of the way, Webb deployed its high-rate communications antenna shortly after 10 a.m. EST (1500 GMT) Sunday, according to NASA.
The Gimbaled Antenna Assembly, or GAA, includes Webb’s 2-foot-diameter (60-centimeter) high-gain dish antenna. The Ka-band antenna will be used to transmit at least 28.6 Gbytes of science data down from the observatory, twice per day, NASA said.
Ground teams released and tested the motion of the antenna during Sunday’s deployment activity.
Before the release of the Ka-band antenna, Webb communicated to ground teams using a broad-beam S-band antenna at lower data rates. The Ka-band high-gain antenna can downlink data at a speed of up to 3.5 Mbytes per second.
Other steps completed on Webb’s first full day in space included the switch-on of temperature sensors and strain gauges on the telescope, used for monitoring Webb’s thermal and structural parameters, NASA said.
The antenna release and first mid-course correction burn set the stage for the next step of Webb’s post-launch commissioning — the deployment and tensioning of the observatory’s tennis court-sized sunshield.
The five-layer thermal barrier will keep Webb’s telescope and instruments in permanent shade, allowing the optics and detectors to reach a temperature of minus 388 degrees Fahrenheit, or 40 degrees above absolute zero. The super-cold temperatures are necessary for Webb’s infrared instruments to detect faint infrared light from the distant universe.
Two pallets containing the sunshield membranes will fold down from their launch position as soon as Tuesday, if controllers stay on the pre-planned flight schedule. That will allow for the release and tensioning of the sunshield this weekend.
Two wings holding six of Webb’s 18 hexagonal primary mirror segments are expected to fold into place in early January, building the shape of the observatory’s 21.3-foot-diameter (6.5-meter) optical surface. Then comes additional steps to align the mirror and bring it into focus, all while engineers turn on and test each fo Webb’s four science instruments.
But Webb’s time-sensitive commissioning steps — the solar array deployment and first course correction burn — are now complete. Teams have more flexibility in scheduling the remaining commissioning steps over the next six months, culminating in the release of the first science images some time in mid-2022.
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An Ariane 5 rocket, propelled by a main engine and two solid-fueled boosters, leaps off the pad at the Guiana Space Center with the James Webb Space Telescope.
The James Webb Space Telescope, a NASA-led international collaboration that took nearly 30 years and $10 billion to get to the launch pad, finally left Earth with a Christmas morning rocket ride from a European spaceport in South America, setting off on a mission to hunt for the first light in the universe. That was just the easy part.
“Webb’s scientific promise is now closer than it ever has been,” said Thomas Zurbuchen, head of NASA’s science division. “We are poised on the edge of a truly exciting time of discovery, of things we’ve never before seen or imagined.”
The telescope’s launch, running more than a decade late, had NASA officials and astronomers around the world on the edge of their seats. It’s not likely they will come off the edge until the transformer telescope finishes an unprecedented sequence of deployments to prepare for scientific observations.
“The easy part is done, now the work starts,” said Massimo Stiavelli, head of the Webb mission office at the Space Telescope Science Institute in Baltimore, Maryland. The institute, located on the campus of Johns Hopkins University, is home to Webb mission control.
The three-story-tall Webb observatory was folded up like an origami to fit inside the confines of its European Ariane 5 rocket, which was selected, in part, because it has one of the largest payload volumes of any active launch vehicle.
Now that Webb is in space, the observatory will deploy and unfurl a thermal shield the size of a tennis court, swing its mirrors into place, and gradually cool down to minus 388 degrees Fahrenheit, just 40 degrees above absolute zero, a theoretical temperature limit in thermodynamics.
Then the telescope’s sensitive infrared detectors and instrument electronics have to work. Ground teams will labor to bring the telescope’s 18 primary mirror segments into focus, an effort that could take months. Around 250,000 opening and closing windows the width of a few human hairs, called microshutters, will be calibrated to cast light detector arrays onto detector arrays.
That’s just a sampling of the pioneering technology on-board Webb. If it all works, the mission will boast 100 times the observing power of the Hubble Space Telescope, the last astronomical observatory that rivaled Webb in the scale of its ambitions.
Thanks to its ability to fold up for launch, Webb’s primary mirror will span 21.3 feet (6.5 meters) across in space, making it the largest telescope ever to leave Earth. Webb’s mirror consists of 18 individual hexagonal segments, each made of beryllium and coated in gold to aid in reflectivity.
Hubble’s monolithic mirror has a diameter of about 7.9 feet (2.4 meters).
Before Webb had a chance to open its eye on the universe, the observatory needed a lift into space to get above interference from Earth’s atmosphere.
An Ariane 5 rocket did the job Saturday with a successful takeoff from the Guiana Space Center in Kourou, French Guiana, located on the northeastern coast of South America.
After a smooth overnight countdown, the 180-foot-tall (54.8-meter) rocket lit its hydrogen-fueled Vulcain 2 engine at 7:20 a.m. EST (1220 GMT; 9:20 a.m. French Guiana time) Saturday. Seven seconds later, two powerful solid rocket boosters ignited their pre-packed powder propellant to catapult the Ariane 5 and Webb telescope off the launch pad.
After disappearing in a blanket of cloud cover, the rocket’s 27-minute flight with Webb went by like clockwork. The two strap-on boosters burned out and jettisoned, followed by release of the Ariane 5’s payload shroud nearly four minutes into the flight.
The core stage shut down and fell away from an upper stage, also fueled with hydrogen, to finish the work of placing Webb right where ground teams intended. An on-board camera on the upper stage showed Webb released from the rocket 27 minutes after liftoff, and the spacecraft extended its solar array a minute later to start charging batteries.
“The picture with the Earth in the background, with the dark sky and telescope leaving the upper stage — for me, that picture will be burned in my mind forever,” Zurbuchen said. “What an amazing Christmas present!”
“This was such a great moment on Christmas Day,” said Josef Aschbacher, director general of the European Space Agency, a partner with NASA on the Webb program. ESA was charged with providing the launch for Webb, and it used the workhouse Ariane 5 for the task.
“I’m very happy to say the team Europe has delivered, and I’m as happy to say we have delivered the spacecraft very precisely into orbit, in terms of altitude, speed, inclination,” Aschbacher said. “A good orbit injection allows more fuel on-board the spacecraft, and therefore, the James Webb Space Telescope can have a long life.”
An aerial view of the Ariane 5 launch Saturday. Credit: S. Corvaja
Webb is heading on a 29-day journey to the L2 Lagrange point, a gravitational balance location four times farther from the Earth than the moon. The observatory will slip into a halo orbit around L2, where it will point its hot spacecraft element and solar array toward the sun, and steer its frigid telescope toward deep space.
The mission is designed for at least five years of observations, and officials estimated, conservatively, that Webb could have enough propellant in its tanks to maintain its orbit for 10 years. With an on-target launch, Webb might need to burn less fuel on the journey to L2, leaving more left over for extended science operations.
The successful mission with Webb completed the 112th flight of an Ariane 5 rocket, Europe’s workhouse launcher.
“A lot of the things that we’ll do from now on are things that have never been tried on orbit before,” Stiavelli said. “They’ve been tested on the ground. Nobody has ever deployed a five-layer, tennis court-sized sunshade. Nobody has ever aligned, with exquisite accuracy, a mirror made of 18 segments.”
A rocket launch is usually the riskiest part of a space mission. That’s not the case with Webb.
“Generally speaking, the launch is on the order of 80% of the risk in a mission,” Zurbuchen said. “I would say, by our analysis and by various ways of assessing that … it may be 20% of the risk of the (Webb) mission, perhaps 30.”
Controllers at the Space Telescope Science Institute took command of Webb after it separated from the Ariane 5 launcher. They planned to calculate the spacecraft’s speed and location later Saturday, gathering data needed for a mid-course correction burn Saturday night, about 12-and-a-half hours after launch.
This infographic illustrates Webb’s journey to L2. Credit: ESA
The Ariane 5 rocket intentionally undershot the trajectory to L2, ensuring Webb would not have to fire engines to put on the brakes in the event of an over-performing launch. A braking maneuver would expose sensitive parts of the telescope to the sun.
Webb’s first rocket burn late Saturday will add a bit of speed to reach L2.
If everything goes according to plan, ground teams will command Webb to deploy its high-rate communications antenna Sunday. The observatory will begin the process of opening its sunshield as soon as Tuesday, when two pallets containing the rolled up thermal barrier will fold down ahead of and behind the telescope’s mirror.
Then a tower holding the primary mirror structure will extend to make room for the sunshield to open up, ultimately reaching a size of 69.5 feet by 46.5 feet (21.2 meters by 14.2 meters) to permanently shade the telescope.
It will take several days to unroll the five-layer sunshield, then tension the material with a system of pulleys and cables. The outermost layer, which faces the sun, is two-thousandths of an inch (0.05 millimeters) thick. The other four membranes are half that thickness.
If the sun shield tears or snags, as it did during ground testing, it could doom the Webb mission.
The next step, planned in early January, will be the folding two wings into place to give Webb’s primary mirror it’s full size. Six of the 18 mirror segments are fastened onto wings and folded back for launch, like the wings of an fighter jet on an aircraft carrier.
With the sunshield out, Webb’s telescope element and instruments, starved of sunlight, will begin cooling down to their operating temperature. Webb is scheduled to reach its operating orbit around L2 around 29 days after launch.
This illustration shows the major elements of the James Webb Space Telescope. The Integrated Science Instrument Module, or ISIM, contains the mission’s four science instruments. Credit: NASA
Controllers will switch on each of the instruments for commissioning, and use actuators to gently, and very slowly, nudge the telescope into alignment, allowing the individual segments to behave like a giant single mirror. That will allow scientists to check the telescope’s focus before beginning the operational science mission around six months from now, when NASA and its international partners plan to publicly release the first pictures from Webb.
The instruments have been bolted inside Webb’s Integrated Science Instrument Module, or ISIM, for more than seven years as the telescope moved around the country, and then between continents, on the road to launch.
The Near-Infrared Spectrometer, or NIRSpec, and Mid-Infrared Instrument, or MIRI, payloads come from Europe. Webb’s Near-Infrared Camera, or NIRCam, was built in the United States, and the observatory’s Fine Guidance Sensor and Near-Infrared Imager and Slitless Spectrograph are from Canada.
They’re all designed to be sensitive to faint light, or heat energy, from cosmic sources, whereas Hubble sees the universe in visible and ultraviolet wavelengths.
The mission will look back more than 13.5 billion years in time to see the faint infrared light from the first galaxies, revealing a previously unseen era of cosmic history that shaped the universe of today. It’s a cosmic time machine, capable of seeing galaxies and stars as they were as few as 100 million years after the Big Bang, the unimaginably violent genesis of the universe.
“This telescope is so powerful that if you were a bumble bee 240,000 miles away, which is the distance between the Earth and the moon, we will be able to see you,” said John Mather, the mission’s senior project scientist at NASA’s Goddard Space Flight Center in Maryland.
“So what are we going to do with this great telescope? We’re going to look at everything there is in the universe that we can see.”
That runs the gamut from the most distant galaxies in the cosmos, to planets, moons, asteroids, and comets in our own solar system. Webb will be able to observe everything from Mars out, seeing details undetected by every other space observatory since Galileo revolutionized astronomy with his first telescope in 1609.
The five-layer sunshield is tensioned on the James Webb Space Telescope during ground testing at a Northrop Grumman factory in California. Credit: NASA/Chris Gunn
“We want to know how did we get here,” said Mather, winner of the Nobel Prize in Physics in 2006. “The Big Bang, how did that work? So we’ll look. We have ideas, we have predictions, but we don’t honestly know.”
“This is a once in a generation event,” said Pam Melroy, NASA’s deputy administrator and a former space shuttle commander. “NASA continues to push the boundaries of what’s possible, and this is such an exciting moment. For centuries, people have looked up at sky and dreamed of trying to understand the big questions. What was the start of the universe? And is there life out there beyond Earth?”
“Webb is going take the blinders off and show us the formation of the universe,” Melroy said. “This telescope represents the kind of public good for science and exploration for which our space program was established.”
The Webb mission launched with 344 single-point failures, components that don’t have a backup. About 80% of them associated with the deployment steps, said Mike Menzel, Webb’s mission systems engineer at NASA’s Goddard Space Flight Center in Maryland.
They have to work properly for Webb to do its mission.
“Landing on Mars takes roughly a third of the single-point failures than deploying the telescope fully,” Zurbuchen said. “So it really is a level of complexity that’s over and above.”
“All of these single-point failures, all of these deployment mechanisms, all of the things the have to go right to make a telescope, there’s no halfway stage,” said Mark McCaughrean, a senior science advisor at ESA and an interdisciplinary scientist with observing time on Webb in its first year of operations.
“If the sunshield only half-deploys, the telescope never gets cold, the instruments won’t turn on,” McCaughrean said. “So that’s the nerve-wracking time — that first month — and after that the five months of cool down and commissioning, and then we can start doing the science.
“There’s never 100% certainty on anything like this,” McCaughrean said before the launch. “And if it fails, I think it would be an absolute catastrophe for astronomy, for space science. There’s been a lot of talk about this mission for many years, and if it does fail somewhere along the way, there will be a reckoning.
“But that’s why we feel so much pressure to have done the right job before we launched it,” he said.
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NASA TV will provide live video coverage of the Ariane 5 launch with JWST beginning at 3 a.m. EST (0800 GMT) on Dec. 25. The launch window opens at 7:20 a.m. EST (1220 GMT).
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If you want to see the faint, stretched-out light from the first stars and galaxies that began shining at the end of the cosmic dark ages a few hundred million years after the Big Bang, you’re going to need a big telescope. But not just any big telescope.
You’re going to need to put it in space where it will have to operate at a few degrees above absolute zero to register the exceedingly faint infrared traces of that bygone era, detecting light that has been stretched out by the expansion of space itself over nearly 14 billion years.
To do that, you’ll have to equip the observatory with a tennis court-size kite-shaped sunshade, made up of five membranes the thickness of a human hair separated and pulled taught by scores of motor-driven stainless steel cables routed through dozens of pulleys.
You’ll need to choose materials for the observatory’s structure that will retain their shape and size across enormous temperature gradients.
Then you’ll have to fold it all up so it can be crammed into the nosecone of a rocket and fired a million miles into space, hoping the vibrations and ear-splitting sounds of launch don’t dislodge a critical component so it can unfold itself, align its optics to nanometer precision and bring that feeble light to a razor-sharp focus.
That’s the Christmas holiday challenge facing the $9.8 billion James Webb Space Telescope, the successor to the 31-year-old Hubble. It is by far the most sensitive, technologically challenging — and expensive — science satellite ever built.
The spacecraft, encapsulated inside a protective nose cone atop a European Space Agency-provided Ariane 5 rocket, was rolled to the launch pad in Kourou, French Guiana, Thursday. Launch is targeted for 7:20 a.m. EST Christmas Day, weather permitting.
Once on its way, it will take a full month for the telescope to unfold like a high-tech origami, deploying its solar array, antennas, radiators, its segmented primary mirror, its secondary mirror and the complex, fragile sunshade that is so essential to success.
Another two months beyond that will be needed to carefully align the optics while the telescope continues a slow cool down to near absolute zero and then another three months or so to check out and calibrate Webb’s instruments.
And then, more than 20 years after it was first proposed, years behind schedule and billions over budget, JWST will finally be ready to take center stage on the high frontier, carrying the hopes and dreams of thousands of engineers and astronomers around the world.
“This is a high-risk and a very high-payoff program,” said NASA Deputy Administrator Pam Melroy, a former space shuttle commander. “We’ve done everything we can think of to make Webb successful. And now we just need to go do it.”
LOOKING FOR THE OLDEST STARLIGHT THERE IS
Unlike Hubble, which was placed in low-Earth orbit where space shuttle astronauts could make service calls, JWST is headed for Lagrange Point 2 on the other side of the Moon where the gravity of Sun, Earth and Moon are in balance, allowing the telescope to remain in place with a minimum of propellant.
Well beyond the reach of spacewalking repairmen, L2 offers an ideal place for Webb to chill out for its epic quest to peer back in time to the end of the so-called dark ages, when the the blazing light of the first stars burned off the hydrogen fog of creation to travel freely through space.
“It’s an infrared telescope,” said Paul Geithner, JWST’s technical project manager. “The main reason it was conceived in the first place was to see the end of the cosmic dark ages. And if you want to see objects from that epoch, the ultraviolet and the visible light they emitted so long ago has been red shifted all the way into the infrared spectrum.
“Infrared light is heat radiation. So if you want an infrared telescope to be exquisitely sensitive, first you put in space (and) besides putting in space, you need it to be super cold so that it’s not blinded by its own thermal emissions.”
Operating at L2, JWST will be less affected by the infrared background close to Earth and the scattered and re-emitted infrared light from dust in the equatorial plane of the solar system. “We need to be colder than 60 Kelvin so that we’re not limited by our own temperature,” Geithner said.
The hot side of JWST – the spacecraft bus and the bottom layer of the sunshade – will experience temperatures of nearly 230 degrees Fahrenheit. On the dark side, just beyond the fifth and uppermost layer of the sunshade, the temperature will be close to minus 390 degrees.
“That’s a huge, huge temperature differential, driven totally by these five layers on the sunshield (and) each layer is about the thickness of a human hair,” project manager Bill Ochs said in an interview.
Thirty minutes after liftoff, JWST will separate from the Ariane 5’s upper stage. Moments later, the observatory’s solar array will deploy to begin recharging on-board batteries and 12 hours after that, a thruster firing is planned to fine-tune the trajectory to L2.
Passing the moon’s orbit the day after Christmas, JWST will deploy its high-gain antenna and aim it toward Earth, giving flight controllers a high-speed data link.
Three days after launch, the two pallets holding the stowed sunshade membranes will unfold, dropping into place on either side of the Optical Telescope Element-Integrated Science Instrument Module, or OTIS. The OTIS is the actual telescope, its mirrors and instruments mounted in a carbon composite framework.
To achieve the required operating temperature, a telescoping “deployable tower assembly” will move the OTIS 48 inches away from the spacecraft’s support section, or bus, which houses relatively warm communications, thermal control and computer gear, along with the observatory’s propulsion and electrical power systems.
DEPLOYING A 1-MILLION SPF SUNSHADE
With the DTA extended, the stage will be set for the make-or-break deployment of the sunshade’s five Kapton membranes.
“The solar array deploying, the high gain antenna gimbal deploying and working are kind of standard stuff on a spacecraft and not that uncommon,” Geithner said. “And we’ve got to deploy that tower to separate the telescope from the bus to isolate it mechanically and thermally. That’s a little new, but it’s a fairly straightforward ball-screw mechanism.
“But yeah, the sun shield is where so much of the deployment risk exists because that’s where so many of the single point failures exist. And it’s just complicated.”
With the sunshade pallets already deployed fore and aft of the extended optics assembly, launch restraints will be released and protective covers rolled back to either side of the folded sunshade membranes. Two mid booms at right angles to the pallets then will extend and motor-driven cables will pull the stowed membranes out into a kite-like shape.
The five-layer sunshield is tensioned on the James Webb Space Telescope during ground testing at a Northrop Grumman factory in California. Credit: NASA/Chris Gunn
As the cables tighten, the layers will be separated and tensioned as required to ensure a slight gap between each taut layer. Near the center of the shade, the gap is as small as one inch to five inches while at the outboard corners, the separation is about a foot to facilitate heat flow. Fully deployed, the sunshade will measure 69.5-by-46.5 feet.
“The sunshield alone has 90 cables in it, that if you strung them end to end would be almost a quarter mile in length,” Geithner said. “And that’s for pulling out the membranes and tensioning them. … And, of course, we have 107 little non-explosive actuator devices, membrane release devices, that basically pin the membranes down and the covers over them for launch.”
Except for the booms, the sun shield is made up of “floppy things, and they’ll just float around in zero G and you’ll get a tangled mess if you don’t deterministically control them as much as possible,” he said.
“And so we have many little devices to constrain and ensure that all these cables and membranes and such don’t just flop around randomly and snag on something. That’s just where so much of the deployment risk is because it’s a lot of parts. They’re simple mechanisms, but there are a lot of them, and they all have to work.”
Ochs said the sunshade deploy sequence was designed to be “slow and deliberate” to give engineers time to evaluate each step in the procedure. While NASA can’t send an astronaut repair crew to the telescope, engineers have developed contingency plans to coax open jammed mechanisms.
“Whereas the mechanisms themselves are not redundant, the electronics that drive those mechanisms have redundant sides, we can go to the redundant side if there was a problem there to try to deploy it,” he said. “And then if we get to a situation where let’s say something stuck, we can shake the spacecraft using its attitude control system. We call it the ‘shimmy,’ where you can go back and forth at various frequencies and cause it to kind of shake something loose.”
Another procedure, known as the “twirl,” was developed to spin the observatory at various speeds, again to “shake something loose.”
“You can also back things up and have them start again,” Ochs said. “So if you need to back it up and give it another shot, you can do that. We’ve exercised many of these things in some of our rehearsals already, so we have these tools to help us along as we go through all these deployments.”
But what happens if there’s a serious snag, layers remain in contact with each other or membranes are torn?
This illustration shows the major elements of the James Webb Space Telescope. As the name might suggest, the Integrated Science Instrument Module, or ISIM, contains the mission’s four science instruments. Credit: NASA
Depending on the degree of thermal degradation, JWST’s three passively-cooled near-infrared instruments — the Near-Infrared Camera, or NIRCam; the Near-Infrared Spectrograph, or NIRSpec; and the Near InfraRed imager and Slitless Spectrograph/Fine Guidance Sensor, or NIRISS/FGS — should still be able to collect valuable data.
All three use 4-megapixel mercury-cadmium-telluride detectors to register infrared wavelengths between 0.6 and 5 microns. All three are designed to operate best at temperatures just below 40 Kelvin (degrees above absolute zero), but they would still work if slightly warmer.
JWST’s fourth instrument, the Mid-Infrared Instrument, or MIRI, uses 1-megapixel arsenic-doped silicon detectors to pull in wavelengths between 5 and 28 microns. It is designed to operate below 7 Kelvin, relying on a sophisticated cryocooler to pump cold helium gas from the spacecraft bus to the MIRI’s detectors.
The instrument has built-in margin, but “the real question is will the heat load on the Mid-Infrared Instrument be so high that the cryo cooler can’t overcome it? I think we’re still okay,” Geithner said. “Worst case, maybe we wouldn’t have a mid-infrared instrument. But you’d still be able to do some near-infrared science. You’d still have a mission, but it would be degraded.”
Ochs is confident the sunshade will deploy as designed based on years of testing and analysis.
“We have found things, and we’ve gone back and corrected them,” he said. “You don’t want to test it too much because the sunshield is so fragile, but we did three or four deployments and the last one, we were fully successful, we felt really good about it. It only has to work one more time. And that’s in orbit.”
HOW DO YOU LAUNCH THE LARGEST MIRROR IN SPACE? FOLD IT UP
Assuming the sunshade does, in fact, deploy normally, the next major challenge will be unfolding JWST’s mirrors starting about 10 days after launch.
The Hubble Space Telescope is a Ritchey-Chrétien Cassegrain, with a 91.5-inch primary mirror and a secondary bringing the light to a sharp focus just behind the main mirror. From there, pick-off mirrors feed the light to the telescope’s instruments.
JWST is what astronomers call a three-mirror anastigmat. Light first hits the 21.3-foot primary mirror, bounces up to the convex secondary and then down, slightly off axis, to a third elliptical mirror just behind the primary. The elliptical mirror corrects for astigmatism and widens the field of view, bouncing the light back up to a flat “steering mirror” that reflects it back down to the instruments.
The steering mirror can tip and tilt “very slightly at up to 100 cycles a second,” Geithner said, to exactly counteract any residual mechanical jitter in the system due to spinning reaction wheels and cryocooler pumps in the spacecraft bus.
Because a one-piece primary mirror would be too heavy and would not fit into an existing nose cone fairing, the observatory was designed around a segmented beryllium primary made up of 18 hexagonal sub-mirrors, each one 4.3 feet in diameter and coated with a thin layer of gold to maximise reflectivity.
Six of those segments, three on each side, were designed to be folded away for launch as was the telescope’s 2.4-foot secondary mirror. About 10 days after launch, after the sunshade is fully deployed and tensioned, Webb’s secondary mirror will be erected at the apex of three articulating booms.
Two of JWST’s primary mirror segments. Credit: Stephen Clark / Spaceflight Now
The two side panels of the primary, each with three mirror segments, then will be rotated into position to either side of the central 12 segments.
“The aperture (width) had to be at least six-and-a-half meters (21.3 feet) to gather enough light and have the same resolution at near infrared wavelengths that Hubble has at visible wavelengths,” Geithner said.
Ultra-precise optical alignment of the 18 primary mirror segments is critical. To achieve that, each segment features six mechanical actuators allowing movement in six directions. A seventh actuator can push or pull on the center of a segment to ever so slightly distort its shape if needed.
Each segment was so precisely ground and polished that if one was blown up to the size of the United States, the 14,000-foot-high Rocky Mountains would be less than 2 inches high.
Because the mirror segments will change shape slightly as the telescope cools down in space, “we basically had to build this thing perfectly wrong at room temperature so that it will be precisely correct at an operating temperature below 60 Kelvin,” Geithner said. “That’s the over-arching big challenge.”
Before alignment, the 18 segments will produce 18 separate images. Using the NIRCam instrument, engineers will map the alignment of each segment and send commands to adjust the orientation and curvature as required to produce a single, sharply-focused image.
“You’ve got to get these 18 mirrors to act as one mirror,” Ochs said. “So when we get on orbit, we go through what we call a wavefront sensing process, but really it’s the focusing process. When you start out, if you’re looking at one star, you’re going to have 18 images and you need to get that down to one.
“So we use the actuators on the back of the mirror, there are motors on the back of each mirror that allow you to move the mirrors up and down, back and forth, in and out as well as change shape slightly.”
LEARNING A LESSON FROM HUBBLE
The Hubble Space Telescope was launched in 1990 with a famously flawed primary mirror, the result of a testing error on the ground that led to spherical aberration and blurred pictures. Shuttle astronauts were able to repair the telescope by installing instruments with built-in corrective optics.
With that lesson in mind, JWST managers opted for detailed pre-launch testing to ensure Webb’s optical system will work as planned. Along with exhaustive testing of each primary mirror segment, the entire telescope was sent to the Johnson Space Center in Houston and tested inside an Apollo-era vacuum chamber that duplicated the space environment.
“We made artificial stars with light coming from the end of fibre optics and we passed light all the way through the system and we know we can line it up and make it work,” Geithner said.
And what if an actuator fails or some other problem crops up and one of the primary mirror segments cannot be properly aligned?
“We can meet all our most fundamental requirements with 17 segments,” he said. “We can try to compensate with the other segments and the secondary, it depends on if it’s within a certain range. But if it’s a bad segment, we can just tilt it completely out of the way with the remaining actuators. That’s not great … but we could still meet our level-one requirements.”
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