NASA's $ 10 billion James Webb Space Telescope will study the origin of the universe
For the past 31 years, the Hubble Space Telescope has been an inevitable observational platform for astronauts but it has begun to show that it is overdue. Last serviced in 2009, the telescope has had to go into "safe mode" partial shutdown several times over the last few years - most recently, this October. And while optimistic estimates suggest Hubble could remain operational through the end of the decade, NASA, with its ESA and CSA partners, has spent more than a dozen years developing a fan, Space Telescope James Webb (JWST). When the Webb launches - now ready to build on Christmas Day - it will take over as humanity's positive eye in the skies for decades to come.
The 7.2-ton JWST is NASA's largest orbital telescope. Its 6.5-meter primary mirror area - made up of 18 gold-plated hexagonal sections - is more than twice the size of Hubble and nearly 60 times larger in area than the Spitzer Telescope, retired in 2022. The sun shield it uses to protect it has its delicate infrared sensors as far as a tennis court, and its telescopic equipment is entirely three stories high. The 458 gigabits of data collected each day will first be routed through NASA's Deep Space Network, then sent to the Space Telescope Science Institute in Baltimore, Maryland, which will collect and disseminate that information to the largest astronomical community. .
When it reaches its orbital home at the L2 Lagrange point 930,000 miles from Earth, the JWST will begin its four-point mission: finding light from the earliest stars after the Big Bang; studying the formation and evolution of galaxies, studying the evolution of stars and planetary systems; and seek the origin of life.
To do so, the Webb takes a different approach from the previous Hubble. While the Hubble looked at the universe in the visible and ultraviolet spectra, the JWST sees in infrared, just as the Spitzer did but with much greater resolution and brightness. The use of this infrared is critical to Webb's mission as that wave can peer through clouds of interstellar gases and dust to see things that are otherwise hidden.
The Webb camera series is made up of four separate components: the Infrared Medium Infrared (MIRI), Near-Infrared (NIRCam) Camera, Near-Infrared Spectrograph (NIRSpec), and the Near-Infrared Image red and Slitless Spectrograph / Fine Directional Sensor. (NIRISS / FGS). These instruments are so sensitive that they can detect their own heat radiation during operation. To reduce these infrared emissions, three of the sensors are cooled to 388 degrees Fahrenheit (-233 degrees C). The particularly sensitive MIRI is cooled even further to -448 degrees F (-266 degrees C) - that is just 7 degrees Kelvin above absolute zero.
Getting the MIRI so cold is not easy. After the JWST enters orbit, the telescope spends weeks slowly cooling the sensor to optimum operating temperature using a helium-based cooling system.
"It's relatively easy to cool something down to that temperature on Earth, usually for scientific or industrial applications," Konstantin Penanen, a JPL cryocooler expert said in a recent NASA blog post. “But these Earth-based systems are very bulky and energy efficient. For a space observatory, we need a physically compact, high - energy cooler that needs to be highly reliable because we cannot go out and repair it. So those are the challenges that lay ahead, and in that regard, I would say that the MIRI cryocooler is definitely at the forefront. ”
The extra effort required by MIRI is well worth it as ground - based infrared telescopes - especially those that operate within the mid - infrared spectrum such as MIRI - are largely blocked by heat emissions from the devices themselves and the surrounding atmosphere.
“With the other three instruments, Webb monitors waves up to 5 microns. Sending waves to 28.5 microns with MIRI greatly increases their field of science, ”George Rieke, a professor of astronomy at the University of Arizona, said earlier this month in a NASA blog. “This includes everything from examining protostars and the protoplanetary discs around them, the energy balance of exoplanets, huge loss from evolutionary stars, circumnuclear tori around the black holes in the middle the active galactic nucleus, and much more. ”
With low specific JWST requirements at low temperatures, it is essential that the telescope's sensor array be kept out of direct light (and blocked from other light sources such as the Moon and Earth). To ensure that these cameras are under constant shade, NASA engineers have built a five - level sunshield made from Kapton film with aluminum coating to keep them in the cold, chilly darkness.
“The shape and design also directs heat out the sides, around the edge, between the layers,” said James Cooper, JWST Sunshield Manager at the Goddard Space Flight Center. "Heat generated by the spacecraft bus at the heart, or center, is forced out between the organ layers so that the optics cannot heat up."
Measuring 69.5 feet by 46.5 feet by .001 inches, the kite-shaped sunshade is stacked five rows high so that energy captured by the high ceiling radiates out into space between them, making each continuous fold a little colder than the one above. In fact, the temperature difference at the outermost (383K, or 230 degrees F) and inner (36K, about -394 degrees F) ranges is about the order of magnitude.
To gather enough light to reach the farthest, most visible stars - some as far as 13 billion light-years away - the JWST will rely on its large 6.5m primary mirror range. Unlike the Hubble, which used a single 2.4m wide mirror, the Webb mirror is divided into 18 separate compartments, each weighing just 46 pounds due to their beryllium construction. They are covered in gold to form their reflections of infrared and hexagonal light so that, when grouped together in orbit, they converge rapidly to form one reflective plane, no gaps, no gaps. Their small size also allows them to be sculpted up and folded down so that they are within the tight confines of the Ariane 5 rocket where they cycle into orbit.
The place of coordinating these segments to focus on one place in a distant galaxy falls into the actuator assembly of the mirrors. Seven small motors sit behind each mirror section (one at each corner and seven in the middle), enabling precise control of the steering and bending. “Aligning the main mirrors as if they were one large mirror means that each mirror is attached to 1 / 10,000th thick of human hair,” said Webb Optical Telescope Element Manager Lee Feinberg.
After a further 20 years of development and delay, costing $ 10 billion and involving the efforts of more than 10,000 people, the Webb Telescope is finally ready for launch - and hopefully this time e. The program saw delays, after delays, after delays on its start schedule. NASA abandoned the first date of March 2022 due to the original COVID-19 revolution and the associated locks - although, to be fair, the January 2022 GAO was only on give the JWST a 12 per cent chance to go off the ground by the end of this year - and a vague "sometime in 2022" timetable for its launch.
NASA revised that estimate to a company “sometime in October 2022,” finally settling on a Halloween launch window, only to postpone it again until late November / early December. In fact, the beginning of December came quickly at the end of December, especially the 22nd, which was brought back to its current date of December 24th. In fact, do that on the 25th.
This delay is caused by the various factors that go into getting an instrument of this size and sensitivity ready for launch. After completion of the construction work, the JWST had to go through a fully tested battery, then gently load it into a shipping container and transport it to the launch site in Kourou, French Guiana. Once there, the actual prepping, fueling and loading of JWST on the Ariane 5 rocket took another 55 days.
That timeline was further extended as a result of an "incident" on November 9 where a "sudden, unplanned release of a clamp band - which holds Webb to launch the vehicle 's adapter - caused a vibration. throughout the theater, ”all NASA. The Webb anomaly review board initiated a further round of testing to ensure that these vibrations did not damage other components or knock anything significant out of alignment.
Now that the telescope is rated A-OK, final preparation is underway. Overcoming any other obstacles, the JWST will launch at 7:20 ET on Christmas Day (stay tuned here!) To begin the 30-day, 1.5 million kilometer journey out of the Lagrange 2 where he spends two weeks slowly unlocking the mirrors and the view of the sun, then begins to explore the depths of the universe.
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