Webb Space Telescope Arrives at L2

Webb Space Telescope Arrives at L2

The $10 billion James Webb Space Telescope arrived at its destination a million miles from Earth today after a month-long journey. At 2:00 pm Eastern Standard Time, NASA fired the spacecraft’s thrusters for 5 minutes, putting it into a halo orbit around a point in space called the Sun-Earth Lagrange Point-2, or L2 for short.

Launched on December 25, 2021 from Kourou, French Guiana on Europe’s Ariane 5 rocket, JWST has been making its way to L2 for the past 30 days. L2 is a point of gravitational near-equilibrium in the Sun-Earth system where little fuel is required to maintain the orbit. It will remain there throughout its operational lifetime.

NASA’s “Where is Webb” website has been keeping the public up to date all along the 1 million mile (1.5 million kilometer) route to L2. The countdown reached zero miles to go just after 2:00 pm ET.

JWST will make one orbit of the L2 point every six months, with the thrusters firing at approximately 21-day intervals to keep it in the right place.

The telescope’s lifetime is largely dependent on how much fuel it has and everyone is eager to find how long that might be. Officially, NASA designed JWST with a 5-year lifetime, but the fuel availability was based on 10 years of operations. Using that measure, expectations now are that it will far exceed that span.

NASA JWST commissioning manager Keith Parrish of NASA’s Goddard Space Flight Center enthusiastically told reporters today that 20 years is not out of the question. The Ariane V rocket put the telescope on such a precise trajectory that only about one-third of the fuel allocated for getting to L2 was needed for mid-course corrections.What’s left can be used for extended operations.

We’re going to extensively exceed our 10 year life. You’ve heard numbers around 20 years. We think that’s probably a good ballpark, but we’re trying to refine that. … We’re all going to be thrilled. — Keith Parrish

Reaching L2 is another milestone in JWST’s commissioning for science operations, but not the final one.

The 6.5 meter (21.3 foot) diameter telescope was too big to fit in the Ariane 5 rocket and had to be folded up. That meant it had to go through a complicated unfolding process during the first two weeks it was outbound to L2. The deployment was successfully completed on January 8.

Then the 18 gold-plated segments of the primary mirror were moved half an inch forward from their stowed positions to begin the months-long process of focusing them into a smooth surface that can acquire a single sharp image instead of 18 fuzzy ones. Each of the 18 segments has seven actuators on the back to change the shape. The secondary mirror has some too. Lee Feinberg, optical telescope element manager for JWST at NASA/Goddard, told reporters today that all 132 are functioning properly.

Infrared light is collected by the James Webb Space Telescope’s gold-plated primary mirror, reflected into the secondary mirror at the end of the tripod-structure (covered in black) and directed back into the four instruments in the center of the primary mirror. Credit: NASA

Scientists are eager to see what JWST will reveal about the universe, but it will take about five more months before the telescope is ready.

NASA expects to begin the process of aligning the primary and secondary mirrors next week. That will take about three months. Feinberg said they will use the star HD 84406 in the Ursa Major constellation, a bright isolated star near the bowl of the Big Dipper, as the focusing target.

Then it will be another two months before the four scientific instruments are ready for duty. JWST is a cooperative program among NASA, the European Space Agency, and the Canadian Space Agency. The Near-Infrared Camera (NIRCam) was provided by the University of Arizona, the Near-Infrared Spectrograph (NIRSpec) by ESA, and the Mid-Infrared Instrument (MIRI) jointly by NASA and the European Consortium (led by the U.K.) with ESA. Canada provided the Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS).

It takes time to get them down to the very cold temperatures at which they need to operate. JWST is an infrared telescope searching for heat signatures in the universe, so the telescope itself must be extremely cold. NIRSpec, NIRCam, and FGS/NIRSS operate at 40° K (-387°F/-233°C). They can get down to that temperature passively just by being on the cold side of the telescope, protected by the sunshield that blocks solar radiation as well as light from the Sun, Earth and Moon. MIRI operates at 7 degrees Kelvin (-447°F/-266°C) and requires a closed-loop cryocooler in addition.

JWST is years behind schedule and billions over cost. NASA currently estimates the development cost at $8.8 billion, a figure that mushroomed over the past 25 years. That does not include money spent by ESA (about $860 million not including launch) and CSA (US$160 million) for development, or operations costs. NASA estimates 5 years of operations at $900 million.

The program survived a congressionally-directed independent review in 2010, termination threats, and breaching a congressionally-set $8 billion budget cap by 10 percent in 2018. During a congressional hearing that year, the then-chair of the House Science, Space, and Technology Committee, Rep. Lamar Smith (R-TX), said by his calculations JWST was 19 times its original cost estimate with a 14-year delay. He and others in Congress continued to support the program, however, because of its promised scientific breakthroughs

Though that support has been bipartisan, it was Democrats congratulating NASA today. Current House SS&T Committee chair Rep. Eddie Bernice Johnson (D-TX) and space subcommittee chair Rep. Don Beyer (D-VA) said they are looking forward to seeing the first images. “Congratulations to NASA and its international and contractor partners on bringing Webb one step closer to transforming our understanding of the universe,” said Johnson. Beyer added that he “eagerly” awaits “the revelations JWST will deliver once final tests are completed and the telescope is fully deployed.”

House Appropriations Committee Democrats were similarly enthusiastic.

House Majority Leader Steny Hoyer (D-MD), whose district includes NASA-Goddard, tweeted his approval.

Sen. Chris Van Hollen (D-MD), a member the Senate Appropriations subcommittee that funds NASA and successor to the legendary Sen. Barbara Mikulski who saved JWST from deep cuts, offered his own congratulations.

Somewhat surprisingly, as of press time Vice President Kamala Harris, chair of the White House National Space Council, had not offered any public comment. NASA Administrator Bill Nelson was the highest-level Biden Administration official weighing in on his agency’s achievement.

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