James Webb reaches its final destination

More than one million kilometres from Earth, the James Webb Space Telescope (JWST) has just taken up its post and will soon be ready to begin observing the universe.

“Webb, welcome home!” declared NASA Administrator Bill Nelson. “Congratulations to the team for all of their hard work ensuring Webb’s safe arrival at L2 today. We’re one step closer to uncovering the mysteries of the universe.”

This observatory – the largest and most powerful space telescope ever built – was folded into a rocket and launched last month by NASA, after more than 25 years of development. It has since spent four weeks zooming across space, unfurling its sunshield and mirrors along the way, to reach its final destination.

Unlike its predecessor, the Hubble Space Telescope, JWST isn’t orbiting the Earth. It’s orbiting the Sun. Its ‘home’ is the second Lagrange point, also known as L2, which is 1.5 million kilometres from Earth. This location was chosen because it’s gravitationally stable, with forces balancing out to keep the telescope in place.

Orbital trajectory diagram
Credit: Steve Sabia/NASA Goddard

This means JWST will need to use minimal fuel to perform course corrections. These will include small adjustments to stay in the intended orbit (‘station-keeping’) and counteracting the effects of solar radiation pressure (‘momentum unloading’). Though the telescope has been designed to last at least 5.5 years, NASA estimates it has enough fuel to last well beyond 10 years.

As the telescope orbits the Sun, it will always stay in line with the Earth. This alignment – plus the telescope’s tennis-court-sized sunshield – will keep JWST cool, which is important for its operation.

JWST will be studying the universe at infrared wavelengths, which means it’s very temperature sensitive – any nearby heat could interfere with light coming from stars and galaxies billions of kilometres away, so being in interstellar space is ideal.

Over the next few months, the telescope will cool down to optimal operating temperatures, ready to begin observations in June. To make this happen, engineers are embarking on a three-month process to precisely align the telescope’s mirrors and optics system.

Person stands in front of 6. 5 metre hexagonal golden mirror
Primary mirror segments are prepped to begin final cryogenic testing at NASA’s Marshall Space Flight Center. Credit: NASA/MSFC/David Higginbotham

“Everything we’re doing is about getting the observatory ready to do transformative science,” said NASA Goddard’s Jane Rigby in a press conference. “We’re a month in, and the baby hasn’t even opened its eyes yet.”

By mid-year, JWST will be ready to begin gazing back billions of years to the beginning of the universe. Astronomers have been clamouring for time on the telescope, with 300 different science projects already planned, some of which will start to answer some of the biggest questions of astronomy.

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