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James Webb Space Telescope Reaches ‘Lagrange Point 2’; Poised to Peer Deep Into the Universe’s Past

Published: January 24, 2022
The James Webb Space Telescope (JWST) has reached its final resting place at the Lagrange Point 2, a relatively stable area in space where it will be calibrated and prepared to peer deep into the universe’s past. (Image: NASA/Desiree Stover CC0 1.0)

On Jan. 24, the James Webb Space Telescope (JWST) successfully reached its observation point dubbed the “Lagrange Point 2” (L2) some 1.5 million kilometers (932,057 miles) from Earth on its nightside. 

After a roughly 30 day trip through the vacuum of space the JWST was nudged into place with a short five-minute thruster burst. Over the coming months, operators on Earth will tune the telescope to get it ready to peer billions of years into the past, some 250 million years after the theoretical Big Bang. 

The next task for scientists includes switching on four instruments attached to the telescope and focusing its primary reflector which spans 6.5 metres.

Charlie Atkinson, chief engineer, told the BBC, “There’s a pretty intensive effort to take all of those 18 segments from their current state and get them to act as one big mirror, and also to get the secondary mirror into its optimised condition,” adding that, “We do this using the science images, which is why we need to get the science instruments activated and checked out with some initial calibration work.”

The JWST is the successor to the infamous Hubble Space Telescope and was launched on Dec. 25 by an Ariane-5 rocket from French Guiana. The telescope has the ability to capture images of the very first stars forming in the universe and to identify distant planets to see if they may be habitable. 

While Europe’s Ariane-5 rocket gave the telescope a near perfect trajectory and velocity to make the trip to the L2 scientists did have to initiate two course correction burns — not including its final thruster burn — to get the telescope to its planned destination.  

The L2 point was chosen because it is located in one of five gravitational “sweet-spots” in the solar system where satellites can hold their position with few orbital adjustments, thus conserving fuel. The telescope has enough fuel to continually operate for approximately 20 years.

The position also serves up the perfect temperature for the telescope to operate. The JWST is designed to view the universe in infrared light and must maintain super-cold conditions for its hardware to work. A large sunshield blocks the sun’s rays from hitting optics and instruments on the JWST, cooling them to about -230 Celsius (-382 Fahrenheit).

Since the telescope uses infrared light it has the ability to peer through dust to see stars that otherwise would be obscured. 

Jean-Paul Pinaud, who leads the Northrop engineers that keep the JWST on track told the BBC, “L2 is pseudo-stable. The flight operations team is preparing routine station-keeping burns. They’ll be doing those every 20 days or so with the trajectory calculations provided by our flight dynamics team. We’ll set them up in a similar way, and then fire the thruster. But the burns will be quite small.”

The team in charge is in the midst of calibrating the telescope and aligning its 18 individual mirror segments, an endeavor that is expected to take upwards of three months. The alignment of the mirror segments will be brought down from millimeters to nanometres.

“Similar adjustments will be applied to the 74cm-diameter secondary reflector which sits out in front of the primary mirror and is used to bounce light back towards the instruments,” the BBC reported. 

Kyle Hott, the mission systems engineering lead at Northrop told the BBC, “It’s pretty incredible to think that it was all just a concept on paper decades ago, and now it’s actually here, arriving at L2. Morale is high and we’re so very excited.”