Connect with us


‘We nailed it!’ Webb clears major hurdle with full sunshade deployment



Artist’s illustration of the James Webb Space Telescope, as it appeared Jan. 4 after sunshield tensioning. Credit: NASA

The final layers of the James Webb Space Telescope’s sunshade were robotically pulled taut with a system of motors, cables, and pulleys Tuesday, clearing a major milestone before unfolding mirrors to collect light from the oldest galaxies in the universe.

“We nailed it,” said Alphonso Stewart, Webb’s deployment systems engineer at NASA’s Goddard Space Flight Center.

The achievement means NASA has retired around three-quarters of Webb’s 344 mission-critical single-point failures, devices and components that have to work for the observatory to complete its mission.

“Today was a big day, obviously, for us,” said James Cooper, Webb’s sunshield manager at NASA. “We finished tensioning the last two layers of the sunshield, so that completes the sunshield deployment steps.”

The sunshade’s deployment and tensioning plunged the Webb telescope’s mirrors and instruments into eternal darkness, allowing the sensors to begin cooling down to minus 388 degrees Fahrenheit (minus 233 degrees Celsius), or 40 degrees above absolute zero.

The cold temperatures are necessary for Webb’s science instruments to register the faint infrared light, or heat signature, from the first galaxies and stars that formed after the Big Bang. Webb is designed to peer back to within 100 million to 200 million years of the violent birth of the universe, which occurred some 13.8 billion years ago.

The Webb telescope unfurled its sunshield into its distinctive diamond shape New Year’s Eve, guided by two mid-booms that extended from each side of the spacecraft. After pausing deployment steps over the weekend to resolve minor concerns about Webb’s solar panel power levels and motor temperatures, mission controllers on Monday started critical work to begin tensioning the five-layer thermal barrier.

Beginning with the outermost, sun-facing membrane, the first three layers of the sunshade were tensioned Monday. Mission controllers at the Space Telescope Science Institute in Baltimore, Maryland, resumed tensioning operations Tuesday morning.

Six motors positioned at tension points around the perimeter of the sunshield pulled on cables to tug each layer into its final fully taut position. Ground teams announced the final layer was tensioned at 11:59 a.m. EST (1659 GMT) Tuesday, prompting applause in the control center in Baltimore.

“MOM, I can confirm the final latch signature … which indicates that all five layers are fully tensioned,” said a member of the Webb control team to the Mission Operations Manager, Carl Starr.

Starr replied: “Significant milestone accomplished. Job well done, sunshield team. Job well done.”

“This is the first time anyone has ever attempted to put a telescope this large into space,” said Thomas Zurbuchen, associate administrator for NASA’s science mission directorate. “Webb required not only careful assembly but also careful deployments. The success of its most challenging deployment – the sunshield – is an incredible testament to the human ingenuity and engineering skill that will enable Webb to accomplish its science goals.”

The sunshield was widely considered by Webb engineers and astronomers to be the most difficult part of the mission. And that’s saying something, since Webb needs dozens of deployment steps to transform itself from launch configuration to a science-ready telescope.

NASA said Webb’s sunshield deployment and tensioning involved 139 of the mission’s 178 release mechanisms, 70 hinge assemblies, and eight deployment motors, including six for the tensioning and two for the boom extensions. There were also roughly 400 pulleys and 90 individual cables totaling around a quarter-mile in length.

The sunshield measures 69.5 feet by 46.5 feet (21.2 meters by 14.2 meters), and is designed to provide a nearly 600-degree thermal gradient between the hot spacecraft, which needs to aim its solar panel toward the sun, and the cold telescope mirrors and instruments. It has five layers, each as thin as a human hair, made of a material called kapton, supplied by DuPont, and treated with shiny aluminum. The two outermost layers have an additional purple-hued silicon coating to aid in reflectivity.

The James Webb Space Telescope’s five-layer sunshield, seen here during ground testing at Northrop Grumman’s factory in Redondo Beach, California. Credit: NASA/Chris Gunn

The tensioning separated each of the five ultra-thin 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.

The design allows Webb to passively cool its telescope, providing protection equivalent to a sunscreen with a rating of more than SFP 1 million.

Webb doesn’t have any cameras on-board to monitor its complex deployment sequence — including them could have impeded the observatory’s cool-down, officials said — so ground teams watch for telemetry signals to track the mission’s progress.

The sunshade membranes tore, and the tensioning cables developed too much slack during ground tests. No such problems appeared during the make-or-break deployment in space.

Engineers knew how many revolutions of each motor to expect, and what motor currents to anticipate before each layer was latched into place, Cooper said.

“So tracking all of those parameters give us a good indication that it went as far as we thought it would, it pulled as hard as we thought it would, therefore, it pulled in the right place,” he said. “That’s kind of the way we make those connections without any images.”

“What we’re seeing is really the heartbeat of this mechanism, and this mechanism is very intricate and very complex, but because of that, we’re able to glean so much about the hardware position, (and) the hardware resistance, from the motor telemetry,” said Hilary Stock, a sunshield deployment specialist at Northrop Grumman, NASA’s prime contractor for Webb. “So we feel very good looking at these signatures, seeing the drops in current, and understanding that that’s related to a layer latched in the correct position, and everything lined up today.”

The movement of spring mechanisms in the tensioning system gave engineers indications about the geometry and position of each layer, and that’s how ground teams were able to confirm each membrane is properly separated from the there layers, Stock said.

With the completion of the sunshield tensioning, the motors, cables, and pulleys won’t be used again.

“They’ve served their purpose, and now they’re along for the ride,” Stock said.

The Webb telescope launched Dec. 25 aboard a European Ariane 5 rocket, and performed well as it unfolded its solar array, high-gain communications antenna, and two large pallet structures that held the sunshade layers for the ride to space.

Webb extended a tower assembly last week to provide distance between the telescope’s mirrors and instruments, and the much hotter spacecraft element.

Ground teams uplinked commands for Webb to roll off covers to reveal the sunshield membranes Thursday, then extended two mid-booms out each side of the spacecraft Friday, pulling out the five sunshade layers like sheets on a bed.

That set the stage for sunshield tensioning Monday and Tuesday, following a two-day stand-down over the weekend.

“I think that the sunshield deployment certainly was the most complex (Webb deployment) in terms of moving parts having to all work in harmony, systems that interplay with each other, structures and mechanisms and cables,” Cooper said.

What’s left for Webb to complete its transformation into a working telescope are more “conventional” deployments using hinges and rigid structures, rather than the flimsy sunshade layers, Cooper said.

This infographic illustrates Webb’s journey to L2. Credit: ESA

Ground teams will turn their attention to unfolding Webb’s huge primary mirror to its full 21.3-foot-wide (6.5-meter) diameter, the biggest telescope ever sent into space. A secondary mirror, mounted on a tripod-like boom apparatus, also needs to move into place to reflect light into Webb’s instrument module, and ultimately onto detector arrays to make images and spectral measurements.

“Half my mind is going, ‘Woo hoo!,’ and half my mind is going, ‘We’ve got to get that secondary mirror out,’” said Keith Parrish, NASA’s commissioning manager for Webb, following Tuesday’s sunshield tensioning.

The secondary mirror deployment will occur first. That crucial event is slated for Wednesday, followed by folding of the port and starboard mirror wings into place at the end of the week.

Webb is cruising toward its operations post in a halo-like orbit around the L2 Lagrange point, a gravitational balance location nearly a million miles (1.5 million kilometers) from Earth. Webb’s arrival in that orbit is expected around Jan. 23, followed by five more months of instrument activations, optical focusing, and other calibration work before the science mission begins.

Email the author.

Follow Stephen Clark on Twitter: @StephenClark1.

Source: Space


Webb reaches orbital destination a million miles from Earth



Artist’s illustration of the James Webb Space Telescope. Credit: NASA

The James Webb Space Telescope slipped into orbit around a point in space nearly a million miles from Earth Monday where it can capture light from the first stars and galaxies to form in the aftermath of the Big Bang.

As planned, the European Ariane 5 rocket that launched Webb on Christmas Day put the telescope on a trajectory that required only a slight push to reach the intended orbit around Lagrange Point 2, one of five where the pull of sun and Earth interact to form stable or nearly stable gravitational zones.

The push came in the form of a 4-minute 57-second thruster firing at 2 p.m. EST — 30 days after launch at a distance of 907,530 miles from Earth — that increased Webb’s velocity by a mere 3.6 mph, just enough to ease it into a six-month orbit around L2.

“Webb, welcome home!” NASA Administrator Bill Nelson said in a blog post. “Congratulations to the team for all of their hard work ensuring Webb’s safe arrival at L2 today. We’re one step closer to uncovering the mysteries of the universe. And I can’t wait to see Webb’s first new views of the universe this summer!”

Spacecraft at or near L2 orbit the sun in lockstep with Earth and can remain on station with a minimum amount of rocket fuel, allowing a longer operational lifetime than might otherwise be possible.

An orbit around L2 also will allow Webb to observe the universe while keeping its tennis court-size sunshade broadside to Earth’s star and the telescope’s optics and instruments on the cold side.

As of Monday, Webb’s mirror had cooled down to minus 347 Fahrenheit, well on the way toward a goal of nearly 390 degrees below zero. That’s what is required for Webb to register the exceedingly faint infrared light from the first stars and galaxies.

This infographic illustrates Webb’s journey to L2. Credit: ESA

For the rest of its operational life, Webb will circle L2 at distances between 155,000 and 517,000 miles, taking six months to complete one orbit. Because the orbit around L2 is not perfectly stable, small thruster firings will be carried out every three weeks or so to maintain the telescope’s trajectory.

“Congrats to the team!” tweeted NASA science chief Thomas Zurbuchen. “@NASAWebb is now in its new stable home in space & one step closer to helping us #UnfoldTheUniverse.”

Before launch, engineers said Webb likely would have enough propellant to operate for five to 10 years. But thanks to the precision of its Ariane 5 launch and two near-perfect trajectory correction burns carried out later, it now appears Webb could remain operational for many years beyond that.

In any case, with the L2 orbit insertion burn behind then, scientists and engineers will focus on aligning Webb’s secondary mirror and the 18 hexagonal segments making up its 21.3-foot-wide primary mirror to achieve the required razor-sharp focus.

Each mirror segment is equipped with seven actuators, six of which can make microscopic changes in a segment’s orientation and one that can push or pull as required to slightly change a mirror’s shape.

As it now stands, the 18 unaligned segments would produce 18 out-of-focus images of the same star. But over the next few months, the positions of each segment will be adjusted in tiny increments, one at a time, to move reflected starlight to the center of the telescope’s optical axis.

Once all 18 light beams are precisely merged, or “stacked,” Webb will effectively be in focus, clearing the way for instrument calibration. The first science images from the fully commissioned telescope are expected this summer.

Source: Space

Continue Reading


Watch live: Cargo Dragon capsule ready to depart space station



SpaceX’s Cargo Dragon spacecraft, closing out a month-long mission, is scheduled to undock from the International Space Station Sunday after a two-delay in its departure to wait for better weather in the capsule’s recovery zone off the coast of Florida.

The gumdrop-shaped cargo freighter will undock from the station’s Harmony module at 10:40 a.m. EDT (1540 GMT) Sunday. A series of departure maneuvers using the ship’s Draco thrusters will guide Dragon away from the complex, setting up for a deorbit burn at 3:18 p.m. EDT (2018 GMT) Monday to allow the spacecraft to drop out of orbit and re-enter the atmosphere.

Splashdown in the Gulf of Mexico off the coast of Panama City, Florida, is scheduled for around 4:05 p.m. EDT (2105 GMT) Monday. Four main parachutes will slow the capsule before reaching the ocean, where a SpaceX recovery vessel will be in position to raise the Dragon spacecraft from the sea.

Time-sensitive cargo, such as biological research samples, will be flown back to Kennedy Space Center by helicopter, where NASA researchers will receive and catalog the materials for analysis and distribution to scientists around the world.

The undocking and splashdown will complete SpaceX’s 24th resupply mission to the space station since 2012 under the umbrella of two multibillion-dollar commercial contracts with NASA.

The Dragon spacecraft is packed with more than 4,900 pounds (2,200 kilograms) of cargo, including a spacesuit coming back to Earth for refurbishment after supporting spacewalks outside the space station.

The mission launched Dec. 21 from NASA’s Kennedy Space Center in Florida atop a Falcon 9 rocket. The Dragon cargo freighter docked with the space station Dec. 22, and astronauts began unpacking science experiments, holiday gifts and food, spare parts and other supplies.

The cargo delivery last month hauled 6,590 pounds (2,989 kilograms) of supplies and experiments, including packaging, to the space station’s seven-person crew.

The Dragon cargo ship delivered four experimental CubeSats to the station from teams at Kennedy Space Center, Aerospace Corp., Utah State University, and Georgia Tech. The CubeSats will be robotically deployed outside the complex later this year.

The scientific experiments launched on the SpaceX cargo freighter included an investigation from Merck Research Labs studying monoclonal antibodies. The research focus of that experiment is on analyzing the structure and behavior of a monoclonal antibody used in a drug aimed at treating cancers.

Another experiment is assessing the loss of immune protection in astronauts flying in space.

Proctor & Gamble and NASA have partnered in another experiment to test the performance of a new fully degradable detergent named Tide Infinity, a product specifically designed for use in space.

Astronauts on the space station currently wear an item of clothing several times, then discard the garment. But crews flying to the moon and Mars won’t have the same supply chain of cargo missions to support them.

NASA says Tide plans to use the new cleaning detergent to “advance sustainable, low-resource-use laundry solutions on Earth.”

Another research investigation will test manufacturing methods for superalloys in space. Alloys, materials made up of a metal and at least one other chemical element, could be produced in microgravity with fewer defects and better mechanical properties, according to NASA.

“These superior materials could improve the performance of turbine engines in industries such as aerospace and power generation on Earth,” NASA said.

With its 32-day stay at the station over, the astronauts on the research outpost replaced the cargo delivered by Dragon with materials tagged for return to Earth.

Email the author.

Follow Stephen Clark on Twitter: @StephenClark1.

Source: Space

Continue Reading


Astra fires up rocket for first time at Cape Canaveral



Astra’s small satellite launcher was test-fired at Cape Canaveral’s Complex 46 launch pad Saturday. Credit: Astra / John Kraus

Astra, a company seeking to carve out a segment of the growing small satellite launch market, test-fired its two-stage rocket at Cape Canaveral on Saturday in preparation for an upcoming demonstration flight for NASA.

The engine test-firing, called a static fire test, occurred on launch pad 46 at Cape Canaveral Space Force Station as Astra prepares to deliver four small CubeSat nano-satellites into orbit under contract to NASA’s Venture Class Launch Services program.

The rocket’s five Delphin engines, burning kerosene and liquid oxygen propellants, fired for less than 10 seconds at 11:40 a.m. EST (1640 GMT) Saturday on pad 46.

The static fire test sent an exhaust plume away from the rocket that was visible from public viewing locations several miles away. A low rumble was also heard from the beaches south of Cape Canaveral.

Astra confirmed the static fire test in a tweet Sunday afternoon. Chris Kemp, Astra’s founder and CEO, tweeted that the company will announce the target launch date and time for the mission after receiving a launch license from the Federal Aviation Administration.

The static fire test was expected to be a prerequisite for Astra receiving an FAA launch license.

Astra’s rocket is small in size compared to other launch vehicles that regularly fly from Cape Canaveral. The launcher, called Rocket 3.3 or LV0008, stands just 43 feet (13.1 meters) tall, more than five times shorter than SpaceX’s Falcon 9 rocket, and about the same height as the Falcon 9’s payload compartment.

The commercially-developed launch vehicle, in its existing configuration, is designed to carry a payload of around 110 pounds (50 kilograms) into a 310-mile-high (500-kilometer) polar orbit, according to Kemp. Astra’s rocket is sized to offer dedicated rides to orbit for small commercial, military, and research satellites.

Astra launched its first successful mission to low Earth orbit in November from Kodiak Island, Alaska, on a test flight sponsored by the U.S. Space Force, following three previous launch attempts that faltered during the climb into orbit.

Founded in 2016, Astra aims to eventually conduct daily launches with small satellites at relatively low cost, targeting a smallsat launch market cramped with competitors such as Rocket Lab, Virgin Orbit, and Firefly Aerospace, each of which has begun flying small launch vehicles. Numerous other companies are months or years away from debuting their smallsat launchers.

Four CubeSats are set to ride the rocket into orbit on a mission arranged by NASA.

The mission is part of NASA’s Venture Class Launch Services, or VCLS, program, which awarded Astra a $3.9 million contract last year for a commercial CubeSat launch. Scott Higginbotham, head of NASA’s CubeSat Launch Initiative at Kennedy Space Center, says the agency is the sole customer for the upcoming Astra launch.

The Venture Class Launch Services program is aimed at giving emerging small satellite launch companies some business, while helping NASA officials familiarize themselves with the nascent industry.

NASA previously awarded VCLS demonstration missions to Rocket Lab and Virgin Orbit, which completed their first launches for the U.S. space agency in 2018 and 2021. The U.S. military has awarded similar demonstration launch contracts to Astra and other companies.

Higginbotham said the VCLS mission gives NASA insight into companies’ management and technical teams, procedures and processes, and their hardware designs.

“That’s going to allow us to be a better consumer going forward if they stay in business, and can offer their services to us later on,” Higginbotham said. “We’ll already have been introduced and have done a deep dive, of sorts, into those companies to understand what makes them tick, and that’s that’s of tremendous value to us.”

The VCLS demo missions are also a stepping stone toward certification of the new smallsat launchers to carry more expensive NASA satellites into orbit. The certification isn’t required for the demo missions themselves.

“NASA has other missions that require a little bit more reliability from the launch vehicle, a little more certainty, and a little more launch vehicle insight,” Higginbotham said.

Student teams work on the INCA CubeSat set for liftoff from Cape Canaveral on Astra’s small satellite launcher. Credit: New Mexico State University

A team of fewer than a dozen technicians and engineers set up Astra’s rocket on pad 46 earlier this month. Astra’s launch control team remained behind at the company’s headquarters in Alameda, California, where managers remotely control the rocket’s countdown.

A fueling test, or wet dress rehearsal, was accomplished earlier in January before Saturday’s static fire.

NASA assigned four nano-missions to the Astra demonstration launch through the agency’s CubeSat Launch Initiative program.

One of the CubeSats was developed by the University of California, Berkeley. Named QubeSat, the small spacecraft will test a tiny gyroscope, a device used to help determine the orientation of satellites in space.

Another student-developed payload on Astra’s first launch from Florida is the Ionospheric Neutron Content Analyzer, or INCA mission, from New Mexico State University. INCA’s main science instrument is a directional neutron spectrometer from NASA’s Goddard Space Flight Center.

Data from INCA will “contribute to understanding the radiation environment that satellites encounter, and to the understanding of neutron air showers, which pose a radiation hazard to occupants of high-altitude aircraft such as airliners,” according to the student team that developed the mission.

The BAMA 1 mission, developed at the University of Alabama, will demonstrate a drag sail device designed to help old satellites and space junk drop out of orbit. The drag sail will encounter air molecules from the rarefied atmosphere at the satellite’s altitude, slowing its velocity enough to fall back to Earth.

The final payload is a CubeSat named R5-S1 from NASA’s Johnson Space Center in Houston. NASA says the mission’s objectives including demonstrating quick CubeSat development and testing technologies useful for in-space inspection, which could make human spaceflight safer and more efficient.

Another CubeSat mission from UC-Berkeley originally selected by NASA for the Astra demonstration launch wasn’t ready in time for integration with the rocket in December, according to Jasmine Hopkins, a NASA spokesperson at Kennedy Space Center.

The CubeSat Radio Interferometry Experiment, or CURIE, mission, consists of two identical three-unit CubeSats, each the size of a shoebox, with radio antennas to detect emissions from solar activity, such as solar flares and coronal mass eruptions.

NASA will assign the CURIE satellites to another launch, Hopkins said.

Email the author.

Follow Stephen Clark on Twitter: @StephenClark1.

Source: Space

Continue Reading