The joint NASA/ESA/CSA James Webb Space Telescope (JWST) has successfully inserted itself into its orbit at the Earth-Sun Lagrange Point 2 (L2), doing so at 2:05 pm EST (19:05 UTC) on January 24, 2022. The insertion into L2 orbit signifies the end of the observatory’s immensely complex deployment process and the beginning of the telescope’s commissioning activities.
The orbit insertion maneuver began at 2pm EST (19:00 UTC), lasted for five minutes, and added 1.6 meters per second velocity to Webb to send it into its proper orbit.
Before the insertion, which occurred at T+29 days from launch, JWST had to perform a series of complex deployments to get into its final configuration for deep space observations. The entire deployment sequence consisted of 344 unfolds, which saw the observatory unfurl from its launch position. Of those unfolds, 307 (87%) were single-point failure areas — meaning if any of those 307 unfolds had failed, the entire mission would be lost.
But every single one of those 344 highly complex unfolds worked. Additionally, the completion of JWST’s L2 insertion burn marked the end of the telescope’s mid-course correction burns — all three of which were completed successfully.
JWST’s journey to L2 began on December 25, 2021, when the observatory launched atop an Arianespace Ariane 5 rocket from pad ELA-3 at the Guiana Space Centre in Kourou, French Guiana. JWST separated from the Ariane 5 upper stage at T+27 minutes on a trajectory to L2.
The trajectory Ariane 5 placed James Webb on was accurate enough to minimize the amount of fuel the observatory needed for its trip to L2, allowing JWST to have enough fuel for around 20 years — 10 years more than originally expected — of scientific operations.
In the seconds following separation, JWST deployed its solar array, allowing the observatory to begin producing power. The first of Webb’s three planned mid-course correction burns took place 12 hours later, allowing the observatory to correct for the minor mistakes in its trajectory that remained from launch. The solar array deployment and first mid-course correction burn were the only time-critical steps in James Webb’s deployment sequence.
The next day saw the final autonomous deployments with the Gimballed Antenna Assembly (GAA) — which will allow the observatory to communicate and transfer data from L2 to ground stations on Earth. The second of three mid-course correction burns was also performed on T+2 days.
Three days after launch saw the beginning of the deployment sequence of the sunshield — one of the critically important components on the entire observatory. The forward and aft Unitized Pallet Structures were also deployed, marking the beginning of all major deployments.
The following day, the Deployable Tower Assembly (DTA) unfolded, lifting the mirror away from the sunshield to give room to the sunshield membranes to deploy.
T+5 days then saw the Aft Momentum Flap deploy from the aft UPS pallet. The Aft Momentum Flap offsets the amount of solar pressure that affects the observatory, minimizing fuel usage. Furthermore, T+5 days also marked the retraction of the sunshield covers.
The following day came the true test of JWST’s deployment sequence — sunshield mid-boom unfurling that pulled the entire sunshield out for tensioning.
This is it: we’ve just wrapped up one of the most challenging steps of our journey to #UnfoldTheUniverse.
With all five layers of sunshield tensioning complete, about 75% of our 344 single-point failures have been retired! pic.twitter.com/P9jJhu7bJX
— NASA Webb Telescope (@NASAWebb) January 4, 2022
The mid-booms and sunshield successfully deployed, leaving one critical step in the sequence: tensioning of the five sunshield membrane layers. The entire membrane tensioning process lasted two days as teams worked to individually and carefully tension each of the five fragile sunshield layers.
As planned, all five membranes were successfully deployed, marking the end of the sunshield deployment process and the beginning of James Webb’s initial cooling period.
However, one vital system had yet to deploy — the mirror and observatory optics.
The deployments of JWST’s Secondary Mirror Support Structure (SMSS) and the secondary mirror were completed on T+10 days, following which the Aft Deployed Instrument Radiator (ADIR) was successfully released from its launch position.
On T+12 days, primary mirror deployments began. This involved rotating the port and starboard mirror wings into place from their launch positions and latching them to the primary mirror structure. The port primary mirror wing was deployed and latched into place first.
The next day, the starboard primary mirror wing successfully rotated and latched into its final operational position, signifying the end of all major deployments on Webb and marking the successful deployment of all observatory systems — a major achievement more than two decades in the making.
But the observatory’s journey was not yet complete. It still needed to finish its transfer to L2 and move each of its 18 individual primary mirror segments out of their launch position to ready them for the alignment process.
JWST’s mirror system is the most complex ever flown into space. The primary mirror consists of 18 individual mirrors that each feature a small motor to allow each segment to move into a position that allows them to efficiently bounce light onto the secondary mirror — which then bounces light into the tertiary mirror which then carries the light to the instruments.
However, due to the nature of launch and how the telescope needed to fold, each of the 18 mirrors could not launch in their operational positions — which means they now have to be aligned with each other to “focus” the overall primary mirror.
In the days following completion of the observatory’s main deployment sequence, the JWST mirror team moved each of the 18 mirror segments to ensure each mirror’s motor successfully made it through launch and deployment and confirming that the team can perform the months-long alignment process following insertion at L2.
At this point, the final step in the deployment sequence of Webb was the telescope’s insertion into L2.
So…you’ve heard that the Webb telescope will be orbiting Lagrange point 2. But what even is that, anyway? And how do you orbit something that isn’t an object?
— NASA Webb Telescope (@NASAWebb) January 21, 2022
However, even though JWST is now in orbit of the L2 point, it is still not ready to begin observing the universe. The telescope still has nearly five months of commissioning before science teams from around the world can begin using the observatory for groundbreaking astrophysics research.
Throughout the next five months, JWST teams will continue bringing the observatory online and slowly testing its various systems while the mirror team aligns and focuses the telescope for observations.
Furthermore, observatory teams will continue to monitor the temperature of the telescope while the sunshield and cryocooler bring the array’s temperature down to the needed 6 Kelvin for the sensitive Infrared observations Webb is tasked with performing.
Currently, the first images from JWST are expected in mid-2022, assuming no errors or delays occur during the observatory’s commissioning phase.
(Lead image: Artist’s rendering of the James Webb Space Telescope fully deployed in space. Credit: NASA/GSFC/CIL/Adriana Manrique Gutierrez)
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