The James Webb Telescope is about to launch: the first 30 days will be pure terror.
Do you remember the opening scene of the first Star Wars, which announced "Long ago, in a
distant, distant galaxy..." as it slowly flowed towards an infinite perspective?
Well, it is in the same way that you should imagine to see these other words flowing:
"The James Webb Space Telescope, also called Webb or JWST, is a large, space-based observatory,
optimized for infrared wavelengths, which will complement and extend the discoveries
of the Hubble Space Telescope.
At its peak, as many as 2,000 scientists and technicians were working on Webb, with a total
of about 10,000 people involved in its construction over the decades.
It will have longer wavelength coverage and greatly improved sensitivity.
The longer wavelengths enable Webb to look further back in time to find the first galaxies
that formed in the early Universe, and to peer inside dust clouds where stars and planetary
systems are forming today..."
The reason for my strange request?
Well... in my opinion, the adventure that is about to begin with the launch of the Webb
Telescope will probably be as exciting and full of twists and turns as the Star Wars
saga.
With a single, great initial fear: that something could go wrong at the start or in the first
and very complicated month of the mission.
Let's see together why.
The first big news is that in these days has been confirmed the date of December 18 for
the launch.
So, no more delays (and no more change of name, as some devotee of the "cancel culture"
wanted): this time we start for real, and the James Webb Space Telescope will finally
leave Earth on a mission to revolutionize astrophysics and cosmology!
The second good news is that the instrument has already arrived at its destination, after
a very long transport by sea.
The telescope arrived successfully in French Guiana on October 13, after a 16-day trip
to the ocean, kept secret to avoid tempting pirates.
From the port of arrival, the telescope then made a short journey on land to the ESA spaceport
in Kourou.
JWST is now at the payload processing facility, where staff will start the process of getting
the telescope into the Ariane 5 rocket fairing.
The telescope was shipped in a specially built French vessel named the MN Colibri, designed
to transport aerospace components, with the telescope inside a water-tight chamber.
A specialized freight company oversaw the transport, beginning with moving the container
and telescope from Northrup Grumman's facilities, through Southern California's freeway system
to the ship, docked by Huntington Beach, CA.
The massive clean air chamber was built so the telescope would not be exposed to vibrations,
any excessive G forces of acceleration and deceleration, the rolling or pitching on the
water due to sea swell or wind, or excessive temperatures.
The 9,300 km sea voyage took Webb from California through the Panama Canal to Port de Pariacabo
on the Kourou River in French Guiana, on the northeastern coast of South America.
A crossing that was also the last major terrestrial voyage of the James Webb Space Telescope.
In fact, its assembly began in 2013 in Maryland, then continued in Texas in 2017 with cryogenic
testing, and finally in California in 2018.
The Goddard Space Flight Center was its home until September 24, the day it was transported
to the port to be boarded and transported by ship.
The next two months will see the performance of some tests, to verify that the transport
has not caused damage, but above all will proceed to the complex integration of the
telescope in the Ariane 5 rocket.
The whole project of the Webb Telescope was in fact born around the specifications of
the launcher, whose capacity and load size were one of the first constraints of the engineers!
Inside the launcher, the available volume has a diameter of 4.6 for a height of 16.2
meters.
And all measurements, both of the cargo bay and the telescope were calculated to the centimeter
to accommodate the instrument folded on itself "like origami"
When it is a week before launch, the telescope will be placed on the rocket and 6 days before
launch the two fairings will be positioned.
Finally, the day before launch, Ariane 5 will be positioned on the pad.
OK.
As an old Beatles song said, it has been a long and winding road that after decades of
planning, work, delays, and cost overruns has brought the Webb Telescope up to the space
base of Kourou, finally ready for launch.
But even now that the mythological instrument is about to be embarked in the spacious hold
of the Ariane, no one among NASA technicians flaunts optimism or you already feel the victory
in your pocket...
All the people involved in the project know perfectly well that everything that has been
done so far could be lost in an instant... both during the launch and in any of the countless
other procedures that the Webb telescope will have to overcome to get to the Lagrangian
point L2, 1.5 million kilometers from Earth.
You know it, don't you?
Those who organize missions to Mars almost boast of the famous "seven minutes of terror"
that each ship sent to the red planet makes those who follow it from Earth, but with the
Webb telescope there is no comparison ... the seven minutes will become thirty days!
A whole month of suffering, spent praying that a million things that could go wrong
would instead go straight...
About 50 deployments, in fact, need to occur after launch to set up the huge system.
With 344 so-called single-point failures-individual steps that have to work for the mission to
be a success-this deployment after launch will keep us on edge for three weeks or so.
We can't describe all of the 344 traps scattered along the road that the Webb telescope will
travel, but the most important and dangerous will surely be these:
Presuming no further delays in its path to the launchpad, early in the morning of December
18, Webb will blast off with a slight eastward trajectory over the Atlantic Ocean.
Its Ariane 5 rocket is considered a reliable workhorse, and the telescope itself has passed
tests meant to mimic the stresses of a launch, so confidence is high that the journey to
orbit will go smoothly.
The launch vehicle will provide thrust for roughly 26 minutes after liftoff.
Moments after the second stage engine cut-off, Webb will separate from the Ariane, which
will trigger the solar array to deploy within minutes so that Webb can start making electricity
from sunshine and stop draining its battery.
Webb will quickly establish its ability to orient itself and “fly” in space.
Although the solar array deployment is a relatively simple procedure, its success is critical
to power all following operations.
About 12 hours after launch, the craft’s thrusters will fire for the first time to
correct its trajectory.
Course corrections must be efficient to preserve the telescope’s fuel and maximize its life
span.
Confirmation of a successful course correction will not arrive until well after the fact,
although subsequent tweaks to Webb’s flight trajectory can be made if needed.
"Hey, guys, just a moment before we continue...
BE sure to join the Insane Curiosity Channel...
Click on the bell, you will help us to make products of ever-higher quality!"
As the telescope nears its third day in space, Webb will begin to deploy one of its most
intricate and prominent instruments: the sunshield.
If unspooled without a hitch, a stack of five enormous kite-shaped sheets of polyimide film
will block sunlight and heat from reaching the telescope’s infrared sensors, which
must remain at extremely low cryogenic temperatures to function properly.
The sunshield is crucial for keeping the telescope sufficiently cold, but to open it around 150
release mechanisms must fire correctly over three days.
The complicated deployment involves around 7,000 parts, including 400 pulleys, eight
motors, and 140 release actuators.
The sunshield’s deployment is key to achieving scientists’ wildest dreams for the observatory.
But for aerospace engineers, the procedure’s complexity and the high number of single-point
failures are the stuff of nightmares.
In fact, it will be a real challenge to ensure that these five extremely thin layers, more
than twenty meters long, unfold perfectly, keeping the right separation from each other.
And the anxiety will not fade with a nominal sunshield deployment.
The next step will be the separation between the spacecraft bus and telescope by extending
the telescoping tower between them.
The tower will extend about two meters, and it is necessary at this point in the sequence
so that the rest of the sunshield deployment can proceed.
Next, the sunshield membranes will be unpinned and the telescoping sunshield midbooms will
extend – first the port side and then the starboard side – pulling the membranes out
with them.
The last sunshield deployment step is tensioning of the membranes.
In the meantime, other things like radiators will be released and deployed.
During the second week after launch will finish deploying the telescope structures by unfolding
and latching the secondary mirror tripod and rotating and latching the two primary mirror
wings.
Note that the telescope and scientific instruments will start to cool rapidly in the shade of
the sunshield, but it will take several weeks for them to cool all the way down and reach
stable temperatures.
This cooldown will be carefully controlled with strategically-placed electric heater
strips so that everything shrinks carefully and so that water trapped inside parts of
the observatory can escape as gas to the vacuum of space and not freeze as ice onto mirrors
or detectors, which would degrade scientific performance.
All segments of the primary and secondary mirrors will be unlocked and their mobility
will be verified.
The telescope’s secondary mirror, positioned at the end of three long arms, will lower
into place.
Despite its name, the secondary mirror is a critical component for Webb’s success.
If other deployments do not work out perfectly, there may be work-arounds, but if the secondary
mirror doesn’t deploy successfully, "we have no telescope, we got nothing.”
Near the end of the first month of the mission, there will be the last mid-course maneuver
to insert into the optimum orbit around L2.
During this time, will also power up the scientific instrument systems.
The remaining five months of commissioning will be all about aligning the optics and
calibrating the scientific instruments.
Finally, a month after launch, Webb should reach L2, concluding one of the most audacious
spaceflights ever attempted and allowing the world’s astronomers to collectively exhale.
In the second, third, and fourth months, Webb will try to point at a single bright star
and demonstrate that the observatory can acquire and lock onto targets.
But because the primary mirror segments have yet to be aligned to work as a single mirror,
there will be up to 18 distorted images of the same single target star.
The long alignment process of all telescope optics will then be initiated, beginning with
identifying which primary mirror segment goes with which image by moving each segment one
at a time and ending a few months later with all the segments aligned as one and the secondary
mirror aligned optimally.
In the fifth and sixth months, all the operating modes of scientific instruments will be meticulously
calibrated, observing representative targets, and the ability to track moving targets such
as asteroids, comets, moons, and planets in our solar system will be established.
This will be followed by a phase called "Early Release Observations", which will illustrate
the imaging capabilities of the observatory.
After six months, Webb will begin its science mission and start to conduct routine science
operations.
Another five months or so will be dedicated to early release science observations.
Select astronomers will train the telescope on a wide range of targets, from distant galaxies
to planets in our own solar system, to gain experience with the nuances of this new instrument
and share that knowledge with the rest of the astronomical community—somewhat like
Air Force test pilots wringing out a new fighter jet before it gets deployed to flight squadrons.
Other early users will be the so-called “guaranteed time observers,” people who have spent years
of their lives planning and building this new telescope and so will get the first crack
at using it, without having to compete for observing time.
The JWST was designed primarily for deep-space cosmology, but any telescope of this caliber
does a little bit of everything, and it will be called on to do virtually every kind of
astronomical observation—whenever and wherever its unique sensitivity and power is required.
OK, guys, that's it for now.
If in mid-January 2022 the telescope will be in position at the L2 point and fully operational,
then a long period of incredible satisfaction will open for all of us.
And maybe the universe will decide to reveal some of its mysteries to us!