Well now, after decades of anticipation of the James Webb Space Telescope and the
science it’s going to provide, we have so far a truly picture perfect mission,
and even some initial images that are rather breathtaking. In other words,
this telescope works. For those joining this story now, this mission took decades to make a reality.
Budget overruns, issues ranging far and wide, and political concerns created all sorts of problems
that plagued this project but when it finally came time to launch, oh launch it did indeed.
To recap, the launch was basically perfect. The venerable Ariane 5 rocket that lofted JWST into
space performed about as well as it realistically could have, preserving its unusually solid track
record for accurate launches and saving the JWST a good deal of fuel for its primary mission,
indeed extending it significantly. We’re going to have this telescope for a good
long while for observations, exceeding a decade, and who knows by how much since
there are further ways to conserve fuel during observations and keep it going even longer.
JWST then unfolded itself in an unprecedented magnificent feat of engineering without any major
problems. This was quite an accomplishment, since the telescope had to be launched folded so that it
would fit in the payload fairing of the Ariane 5, which is one of the largest in the industry,
but still limited. This created a situation where the telescope had hundreds of potential
failure points and a whole lot of moving parts. But NASA and its contractors are used to this,
and often deal with high numbers of potential failure points, but not often as many as JWST had.
And there wasn’t a single failure in the launch and deployment of the telescope.
The telescope then began its month-long journey to L2. Here it’s worth explaining just what
lagrange points are, and why they are useful for spacecraft. These are special points in space
located between gravitational objects that give an advantage if you want to keep a spacecraft in
a certain position and conserve fuel by minimizing the amount of fuel spent keeping it in position.
This is due to gravity from the objects acting on the spacecraft, creating an advantage.
There are five lagrange points, some stable, some not. The unstable ones are known as L1,
L2 and L3. The stable ones are L4 and L5. Most are useful. L1 is where the solar observatory SOHO
sits because it provides a full uninterrupted view of the sun. L2 is where James Webb is now located,
and the reason for that is that it’s easy to communicate with probes at this point,
and it offers an uninterrupted view of the cosmos, keeping the sun, earth and moon behind it,
and allows uninterrupted sun exposure for power. But that it’s one of the unstable points,
JWST still must expend fuel to stay in position and also to counter the effects of radiation
pressure from the sun, remember JWST’s sun shield has a lot of area, and thus acts as a light sail.
L3 is a point we never use because it’s always behind the sun.
L4 and L5, being stable, allow for orbits. At these Jupiter-Sun lagrange points for example,
you find the trojan asteroids that have accumulated there. In short,
L2 was the best place to locate JWST from a fuel consumption and observation point of view.
All while this was happening, JWST was going through another very important step
that there was no way to speed up. It had to cool down to operational temperatures after the launch.
This took a while, the telescope essentially is hot on the sun side, cold on the telescope side,
which is why it has multiple sheets in its sun shade, to allow for the temperature extremes
of the two sides of the spacecraft. Currently those extremes are 128 degrees fahrenheit on
the sun side and negative 393 on the cold side, or 53 and -236 celsius respectively.
After reaching L2 and fully deploying came the process of aligning the individual mirror segments
of the telescope. Interestingly, there was actually a contingency plan in place that if the
two ears of the mirror didn’t properly deploy, the remaining core mirrors could actually have been
used as a telescope and wouldn’t have been a total loss, rather it would have simply been operating
at reduced function. That did not happen, and both deployed normally, completing the telescope.
But aligning mirrors is a necessary process. The telescope's launch and deployment wouldn’t
have allowed for a pre-alignment, so it had to be done in space, the power of a rocket launch
isn’t good for holding a precision alignment. This was accomplished by tiny motors that move
the mirrors into position that work very, very slowly, not unlike the rate at which grass grows,
so the process took several weeks. Two test images were taken during this process,
one before alignment that shows all the individual mirrors looking at a star,
but not all aligned together creating multiple images. In this image, you can see multiple stars,
but they’re actually all the same star, just with the mirrors all slightly off from each other.
The star in the image is HD 84406, a type G star, which is the same class as the sun but this one
is more massive. The star was chosen because it’s relatively isolated in the field of view.
After alignment came the first focused image from the James Webb Space Telescope
and what an image it is. You can see in this photo the star 2MASS J17554042+6551277 in crisp focus,
with a backdrop of individual galaxies and stars. This also tells us that the mirrors
are ground correctly. This was a problem for the Hubble Space Telescope which had an improperly
curved mirror that wasn’t discovered until it was in space, which had to be fixed with
a space shuttle servicing mission to install corrective optics so the telescope could focus.
The ongoing next step now is activating the telescope's instrumentation and cameras and
calibrating them. With any luck, JWST will begin observations sometime around summer. So
the natural question is, now that we have JWST up and running, what’s the next space telescope going
to look like? The story is actually rather odd and very different from that of JWST.
This telescope wasn’t actually designed to be an astronomical telescope at all.
Rather, it was supposed to be part of a top secret spy satellite. Repurposed as s a space telescope
it was initially known as the WFIRST project, but has since been renamed the Nancy Grace
Roman Space Telescope. Nancy Grace Roman was an astronomer that worked in stellar classification,
and she was NASA’s astronomy chief in the 60’s and 70’s, but she was also instrumental in the
realization of the Hubble Space Telescope, to the point of often being called the Mother of Hubble.
It’s fitting indeed that a successor to Hubble will bear her name.
The telescope’s primary mirror is 2.4 meters, which is the size of the Hubble Space telescope,
but less than James Webb’s 6.5 meters. Its instrumentation package has a wide field
camera that can handle visible and near-infrared light much like Hubble
and a smaller field of view camera with a spectrometer that also covers visible and
near-infrared wavelengths. The telescope’s launch date as of right now, will be in May of 2027.
So how does a modern space telescope have its origins as a spy satellite?
Cue in the National Reconnaissance Office, or NRO of the US government. In short, they had planned
spy satellites with very large mirrors designed to look at earth for clandestine purposes. Two
mirrors were not used and the NRO basically had two Hubble telescope mirrors sitting around,
but having a shorter focal length, they would provide a wider field of view than Hubble.
They eventually donated the mirrors to NASA,
essentially not wanting them to go to waste. But there was a catch.
Because of the origins of these mirrors, one condition is that the telescope must
never under any circumstances look at earth. Presumably because NASA’s imagery is public,
and someone might be able to work out the capabilities and resolution of existing telescope
based spy satellites, though I would think you could do that anyway from knowing the specs.
The Roman Telescope research objectives are wide ranging. One is to specifically try to probe dark
energy and the expansion of the universe in conjunction with the European Space Agency’s
EUCLID mission. Dark energy is strange because it either exists and is driving the accelerated
expansion of the universe, or there is something very wrong with General Relativity. We may find
out which it is from these missions, and if it actually is a form of energy then questions can be
asked and probed about whether this acceleration has been constant, or has evolved somehow.
The telescope will also study exoplanets and their habitability, specifically help fill out
the picture of just how common solar systems similar to ours actually are, this is actually
a pretty weighty question since what we’ve seen so far is that our solar system is not normal, and no
analogue of it has yet been found. This is where gravitational microlensing comes into play, the
idea is that by using it, you can get a huge boost in what you can see with a telescope like this.
That could allow, under the right conditions, the ability to directly detect exoplanets only a few
times larger than our moon, and even Mars sized rogue planets. Planets the size of earth should
easily be on the table for this telescope. The telescope also provides a coronagraph
for direct imaging of exoplanets, allowing us to get spectra of nearby giant planets.
And of course there will be ample room for individual researchers and of course serendipitous
events that come along, as with JWST. And the growth of our space telescope capabilities with
Roman and JWST will essentially provide some kind of replacement, but not exactly by any means,
for the aging Hubble Space Telescope, which we can essentially lose at any moment., Indeed last
year it almost failed, and many were saying it was the end for the telescope, but NASA has since got
it back up and running and doing science again. Estimates put its service life as lasting until
at least 2026, or longer with enough luck. But that may not be the end of the story for Hubble.
The thing about Hubble is that it was designed to be serviced, unlike James Webb.
The whole idea was to send up the Space Shuttle and crew to replace instruments
or change out obsolete ones, which happened a number of times, most recently in 2009.
But with the retirement of the space shuttle, it didn’t seem that we’d have the capability
to continue to service Hubble and keep it going. But this has changed with the very
rapid development of manned rockets in the US with spaceX, Blue origin, NASA’s SLS system and others.
It may now actually be possible to service Hubble again, especially with SpaceX’s crewed dragon
or eventually even robotically. This could give Hubble all new gyros and replace failed equipment
and essentially give new life to the telescope and keep it operating for a few more decades. Some
proposals have been made to this end, but nothing concrete, but at the rate human spaceflight is
developing it may very well happen and the venerable old telescope might see new life.
Thanks for listening! I am futurist and science fiction author John Michael Godier
currently worried about servicing the Hubble space telescope. What if we keep doing it for centuries?
I can see the headline now in the galactic daily newspaper, the Humans were inadvertently destroyed
after servicing the Hubble Space Telescope for the 242nd time. Not being the sharpest cookies
in the galactic jar, they installed generalized artificial intelligence and a space laser and the
telescope finally took its bitter revenge. Very disturbing and be sure to check out my books at
your favorite online book retailer and subscribe to my channels for regular, in-depth explorations
into the interesting, weird and unknown aspects of this amazing universe in which we live.