When can we expect James Webb Space Telescope’s first images?

By Govert Schilling

Published: Monday, 28 February 2022 at 12:00 am

After 25 years and over 10 billion US dollars, on Christmas Day 2021, the James Webb Space Telescope (JWST) was finally launched into space by a European Ariane 5 rocket.

With its 6.5-metre primary mirror and its tennis-court-sized sunshield, Webb had to be folded up to fit in the rocket’s fairing, only to be deployed step by step in the first two weeks of its mission.

Now, we’re all eagerly awaiting the first proper images of space captured by the James Webb Space Telescope, which should be captured around June or early July 2022.

Find out how James Webb Space Telescope will study galaxies, and how James Webb Space Telescope will study exoplanets.

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The launch of the James Webb Space Telescope aboard Arianespace’s Ariane 5 rocket from French Guiana on 25 December 2021. Credit: Jody Amiet/AFP via Getty Images

Currently, the James Webb Space Telescope is aligning its primary mirror using its Near Infrared Camera (NIRCam) instrument, which has resulted in the image below: a mosaic of the same star captured 18 times.

This seemingly chaotic capture is a result of JWST’s unaligned mirror segments reflecting light back into the telescope’s instruments, and is a vital part of preparing Webb for producing beautiful images of the Universe.

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A mosaic of the same star captured 18 times captured by James Webb Space Telescope. This image was used by NASA scientists to align JWST’s primary mirror. Credit: NASA

A total of three mid-course correction manoeuvres successfully placed the huge space telescope in a slow looping orbit around the second Lagrange point (L2), a stable gravitational point some 1.5 million kilometres behind Earth as seen from the Sun.

“But a lot more needs to be done before we can start science operations,” says Mark McCaughrean, the Senior Advisor for Science and Exploration at ESA (the European Space Agency), NASA’s main partner in the programme.

For one, the telescope and its sensitive instruments, which left the French Guiana launch platform at tropical temperatures, have to cool down to 230˚C below zero.

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In this image captured by cameras on the upper stage of its Ariane 5 rocket, JWST sets off on its 1.5 million km voyage to L2 after separating on 25 December 2021. Credit: Arianespace/ESA/NASA/CSA/CNES

Thanks to its giant multi-layer sunshield, JWST had already reached –200 °C by early January 2022, but the passive cooling slows down over time.

It’s a delicate process, says McCaughrean. The optics can never be the coldest parts of the telescope, lest molecules released as gases from the graphite-composite support structure freeze down on the mirrors, degrading its performance.

When the NIRCam instrument (Near Infrared Camera) got cold enough for its sensitive mercury-cadmium-telluride detectors to pick up infrared light, the process of aligning the telescope’s 18 mirror segments could finally commence.

Each hexagonal segment is fitted with seven actuators and can be slightly tilted, shifted, rotated and deformed to ensure that they operate together as one perfect parabolic surface.

And since the alignment procedure is done with starlight, the image above marks JWST’s ‘first light’.

But it will take months of incremental precision adjustments before the 18 individual stellar images from each mirror are all brought together into one single focus.

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Webb will orbit the L2 point, keeping the Sun, Earth and Moon behind it for a clear view of deep space.

Testing JWST’s instruments

Around late April 2022, engineers will also start commissioning JWST’s four large science instruments:

  • NIRCam (Near InfraRed Camera)
  • NIRSpec (Near InfraRed Spectrometer)
  • MIRI (Mid InfraRed Instrument
  • FGS/NIRISS (Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph).

Equipped with beam splitters, filters and micro-shutters, all have different observing modes, and these have to be fully tested and calibrated before they are handed over to the astronomy community.

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MIRI (left) being integrated into JWST’s science payload module at NASA’s Goddard Space Flight Center in 2013. Credit: NASA/C. Gunn

“Of course, every instrument has been tested and checked on Earth,” says McCaughrean, “But we need to prove that they also perform flawlessly in space.”

So what about that supposedly awe-inspiring first picture taken by the James Webb Space Telescope? That’s not expected until some six months after launch, which would be late June or early July 2022.

“What it will show is a closely guarded secret. Most likely some kind of star-forming region,” says McCaughrean.

The first round of science observations won’t start before summer 2022.

Astronomers can’t wait to train their new, expensive toy on their favourite objects, be that a remote galaxy at the dawn of time, a planet-spawning circumstellar disc, an exoplanet’s atmosphere, or a denizen of our own outer Solar System.

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Artist’s impression of the James Webb Space Telescope. Credit: ESA, NASA, S. Beckwith (STScI) and the HUDF Team, Northrop Grumman Aerospace Systems / STScI / ATG medialab

James Webb Space Telescope has less pointing flexibility than the Hubble Space Telescope.

Since the telescope must face away from the Sun to keep its instruments consistently cool, its ‘field of regard’ will cover 40% of the sky on any given day, and it will take around 6 months to access the whole of the sky.

JWST’s mid-course corrections used up less fuel than expected, which means there’s more left to keep the space telescope in its L2 orbit.

As a result, its operational lifetime may be extended beyond the projected operational period of 10 years.

How the James Webb Space Telescope unfolded in space

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The James Webb Space Telescope’s 10 stages of deployment. Credit: NASA’s Goddard Space Flight Center.

It took more than 50 individual steps and two weeks to for JWST to reach its orbital point and become fully deployed.

Here’s a timeline of how it all took place.

  1. 25 December 2021, 12:20 UT: JWST launches from the Guiana Space Centre on an Ariane 5 rocket; after 27 minutes, it separates from the launcher’s upper stage to travel to L2 alone.
  2. 25 December 2021, 12:48 UT Deployment of JWST’s 6m, five-panel solar array, which delivers about 1Kw of power. The telescope can now switch from battery power to its own power.
  3. 26 December 2021: Deployment of the high-gain communications antenna, which allows communication with Earth through NASA’s Deep Space Network.
  4. 28 December 2021: The Forward Unitized Pallet Structure (UPS), which supports and contains the five folded layers forming the front half of the sunshield, is lowered into place.
  5. 29 December 2021: The Deployable Tower Assembly (DTA) is raised by 1.2m for better thermal isolation and to give room for the sunshield to unfold in front and behind.
  6. 30–31 December 2021: Sunshield mid-booms are extended on either side, pulling the folded sunshield layers with them, to form the first part of its distinctive 21m x 14m kite shape.
  7. 3–4 January 2022: The five Kapton layers of Webb’s sunshield are tensioned. While the Sun-facing side endures temperatures up to 90°C, the shielded side will be as cold as –230°C.
  8. 5 January 2022: JWST’s 74cm convex secondary mirror  is deployed. The foldable structure supporting it has been dubbed “the world’s most sophisticated tripod”.
  9. 6 January 2022: Deployment of the 1.2m x 2.4m Aft Deployable Instrument Radiator (ADIR), which radiates heat from the space telescope’s science instruments into space.
  10. 7–8 January 2022: Deployment of the two side panels forming JWST’s 6.5m primary mirror. Its 18 hexagonal segments are made of lightweight beryllium coated with pure gold.

This article originally appeared in the March 2022 issue of BBC Sky at Night Magazine.