The James Webb Space Telescope, the successor to Hubble, is now fully assembled. What’s next for the most advanced space telescope ever constructed?
The James Webb Space Telescope (JWST) is fully assembled, as two halves of the giant observatory were pieced together on August 28. Once in space, this observatory will be the most advanced, powerful, and complex space telescope ever launched.
The top half of the package, containing the mirrors and science instruments, was lifted, via crane, on top of the spacecraft and sunshield. The top half was then carefully guided onto the bottom assembly. The merger of the two halves took place at Northrop Grumman’s facilities in Redondo Beach, California.
“The assembly of the telescope and its scientific instruments, sunshield and the spacecraft into one observatory represents an incredible achievement by the entire Webb team,” said Bill Ochs, Webb project manager for NASA Goddard Space Flight Center.
Everyone, Remember Where We Parked!
Webb will journey one million miles from home before setting its sights on targets both within our own solar system, and well beyond the Milky Way. Planets, galaxies, and moons will be examined by the JWST in infrared light.
Larger telescopes gather more light than smaller models, driving the desire of astronomers for larger observatories. The primary (main) mirror on Webb is 6.5 meters (256 inches) across, compared to the 2.4 meter (94 inch) mirror aboard the Hubble Space Telescope. This means that the JWST will be able to gather more than seven times as much light than Hubble, allowing it to see significantly dimmer objects. However, Hubble views targets over a wide range of wavelengths, including visible light, while Webb is geared toward infrared frequencies.
Infrared wavelengths are too long to be seen by the human eye, but if we could see them, they would be found just past red in the spectrum of a rainbow. Infrared waves can be detected by humans, however, a sensation we experience as heat. Some animals, like snakes, can see infrared light, just as we would perceive a different color.
Visible light bounces around the dusty clouds like those found near the center of our galaxy or in the dusty rings of young stars. Infrared light penetrates these barriers, allowing Webb to see through material which blocks the view of telescopes which can only see visible light.
Over-sized Shades ARE Coming Back Into Fashion…
Now that assembly of the JWST is complete, engineers will connect and test electrical systems. Then, the five-layer sunshield on the craft will be deployed for testing. This shield, the size of a tennis court, will block more than 99.9999 percent of the heat of the Sun, Earth, and the Moon from reaching the craft. Even the small amount of heat from these bodies could upset the sensitive instruments aboard Webb.
The gold-plated mirrors aboard the observatory are made of ultra-lightweight beryllium.
“It’s human nature to stretch, to go, to see, to understand. Exploration is not a choice, really; it’s an imperative.” —Apollo 11 Astronaut Michael Collins
The Near Infrared Camera (NIRCam) is Webb’s primary imager, designed to collect data from the earliest stars and galaxies in the visible Universe. Coronagraphs on the NIRCam will block out bright objects, revealing dimmer targets nearby. Astronomers hope these may help discover details of exoplanets surrounding alien stars.
The Near InfraRed Spectrograph (NIRSpec), splits up images into spectrums of light, to analyze the chemical composition and movement of targets. The NIRSpec has the ability to utilize microshutters to observe 100 items at the same time.
The The Mid-Infrared Instrument (MIRI) utilizes both a camera and a spectrograph to study targets in the mid-infrared portion of the electromagnetic spectrum. This camera will unveil newly-forming stars, dim comets, and will take stunning photos, similar to those seen from Hubble, but in greater detail.
The Fine Guidance Sensor / Near Infrared Imager and Slitless Spectrograph (FGS/NIRISS) consists of two devices — the FGS, which directs the fine positioning of Webb, and the NIRISS, designed to discover and study exoplanets.
Both halves of the JWST have passed tests which simulated launch, a journey to its distant home far from Earth, and the harsh conditions of space. Now that the vehicle is completely assembled, it will undergo similar testing, assuring the system is safe in its new configuration.
Time is an Illusion, Launch Time Doubly So
Liftoff of the Webb telescope has been delayed several times. Originally envisioned in 1996 as the successor to Hubble, the project was designed to cost $500 million dollars and engineers believed Webb would launch in 2007.
But, astronomy changed significantly in the 1990’s, following a wide range of discoveries about the Universe. Engineers raced to design new instruments for the spacecraft, delaying construction of the observatory. Failed tests and cost overruns pushed the launch back further, and costs rose to nearly $10 billion dollars — 20 times the expected cost.
However, NASA is currently aiming to launch the observatory, aboard an Ariane 5 rocket, in early 2021. This will mark one of the final launches for the Ariane 5 launch vehicle, which will soon be replaced by the less-expensive Ariane 6.
The JWST is an international project, with contributions from NASA, the European Space Agency (ESA), and Canadian Space Agency (CSA). Liftoff of the spacecraft will take place in from French Guiana, and data from the mission will be available to thousands of astronomers worldwide.
“It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System,” NASA describes.
While the telescope is being launched into space, it will be folded, like a piece of origami. After liftoff, the observatory will unfold like a giant Transformer.
Webb will operate 1.5 million kilometers (one million miles) from Earth, at the L2 Lagrange point, where gravitational interactions keep spacecraft orbiting with Earth as our planet travels around the Sun. This location in space is one of five similar positions along our planetary orbit, denoted L1 through L5.
“L2 is ideal for astronomy because a spacecraft is close enough to readily communicate with Earth, can keep Sun, Earth and Moon behind the spacecraft for solar power and (with appropriate shielding) provides a clear view of deep space for our telescopes,” explains Neil Cornish of the Wikinson Microwave Anistropy Probe team.
The mission, originally conceived as the Next Generation Space Telescope (NGST) was renamed in September 2002 in honor of former NASA administrator James Webb.
Running the agency from 1961 to 1968, he oversaw the development of Mercury, Gemini, and Apollo programs. When Webb took over as head of NASA, the agency had just successfully launched the first chimpanzee, Ham, into space, but had not yet lifted a human being beyond the atmosphere of Earth. Alan Shepard first touched the boundary of space just a few short months after Webb was appointed to his post.
Webb left NASA just two months before the astronauts of Apollo 8 orbited the Moon and returned to Earth, becoming the first human beings to leave low-Earth orbit.
Despite setbacks, delays, and cost overruns, the James Webb Space Telescope will, almost certainly, rewrite what we know about the Cosmos.
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