khoji parkSpace · Baltimore, Maryland · 2022
The Telescope Had to Unfold After It Left Earth
NASA's infrared observatory completes deployment and releases its first high-resolution images.
Read in slides1. Folded for Launch
The James Webb Space Telescope left French Guiana on an Ariane 5 rocket on December 25, 2021. Its mirror and sunshield had been folded to fit inside the rocket. Once separated, the observatory had to open those structures during its journey away from Earth before it could begin its planned observations.
The rocket delivered it to space with the deployment sequence still ahead.
2. Power and Contact
The solar array deployed after separation, giving Webb a source of electrical power. Other early operations established communications and adjusted its course toward an orbit around the Sun–Earth L2 region. Controllers monitored the spacecraft while preparing commands for the larger structures, whose folded parts still occupied their launch positions.
The sunshield required a sequence of releases and extensions.
3. Five Layers
Controllers deployed the structures holding Webb’s five-layer sunshield, spread the membranes and tensioned the individual layers. The shield separated the hot, Sun-facing side from the cold telescope instruments. On January 4, 2022, the team completed tensioning the final layer. The observatory’s largest shield deployment was complete, but its mirrors still needed to open.
The next operations would put the mirrors into their observing arrangement.
4. Opening the Mirror
The secondary mirror’s support structure moved into position. The two folded wings of the primary mirror then opened and locked, with the final wing completing its movement on January 8. Webb now had its major structures deployed. The eighteen primary-mirror segments still needed careful adjustment before their light could form a single focused image.
Opening the telescope was different from aligning it.
5. Reaching the Operating Orbit
On January 24, Webb fired its thrusters to enter its planned orbit around the Sun–Earth L2 region, about 1.5 million kilometres from Earth. It had reached the destination while cooling and commissioning continued. The team could now concentrate on bringing the deployed mirrors and instruments into the condition required for science observations.
A star became the target for checking the separated mirror images.
6. Eighteen Images to One
Using a bright star, engineers identified the light collected by each mirror segment. They adjusted the segments through successive alignment stages so that the separate images could be brought together. The actuators changed the mirrors’ positions in very small steps. Testing then extended across Webb’s instruments rather than ending with a single camera image.
Cooling and instrument checks continued after the mirrors were aligned.
7. The First Public View
On July 11, 2022, a Webb deep-field image was presented at the White House. It showed the galaxy cluster SMACS 0723 and more distant galaxies whose light was magnified by the cluster’s gravity. The next day’s release would include other targets and a spectrum, following months of deployment, cooling and commissioning.
The wider first-science release followed on July 12.
8. From Folded Hardware to Data
NASA, ESA and the Canadian Space Agency released Webb’s first set of full-color science images and spectra in July 2022 after deployment, cooling and alignment. The initial deep-field image had been shown on July 11, with the wider release on July 12. The folded observatory had reached its operating location and completed commissioning before the published science observations began.
The deployments and alignment led to the first science release.