Randy Kimble will never forget the days in August 2017 when Hurricane Harvey battered Texas. As a project scientist for integration, test and commissioning of the James Webb Space Telescope (JWST), he had no option to hide at home. The giant telescope, at that time already 10 years behind schedule and considerably over budget, was right in the middle of one of its 100-day space simulating test campaigns at NASA’s Johnson Space Center in Houston.
“The main gate was under several feet of water and the rest of the center was shut down,” Kimble told Space.com. “But there was still one route from a hotel strip in that area and you could get in through the back gate at Johnson. Just by a matter of days, we didn’t run out of liquid nitrogen to keep the cooling system going. It was very tense.”
Kimble has worked on JWST since 2009 after spending two decades developing instruments for JWST’s predecessor, the Hubble Space Telescope. Still, he said, the tests of JWST, carried out inside the 40-foot diameter Chamber A (built in the 1960s to test equipment for the moon-bound Apollo missions), were a career highlight. They involved lowering the telescope’s temperature to the minus 390 degrees Fahrenheit (minus 217 degrees Celsius) in which it will operate, and in a vacuum similar to that of space.
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“The cryo-vacuum tests for Webb were long and gruelling,” Kimble said. “It would take weeks just to cool everything down safely and then warm up again safely at the end of the test. And in the middle, when you are cold and stable, that’s when you do your detailed testing.”
Over a six-year period, multiple test campaigns were conducted with teams working on site 24/7, including weekends and holidays, Kimble said. The spacecraft’s four scientific instruments were also tested separately, multiple times, and so was virtually every part of the telescope, the most complex, daring and expensive space observatory ever built.
Some 30 years in the making and with an eventual price tag of $10 billion, the James Webb Space Telescope is simply not allowed to go wrong. The problem is that in the space business, it is rather easy to go wrong.
Lessons from Hubble
When the Hubble Space Telescope launched in 1990, it soon became obvious something was amiss. The images it sent to Earth were disappointing, blurry, nowhere near to what scientists had expected. The problem was traced to the telescope’s great mirror, which was improperly polished during manufacturing. A rescue mission involving a team of astronauts was sent to fix the problem. Hubble received ‘glasses’ to correct its short-sightedness and turned into the astronomical powerhouse that has since generated thousands of iconic and scientifically priceless images.
With the James Webb Space Telescope, rescue missions are impossible and therefore no failures are allowed.
“James Webb Space Telescope is a prototype and with prototypes, you can always have something that goes wrong,” Mark McCaughrean, senior advisor for science and exploration at the European Space Agency (ESA) and interdisciplinary scientist at the JWST science working group, told Space.com. “That’s why JWST is so expensive. Because we’ve spent two decades building and testing every single piece a million ways to do everything to make sure it doesn’t have problems.”
But why does Webb have to be so complex? Wouldn’t a simpler mission work just as well? And why cannot it be serviced by astronauts?
The fact is that serviceability was never an option for Webb. The science it is meant to deliver, the depths of space it is intended to glimpse, simply cannot be accomplished with a spacecraft that astronauts can visit (at least not with currently available spaceships).
The first light machine
The James Webb Space Telescope, sometimes fondly referred to by astronomers as the ‘first light machine,’ was built to see the first stars and galaxies that emerged from dust and gas of the early universe, only a few millions of years after the Big Bang.
Because these stars and galaxies are so far away, the visible light they emitted when the universe was only a few hundred millions of years old has shifted into the near infrared and infrared part of the electromagnetic spectrum. This strange effect, known as the red shift in astronomical jargon, is a result of the expansion of the universe and the ensuing Doppler effect. That’s the same effect that distorts the frequency of a siren of a passing ambulance car.
Infrared radiation is essentially heat, and can be detected with special sensors that are different from those detecting visible light. Since the stars and galaxies that JWST was designed to study are so far away, the incoming signals are also extremely faint. The scientists and engineers behind JWST needed to tackle a range of technical obstacles to make this hoped-for detection possible.
Far from Earth
The Hubble Space Telescope, although originally designed to detect only the visible light of the universe (that in wavelengths that the human eye can process), was in 1997 equipped with then cutting-edge infrared detectors during the second servicing mission; these sensors were later upgraded when new technology became available. But still, infrared astronomy was an obvious afterthought for Hubble, and the telescope clearly wasn’t optimized to feel the warmth of the most distant universe.
Hubble orbits Earth at the altitude of 340 miles (545 kilometers). On top of being regularly blasted by direct sunlight, Hubble also absorbs Earth’s heat. As a result, its infrared detectors are quite dazzled by the telescope’s own warmth and it simply cannot see those faint and distant galaxies.
“If you want a really sensitive infrared telescope, it needs to be really cold,” McCaughrean said. “And to get really cold, you need to get away from Earth.”
And the James Webb Space Telescope will be far away from Earth indeed, about 1 million miles (1.5 million km) away. That’s more than four times farther than the moon. The telescope will orbit the sun, while simultaneously making small circles around the so-called Lagrange point 2 (L2) — a point on the sun-Earth axis constantly hidden from the sun by the planet. At L2, the gravitational pulls of the sun and of Earth keep the spacecraft aligned with the two big bodies.
But even that wouldn’t make Webb cold enough to accomplish its mission.
SPF 1 million
The largest piece of the spacecraft — and one without which the mission would be impossible — is its tennis court-sized deployable sunshield made of five layers of an aluminum-coated space blanket material called kapton.
The sunshield will unfurl in space before the telescope reaches its destination in one of the most nerve-wrecking parts of the spacecraft’s post-launch deployment sequence.
“The sunshield is by far the most mission-critical thing,” said McCaughrean. “If it doesn’t fully deploy, the telescope doesn’t work. We have obviously folded and unfolded it many times on the ground, but nothing like this has ever been flown in space before, and the lack of gravity simply changes things.”
The sunshield is James Webb Space Telescope’s only cooling mechanism. Nestled behind it, the mirrors and the four never-before-flown instruments will remain far below freezing at 390 degrees Fahrenheit (minus 217 degrees Celsius). The sun-facing side, on the other hand, will be incredibly hot — up to 230 degrees F (128 degrees C).
“The sunshield is like sunscreen with an SPF of at least a million in terms of how much it attenuates the solar energy,” said Kimble, then testing and integration project scientist who rode out Hurricane Harvey with JWST. “That allows us to passively cool down cold enough that [the observations] are not limited at all by the glow of the telescope.”
The sunshield is not a simple parasol; a lot of clever engineering went into its design. The five layers of the ultralight kapton material are precisely spaced so that the heat absorbed by each layer is perfectly radiated away from the spacecraft through the gaps. While superthin and ultralight, the material is also incredibly sturdy, enough to survive bombardment by meteorites.
To do what it has been designed to do, the James Webb Space Telescope really couldn’t be small. The Hubble Space Telescope, with its mirror 7.8 feet (2.4 meters) in diameter, couldn’t detect those distant early galaxies even if it were as cold as Webb.
“If you want to see those distant, faint galaxies, then you need to gather more light,” Kimble said. “And so the simple fact that Webb’s mirror collects six to seven times more photons in a given amount of time [than Hubble], gives you a significant advantage.”
The ability of a telescope to collect light increases with the square of the size of its mirror, explained McCaughrean. With its 21-foot (6.5 m) mirror, Webb will not only be able to take sharper, deeper images of the universe than those that made Hubble famous, it will also do so in a fraction of the time required by Hubble.
“Some of the deep field work that Hubble has done, they would look in a particular field for a couple of weeks,” Kimble said. “Webb can reach that kind of sensitivity limit in seven or eight hours.”
Too big for space?
But here comes another challenge. How do you lift something the size of a tennis court with a 21-foot mirror into space?
The Hubble Space Telescope, which measures 44 feet long (13.2 m) and at most 14 feet (4.2 m) across, fitted quite snugly into the 60-foot long (18.3 m) and 15-foot wide (4.6 m) payload bay of the space shuttle Discovery, from which the telescope was deployed in 1990.
But the widest rocket fairing available when Webb was designed was Europe’s Ariane 5 rocket, and the telescope’s mirror is more than 3 feet (1 m) too wide to fit. So for Webb, getting to space requires folding and unfolding. The mirror and the sunshield, as well as the usual solar arrays and antennas, must all be neatly stowed for the telescope’s launch.
Golden lightweight origami
The mirror, made of 18 hexagonal segments, each 4.3 feet (1.32 m) across, collapses like an origami for the launch. Once in space, these elements unfold, locking together. The jigsaw puzzle is so finely tuned that once the mirror is fully aligned, the seams between the individual segments will be perfectly smooth.
Aligning the mirror once in space will be an intricate endeavour of several months, relying on one of the cameras aboard the spacecraft, the NIRCam instrument.
“Aligning those mirror segments to make a smooth, continuous mirror shape out of them is going to be fascinating,” said Kimble, who will oversee these never-before-conducted operations. “At the beginning, we will produce 18 separate images with NIRCam; at the end, we will have a single beautiful image.”
NIRCam, McCaughrean said, just like many other components of the telescope, is simply not allowed to fail.
“If NIRCam failed, you won’t be able to line up the telescope,” said McCaughrean. “That’s why there is lots of redundancy in it. It has got two completely separate camera systems inside, so if one fails, you have the other one.”
At the backs of the 18 hexagonal mirror segments are small motors that delicately press onto the plates, shifting and bending them with extreme precision until they create one giant, perfectly smooth mirror.
“That means movement at the level of nanometers,” said McCaughrean. There are 25.4 million nanometers in one inch. “It’s incredibly complicated. And that’s why it takes so long for us to actually commission the telescope. We launch it in late December, but the first images won’t come until the summer of 2022 because it takes that long to line everything up.”
The mirror also needed to be extremely lightweight. Had the engineers simply scaled up the 8-foot glass mirror of the Hubble Space Telescope to build the 21-foot mirror of Webb, the telescope would be too heavy for any existing rocket to lift.
As it is, Webb’s mirror is only one 10th of the mass of Hubble’s mirror, with each of the 18 hexagonal segments, made of ultralight metal beryllium, weighing only 46 pounds (20 kilograms). The entire spacecraft, despite its enormous size, weighs only 6.5 metric tonnes compared to the 11.1 metric tonnes of the smaller Hubble.
The surface of the mirror is plated with gold, giving it the signature yellow tint. “The golden color was chosen because it’s the best for reflecting infrared radiation, much better than white or silver,” says McCaughrean.
The light reflected by the giant mirror is then concentrated onto the 30-inch (74 centimeter) secondary mirror that sits opposite the large mirror attached to a foldable tripod that must also deploy in space. From there, the light enters through an opening at the center of the large mirror into the telescope, where a tertiary mirror sends it to the detectors.
The James Webb Space Telescope launch is currently scheduled for Friday (Dec. 24). Launch day will be a big moment for the thousands of engineers and scientists who have been involved in the mission since its conception in the early 1990s.
But even after launch, the telescope, which has stretched so many people and so many technologies to their limits, will not allow them to rest. The launch will be the beginning of what Kimble described as “extended thrill,” a six-month period of gradual deployments, cooling down, switching on, aligning and testing.
“The first weeks, during our journey to L2, that’s when we will see the major deployments,” said Kimble. “The sunshield, the mirror, the secondary mirror’s support tripod, the solar wings. The telescope will build itself like an origami.”
In a press conference held on Nov. 2, Mike Menzel, Webb lead mission systems engineer at NASA Goddard Space Flight Center, said that 144 release mechanisms must work as intended for the deployment to succeed.
“There are 344 single-point-of-failure items on average,” Menzel said in that press conference. “Approximately 80% of those are associated with the deployment.”
Assuming all its deployments work as intended, Webb will be perched at L2 approximately one month after launch, hidden behind its giant sunshield. Then the telescope will perform the procedure Kimble tested in Houston during Hurricane Harvey — slowly cooling down to its operational temperature while testing its instruments and aligning its mirrors.
“We can do some rougher alignments on the way down as the system is cooling,” said Kimble. “At that stage, the structures will still be moving a little because of the cooling and shrinking, so the final tweaking can only be done after we reach temperature stability,” 100 to 120 days into the mission.
For Kimble, these months will represent a peak of his career, ensuring that he is “going out with a bang,” he said. After more than four decades working on the most cutting-edge space telescopes, the scientist said he is ready to hand over the magnificent first light machine to others after the end of its nerve-wracking commissioning period.
“It’s going to be very, very intense,” he said.
Webb telescope reaches final destination, a million miles from Earth – Arab News
WASHINGTON: The James Webb Space Telescope has arrived at its cosmic parking spot a million miles away, bringing it a step closer to its mission to unravel the mysteries of the Universe, NASA said Monday.
At around 2:00 p.m. Eastern Time (1900 GMT), the observatory fired its thrusters for five minutes to reach the so-called second Lagrange point, or L2, where it will have access to nearly half the sky at any given moment.
The delicate burn added 3.6 miles per hour (1.6 meters per second) to Webb’s overall speed, just enough to bring it into a “halo” orbit around L2, 1.5 million kilometers from Earth.
“Webb, welcome home!” said NASA Administrator Bill Nelson in a statement.
Webb will begin its science mission by summer, which includes using its high resolution infrared instruments to peer back in time 13.5 billion years to the first generation of galaxies that formed after the Big Bang.
At L2, it will stay in line with the Earth as it moves around the Sun, allowing Webb’s sunshield to protect its sensitive equipment from heat and light.
For the giant parasol to offer effective protection, it needs the Sun, Earth and Moon to all be in the same direction, with the cold side operating at -370 degrees Fahrenheit (-225 Celsius).
The thruster firing, known as an orbital burn, was the third such maneuver since Webb was launched on an Ariane 5 rocket on December 25.
The plan was intentional, because if Webb had gotten too much thrust from the rocket, it wouldn’t be able to turn around to fly back to Earth, as that would expose its optics to the Sun, overheating and destroying them.
It was therefore decided to slightly underburn the rocket firing and use the telescope’s own thrusters to make up the difference.
The burns went so well that Webb should easily be able to exceed its planned minimum life of five years, Keith Parrish Webb observatory commissioning manager told reporters on a call.
“Around 20 years, we think that’s probably a good ballpark, but we’re trying to refine that,” he said. It’s hypothetically possible, but not anticipated, that a future mission could go there and refuel it.
Webb, which is expected to cost NASA nearly $10 billion, is one of the most expensive scientific platforms ever built, comparable to the Large Hadron Collider at CERN, and its predecessor telescope, Hubble.
But while Hubble orbits the Earth, Webb will orbit in an area of space known as a Lagrange point, where the gravitational pull from the Sun and Earth will be balanced by the centrifugal force of the rotating system.
An object at one of these five points, first theorized by Italian French mathematician Joseph-Louis Lagrange, will remain stable and not fall into the gravity well of the Sun and Earth, requiring only a little fuel for adjustments.
Webb won’t sit precisely at L2, but rather go around it in a “halo” at a distance similar to that between the Earth and Moon, completing a cycle every six months.
This will allow the telescope to remain thermally stable and to generate power from its solar panels.
Previous missions to L2 include the European Space Agency’s Herschel and Planck observatories, and NASA’s Wilkinson Microwave Anisotropy Probe.
Webb’s position will also allow continuous communications with Earth via the Deep Space Network — three large antennas in Australia, Spain and California.
Earlier this month, NASA completed the process of unfolding Webb’s massive golden mirror that will collect infrared signals from the first stars and galaxies that formed a few hundred million years after the Universe began expanding.
Visible and ultraviolet light emitted by the very first luminous objects has been stretched by the Universe’s expansion, and arrives today in the form of infrared, which Webb is equipped to detect with unprecedented clarity.
Its mission also includes the study of distant planets, known as exoplanets, to determine their origin, evolution and habitability.
Next steps include aligning the telescope’s optics and calibrating its scientific instruments. It is expected to transmit its first images back in June or July.
NASA’s new space telescope reaches destination in solar orbit
NASA‘s James Webb Space Telescope, designed to give the world an unprecedented glimpse of infant galaxies in the early stages of the universe, arrived at its gravitational parking spot in orbit around the sun on Monday, nearly a million miles from Earth.
With a final five-minute, course-correcting thrust of its onboard rocket, Webb reached its destination at a position of gravitational equilibrium known as the second Sun-Earth Lagrange point, or L2, arriving one month after launch, NASA officials said.
The thruster was activated by mission control engineers at the Space Telescope Science Institute in Baltimore, with radio signals confirming Webb was successfully “inserted” into its desired orbital loop around L2.
From there, Webb will follow a special “halo” path that keeps it in constant alignment with Earth but out of its shadow, as the planet and telescope circle the sun in tandem. The prescribed L2 orbit within the larger solar orbit thus enables uninterrupted radio contact, while bathing Webb’s solar-power array in non-stop sunlight.
By comparison, Webb’s 30-year-old predecessor, the Hubble Space Telescope, orbits the Earth from 340 miles (547 km) away, passing in and out of the planet’s shadow every 90 minutes.
The combined pull of the sun and Earth at L2 – a point of near gravitational stability first deduced by 18-century mathematician Joseph-Louis Legrange – will minimize the telescope’s drift in space.
But ground teams will need to fire Webb’s thruster briefly again about once every three weeks to keep it on track, Keith Parrish, the observatory’s commissioning manager from NASA’s Goddard Space Flight Center in Maryland, told reporters on Monday.
Mission engineers are preparing next to fine-tune the telescope’s primary mirror – an array of 18 hexagonal segments of gold-coated beryllium metal measuring 21 feet, 4 inches (6.5 meters) across, far larger than Hubble’s main mirror.
Its size and design – operating mainly in the infrared spectrum – will allow Webb to peer through clouds of gas and dust and observe objects at greater distances, thus farther back in time, than Hubble or any other telescope.
These features are expected to usher in a revolution in astronomy, giving a first view of infant galaxies dating to just 100 million years after the Big Bang, the theoretical flashpoint that set the expansion of the known universe in motion an estimated 13.8 billion years ago.
Webb’s instruments also make it ideal to search for signs of potentially life-supporting atmospheres around scores of newly documented exoplanets – celestial bodies orbiting distant stars – and to observe worlds much closer to home, such as Mars and Saturn’s icy moon Titan.
It will take several more months of work to ready the telescope for its astronomical debut.
The 18 segments of its principal mirror, which had been folded together to fit inside the cargo bay of the rocket that carried the telescope to space, were unfurled with the rest of its structural components during a two-week period following Webb’s launch on Dec. 25.
Those segments were recently detached from fasteners and edged away from their original launch position. They now must be precisely aligned – to within one-ten-thousandth the thickness of a human hair – to form a single, unbroken light-collecting surface.
Ground teams will also start activating Webb’s various imaging and spectrographic instruments to be used in the three-month mirror alignment. This will be followed by two months spent calibrating the instruments themselves.
Mirror alignment will begin by aiming the telescope at a rather ordinary, isolated star, dubbed HD-84406, located in the Ursa Major, or “Big Dipper,” constellation but too faint to be seen from Earth with the naked eye.
Engineers will then gradually tune Webb’s mirror segments to “stack” 18 separate reflections of the star into a single, focused image, Lee Feinberg, Webb’s optical telescope element manager at Goddard, said during Monday’s NASA teleconference.
Alignment is expected to start next week when the telescope, whose infrared design makes it super-sensitive to heat, has cooled down enough in space to work properly – a temperature of about 400 degrees below zero Fahrenheit (-240 Celsius).
If all goes smoothly, Webb should be ready to begin making scientific observations by summer.
Sometime in June, NASA expects to make public its “early release observations,” a ‘greatest hits’ collection of initial images used to demonstrate proper functioning of Webb’s instruments during its commissioning phase.
Webb’s most ambitious work, including plans to train its mirror on objects farthest from Earth, will take a bit longer to conduct.
The telescope is an international collaboration led by NASA in partnership with the European and Canadian space agencies. Northrop Grumman Corp was the primary contractor.
(Reporting by Steve Gorman; Editing by Karishma Singh, Rosalba O’Brien and Kenneth Maxwell)
Copy or innovate? Study sheds light on chimp culture – Geo News
- Chimpanzees in one part of Guinea crack and eat nuts while others declined to do so even when offered tools, according to research.
- Professor Koops experiments to check if the chimps would develop the behaviour if tools are provided but not once did they attempt to crack a nut.
- Findings so far suggest there may be “greater continuity between chimpanzee and human cultural evolution than is normally assumed.”
TOKYO: Chimpanzees in one part of Guinea crack and eat nuts while others declined to do so even when offered tools, research published on Monday found, and the difference could shed light on their culture.
As humans, we are said to have cumulative culture: skills and technologies are transmitted and refined from generation to generation, producing behaviours more sophisticated than a single person could dream up.
Some experts believe this is unique to humans, and that traits like tool use by chimps instead develops spontaneously in individuals.
Their theory argues animals can innovate certain behaviours without a model to copy.
Evidence for this comes in part from captive chimps, who have been seen apparently independently developing simple tool use like scooping with a stick and sponging with a leaf.
But those behaviours differ from comparatively more complex techniques, like cracking nuts, and captivity is vastly different to the wild.
So Kathelijne Koops, a professor in the University of Zurich’s anthropology department, designed a series of experiments involving wild chimpanzees in Guinea.
While one population of chimps in Guinea’s Bossou does crack nuts, another group just six kilometres away in Nimba does not.
Koops wanted to see whether the Nimba population would develop the behaviour if introduced to the tools to do so.
The researchers set up four different scenarios: in the first, the chimps encountered palm nuts in shells, and stones that could be used for cracking them open.
In the second, there were palm nuts in shells, stones, but also edible palm nut fruit. In the third, they found the stones, unshelled palm nuts and some cracked nut shells.
And the final experiment offered them stones and Coula nuts, which are more commonly and easily cracked by chimpanzee populations that use the technique.
Each experiment ran for several months at a time, mostly in 2008, though in some cases as late as 2011.
But while the experiment sites in Nimba were visited and explored by dozens of chimpanzees, who were filmed with cameras installed at the location, not once did they attempt to crack a nut.
“Having observed nut cracking by Bossou chimpanzees on many occasions, it was so interesting to watch the Nimba chimpanzees interact with the same materials without ever cracking a nut,” Koops told AFP.
The study, published Monday in the journal Nature Human Behaviour suggests that nut cracking may in fact be an outcome of cumulative culture, similar to that of humans.
The researchers acknowledged difficulties studying chimps in the wild, including the inability to control the numbers visiting their sites.
Between 16 and 53 chimps visited each site during the experiments and primate behaviour specialist Professor Gisela Kaplan, who was not involved with the research, questioned whether the numbers were sufficient to draw broad conclusions.
“As in human society: the number of innovators is relatively small in animals and the expression of innovation depends also on many social and ecological circumstances and pressures,” said Kaplan, professor emerita in animal behaviour at the University of New England, Australia.
The study’s authors acknowledge there are other possible explanations for the chimps’ reticence, including the possibility that they simply weren’t motivated to eat the nuts.
But as chimpanzees in neighbouring areas do crack nuts, they consider it unlikely the Nimba population was uninterested in a new food source.
Koops said the involvement of a “normal-sized wild community” of chimps and the length of the experiments allow insights.
“Of course it would be interesting to test additional communities,” she said.
But the findings so far suggest there may be “greater continuity between chimpanzee and human cultural evolution than is normally assumed.”
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