The largest, most expensive and most sophisticated space telescope ever made is scheduled to lift off on Dec. 25 from the north coast of South America. At its eventual orbital station 932,000 miles (1.5 million km) from Earth, the James Webb Space Telescope might just see to the beginning of time.
The farther one looks in space, the further back in time one goes. When Webb begins its work in mid-2022, it will help scientists study some of the earliest light in the universe and peer more closely at planets in other galaxies. More than 30 years after NASA launched the Hubble Space Telescope, its much bigger successor is designed to see through the most ancient mists of deep space.
The almost $11 billion (¥1.24 trillion) telescope, more than two decades in the making, is a National Aeronautics and Space Administration (NASA) collaboration with the European and Canadian space agencies. It’s currently scheduled to launch early on Dec. 25 from the European Space Agency’s South American spaceport in French Guiana aboard an Ariane 5 rocket.
For science, the Webb telescope’s ultimate promise is a greater understanding around two fundamental questions for humanity: Where did we come from and are we alone? But for NASA, it’s also a huge risk given everything that might go wrong.
The telescope is “a shining example of what we can accomplish when we dream big,” NASA Administrator Bill Nelson said Dec. 21 at a pre-launch briefing, calling it “one of the great engineering feats for the people of this planet.”
The Webb telescope will examine the infrared spectrum-thermal radiation humans can’t see and which is often obscured to ground-based telescopes. Hubble is still working, albeit from an orbit much closer to Earth (340 miles/547 km away), collecting data in the visible light spectrum. The older telescope, which had to be repaired after launch because of a flaw in its mirror, has been repeatedly updated with new technology and could last another two decades.
But researchers say Webb, named for NASA’s administrator during its heyday of the Mercury, Gemini and Apollo rocket programs in the 1960s, is crucial to a deeper understanding of the early universe and how stars and galaxies formed. New insights are expected from discoveries dating back 13.5 billion years, only a few hundred million years after the Big Bang. The Webb will also be able to peer more closely at objects first uncovered by Hubble, many of which are obscured by interstellar dust and gas that the newer telescope can pierce.
The Webb’s skill set will also include observation of planets — some possibly like Earth — that orbit stars in other galaxies. One Webb target is the Andromeda galaxy, the closest to our Milky Way, which reveals far more of its nature in the infrared spectrum than in visible light. The telescope also has multiple forms of spectrograph imaging to study the composition of stars and planets.
But before any of this research can happen, Webb must arrive at its station. First, the launch itself must be successful. Then the telescope must execute a daunting series of maneuvers, with the first 13 hours of flight including two critical tasks. Roughly 33 minutes after liftoff, Webb must deploy its solar array to begin generating power. Then about 12 hours later, the craft must initiate a course-correction rocket burn to fine-tune its trajectory toward its final destination.
Both must happen precisely on cue, long before Webb completes the 29-day trip to its post.
The telescope’s workstation is called the second Lagrange point, or L2, “behind” the Earth as viewed from the sun. The spot is one of five such points where the gravity of the sun and Earth balance to allow a spacecraft to move along with them. This reduces the amount of propellant needed for the craft to maintain its orbit.
The dark and cold of space are integral to Webb’s infrared work. After rolling out its solar array, the Webb must accomplish additional “unfoldings.” The craft will need to deploy a large scaffold structure to support a sunscreen that shields it from heat and light, followed by a five-layer Kapton sunscreen. The telescope, operating at temperatures below -380 Fahrenheit (-229 Celsius), will always point away from Earth, the sun and moon.
Following those maneuvers, the spacecraft will then unfold 18 small, hexagonal mirrors that fit together down to the nanometer, together comprising the telescope’s 6.5 meters (21.5 feet) mirror. After assembly and arrival at L2, the Webb will have six months of mirror alignment, instrument calibration and other testing before it begins its mission.
If successful, the Webb’s ascent will undoubtedly cheer thousands of scientists who have watched in despair as multiple miscues, soaring costs and slipped deadlines bedeviled the project, which Congress nearly scuttled 10 years ago due to the steep budget overruns. The main contractor is Northrop Grumman Corp.
The Webb is likely to have its earliest “wins” in the area of exoplanet observations, planets that orbit stars in galaxies far from our own, said Alex Ji, a near-field cosmologist and assistant professor at the University of Chicago.
“I think this is going to have an impact on the same level as Hubble,” Ji said, noting the iconic images that telescope collected, capturing the public’s imagination. “What speaks to the power of this telescope across the entire span of astrophysics is how many people are excited about it.”
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