Where is James Webb now?
Good news from the Telescope
The James Webb Space Telescope has lifted off.
After three postponements in the last ten days and more than two decades of waiting,
on December 25, at 12:20 p.m. Universal Time, the largest and most complex space telescope
ever built lifted off the launch pad in Kourou, French Guiana, propelled beyond the atmosphere
by a powerful and reliable Ariane 5 rocket.
At this moment it is already on its way to its operational destination, the Lagrangian
point L2, 1.5 million kilometers from Earth, and when you guys listen to these words of
mine, probably the first days of January, Webb will have already completed the deployment
of the big sunshield, one of the most complex and dangerous operations.
The Webb Telescope, in fact, has passed unscathed the Russian roulette of the launch, but in
front of him still has a long journey full of pitfalls, which in the next six months
could endanger the success of the mission at any stage.
It is incalculable the number of times we have talked about the infamous James Webb
Space Telescope: its birth and development have been incredibly troubled and it took
more than ten years to bring it to completion.
These problems have been discussed enough, but now - as many of you know - it is right
to give space to the good news: the Webb Telescope has started!
A wonderful Christmas present for the many fans of space and astronomy!
And not only that...
On December 29, the day Webb also passed the Moon's orbit, NASA announced that Ariane had
performed so well during launch that the telescope now has much more fuel available than we'd
hoped for...
In fact, Ariane was so precise in drawing Webb's trajectory to the Lagrangian L2 point
that further future course corrections are unnecessary.
The fuel on board the telescope is a surplus compared to the operational autonomy guaranteed
by the solar panels, but its excess availability will allow useful operations to ensure the
survival of the project for longer, deeper, and more ambitious studies than the team could
not hope for before the Christmas launch.
Before, a duration of 5 years was prudently assumed, now we have moved to 10 or 15 years!
A huge step forward!
The idea of sending such a large telescope into space began to circulate among astronomers
and NASA in the 1990s, shortly after the launch of the Hubble Space Telescope, which in a
30-year career has made countless observations and discoveries about stars, galaxies, nebulae,
and black holes.
Hubble was the best demonstration of the possibility of building an observatory in orbit, excluding
the distortions caused by the Earth's atmosphere that often complicate life for telescopes
here
on Earth.
If it was possible to do this with an instrument equipped with a 2.4-meter diameter mirror,
then there was a good chance that even larger telescopes could be built and taken into orbit,
astronomers and engineers thought.
So much so that a committee was set up to explore the possibility of building a large,
next-generation telescope, capable of observing celestial bodies billions of light-years away,
among the first to take shape during the turbulent formation of the Universe some 13.8 billion
years ago.
Early proposals were for a telescope with a diameter of 4 meters, slightly less than
twice the size of Hubble, and with instruments calibrated to make infrared observations.
The whole initiative would have cost about a billion dollars and would have required
a relatively short time to be realized.
At least that's what was thought...
The administrator of NASA, Dan Goldin, expressed the interest of the U.S. space agency for
the project, and even said that the thing would make sense only by making a telescope
with a much larger mirror, 8 meters in diameter!
It’s kind of what’s going on nowadays with the LUVOIR Space Telescope project, which
is not yet known if it will be 8 or 15 meters in diameter!
The announcement was greeted with great interest by the astronomical community, but it was
also the starting point of one of the most difficult, troubled, and expensive projects
in recent NASA history.
The very ambitious plan was later revised, arriving at the compromise of a mirror of
6.5 meters that would not be possible to bring into orbit already open, because of the space
offered by any rocket.
It was, therefore, necessary to think of a system never experienced before and that,
together with other changes to the project, determined a considerable increase in the
cost of implementation.
The delivery date was postponed several times due to technical problems, mostly due to the
need to develop completely new and unexplored technological solutions.
NASA assumed to have Webb ready for the end of 2011 spending a total of about 5 billion
dollars, but the delays accumulated, so that at some point the U.S. Congress considered
the possibility of stopping the project, but it was now too advanced to be stopped.
In the end, 25 years were needed to design and finish the telescope, with an expenditure
of more than 10 billion dollars.
That seems a lot, but nothing compared to the 2000 billion dollars that only in 2020
were spent in the world for armaments ... What do you guys think?
Ok, let us put the controversy aside and return to the news these days.
It seems that after the launch, everything is going as the most optimistic forecasts
expected.
The flow of data between the control center and the telescope has already begun and in
the meantime, the solar panels have been deployed according to schedule and has also begun the
more complex deployment of the sunshield.
And now, what happens?
"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!"
The next step will be to allow the full deployment of the sunshield.
A very complicated and delicate process ... in which 140 release mechanisms, 70 hinges, 400
rollers, 90 cables, and eight motors must interlock and all function properly.
The last step to installing the parasol will be to correctly tensify its five membranes.
If nothing goes wrong, about 12-13 days after launch, on January 6 or 7, the wings on both
sides of the mirror will extend and lock into place, creating a full-size surface.
All segments of primary and secondary mirrors will be unlocked and their mobility controlled.
The secondary mirror of the telescope, placed at the end of three long arms, is lowered
in position.
Despite its name, the secondary mirror is a critical component to Webb’s success.
If other parts of the telescope do not work perfectly, there may be solutions, but if
the secondary mirror is not deployed successfully there will be nothing more to do...
Towards the end of the first month of the mission, the final intermediate maneuver will
take place to reach the optimum orbit around L2.
This maneuver, as NASA has announced, will perhaps not be necessary.
During this period, the scientific instruments onboard will also be activated.
The remaining five months of commissioning will focus on optical alignment and calibration
of the coronograph instruments, spectrograph, and imaging chambers.
A month after launch, Webb should finally reach L2, completing one of the boldest space
flights ever and allowing astronomers around the world to breathe a collective sigh of
relief.
In the second, third, and fourth months, Webb will attempt to point a single bright star
and demonstrate that the observatory can acquire and engage targets.
But since the segments of the primary mirror have yet to be aligned to function as a single
mirror, up to 18 distinct images of the same star will occur on the focal plane.
The process of aligning the individual mirrors will last at least a couple of months and
will end only when each of them focuses the image of the star in a single point.
In the fifth and sixth months, all the operating modes of scientific instruments will be meticulously
calibrated, observing representative targets, and the ability to follow 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 his scientific mission and begin conducting routine scientific
operations.
Five more months or so will be devoted to early release scientific observations.
Selected astronomers will train the telescope on a wide range of targets, from distant galaxies
to planets in our solar system, to gain experience with the features of this new instrument and
share that knowledge with the rest of the astronomical community.
Other astronomers will take precedence over so-called "time-guaranteed observatories",
people who have spent years of their lives designing and building this telescope and
will therefore have the first opportunity to use it without having to compete for observation
time.
Webb is essentially an infrared telescope, a space observatory that will play a key role
in various areas of astronomical research in the near future.
But what exactly does "infrared astronomy" mean?
Quite simply, it means that Webb will be able to see beyond the visible spectrum, at wavelengths
of light longer than those to which our eyes are accustomed.
The advantage?
To take a trivial example: If the sky near the horizon appears red to us at sunset and
sunrise, it's only because the infrared light, with its long separation, can more easily
scan the dust grains in the lower atmosphere and then reach our eyes to a greater extent
than light of shorter wavelengths.
Similarly, the James Webb Space Telescope will be able to reveal what's happening inside
clusters of gas and dust that are opaque to visible light and therefore inaccessible even
to large optical telescopes from the ground.
In addition, for a variety of reasons, the light from the most distant objects undergoes
a "stretching" effect toward the red, causing the light itself to move from the visible
to the infrared.
This means that observing these very distant objects, such as the first galaxies to form
in the universe, requires a telescope that specializes in infrared observation, such
as the Webb.
To see infrared light, however, the Webb must shield both the heat of the Sun and that of
its own instruments.
The first line of defense is a five-layer solar shield that will keep the telescope
cool at -233 degrees Celsius.
But even a solar shield isn't enough: Webb must also avoid thermal interference from
Earth and the Moon.
That explains why the telescope is flying into a small region of space called L2, which
is 1.5 million kilometers from Earth and 1.1 million kilometers from the Moon.
There, the Sun's and Earth's gravity balance each other in a way that allows Webb to keep
the Sun, Earth, and Moon permanently behind the sunshield while he observes the cosmos
ahead.
The problem with this solution is that there's no way to intervene in the telescope if problems
arise.
No manned spacecraft could reach it, except for the wonders of SpaceX with its revolutionary
Starship.
In recent years, Hubble has been able to identify galaxies formed just 400 million years after
the Big Bang.
NASA and other research organizations hope we can reach 100 million years with the new
telescope.
Observing galaxies that old could be the way to understand how today's galaxies formed
and why they've supermassive black holes at their centers, that's, with masses billions
of times that of our Sun.
Webb can also be used to determine more precisely the rate at which the universe is expanding.
The problem has been discussed for years, it seems to be almost solved thanks to the
data collected by Hubble, and not only that, other elements have emerged that have challenged
some of the original assumptions.
The determination of the expansion rate is essential to correctly calculate the distance
between galaxies and, more generally, the evolution of the universe.
But there's something else that the James Webb telescope can help us explore, in an
area of astronomy that was fringe when construction began and is now one of the most interesting
and vibrant: the exploration and especially the study of the atmospheres of extrasolar
planets!
For millennia, mankind has pondered the questions: "Are we alone?
What's life?
Is there life elsewhere that's similar to us?", and today, for the first time, we have
the scientific knowledge and technological capabilities to realistically begin to find
the answers to these questions.
Webb will be able to directly detect many new planets, especially in the gas giant category,
but most importantly, the hope is that its extraordinary spectrographs will be able to
probe the atmospheres of Earth-like planets located in what's known as the Habitability
Belt.
The telescope is equipped with a coronagraph that allows direct imaging of planets near
very bright stars.
The planet will appear as a bright, seemingly insignificant dot.
In fact, we can derive very important information from this point using spectroscopy: Even if
an exoplanet appears as just a single pixel, that point of light would change in important
ways over time.
With enough data, we could determine how fast the planet rotates on its axis, whether it's
fully or partially cloudy and how those clouds are composed, whether there are fluids, continents,
and oceans and what portion of them is covered with water, whether there are polar ice caps,
and whether the colors of the continents change with the seasons.
By observing the planet as it moves along its star's disk, Webb will also be able to
look for chemical biomarkers in the atmosphere such as oxygen, ozone, and methane - possible
indicators of the presence of at least elemental life.
In short, with Webb, the prospects for a future full of surprises are incredibly exciting.
A quarter-century ago, the existence of exoplanets was a subject for science fiction movies,
and today we know of nearly 5,000.
And to know that a powerful space machine sent by us Earthlings is about to answer the
question that most troubles our hearts...
well, that's a thought that warms our existence and makes it seem better.
Isn't that right, folks?
Oh, by the way... if you want to follow Webb's astrodynamic situation (position, distance,
velocity, etc.) step by step, all you've to do is visit this page: https://webb.nasa.gov/content/webbLaunch/whereIsWebb.html
See you soon!