What Comes After James Webb Space Telescope?
The James Webb Space Telescope was unprecedented. What comes next?
In 2021, astronomers and space enthusiasts across the globe received the finest Christmas present they could imagine.
On 25th December 2021, the James Webb Space Telescope (JWST) was launched from ESA’s spaceport in French Guiana; a culmination of three decades of hard work, heartbreaks and perseverance. Despite 334 single points of failure identified before launch, the 6,200 kg space telescope was placed into orbit without a hitch.
The current estimated lifespan for the James Webb telescope is roughly two decades, a fraction of the time spent by over 20,000 engineers, scientists and astronomers to bring the project to fruition. The conceptualization started at the Space Telescope Science Institute (STSI) in 1989 when director Riccardo Giacconi urged staff members to “think about the next major mission beyond Hubble.”
Even before the Hubble Space Telescope was deployed in 1990, a mission idea had started taking shape.
Since then, the team has faced several technological challenges, errors in development and issues with funding which led to an unprecedented delay in its launch. To add some context, the design phase for Hubble started in 1978 and it was launched in 1990 —a span of mere twelve years.
However, the JWST is unlike any other telescope ever made; NASA, the European Space Agency, and the Canadian Space Agency were practically trying to reinvent the wheel.
Consider this….
- The James Webb Space Telescope has been designed to detect infrared light (along with optical and ultraviolet wavelengths). This allows astronomers to observe stars, exoplanets and galaxies that are farther away and older than those visible in optical light, such as those detected by Hubble.
- The James Webb Space Telescope is the largest space telescope ever constructed with a primary mirror measuring 6.5 meters in diameter. As it collects more light than any other telescope in history, astronomers can view deeper into space than ever before.
- The James Webb Space Telescope is equipped with a five-layer sunshield that protects it from the Sun’s heat and light. This sunshield, the largest ever flown in space, measures 21 meters x 14 meters — roughly the size of a tennis court!
- The James Webb Space Telescope orbits the second Lagrange point (L2), 1.5 million kilometres from Earth; an ideal location for observing the universe outside the Earth’s atmosphere and away from the Sun’s heat.
Given this (partial) list of JWST’s incredible accomplishments, you may begin to understand why the telescope took so long to be deployed.
Yet, as was the case with Hubble, astronomers are already “thinking about the next major mission beyond JWST.”
But how can you improve on something that is undoubtedly the zenith of technological innovation and space engineering?
How do you outperform a reinvented wheel?
The answer lies in reinventing the most critical component of any telescope.
Not to sound like your high-school physics teacher, but a space telescope’s mirror focuses the light traveling through space and analyzes it using onboard instruments. Even the slightest miscalculation in the mirror’s curvature can lead to, well, disaster!
When the Hubble Space Telescope was launched in 1990, scientists quickly realized that the primary mirror’s curvature was flawed. The dimension was off by 2.2 microns — smaller than a red blood cell!
To fix the problem, NASA engineers devised a plan to install corrective optics during the second servicing mission in 1993. Spacewalking astronauts made the changes to the telescope’s optics, making it the first and only time that a major component of the Hubble Space Telescope was replaced. This entire operation cost a whopping $700 million — but it was worth it!
Before and after:
Even if the expense is justified, scientists wouldn’t be able to replace or adjust the curvature of JWST’s primary or secondary mirror given that the telescope would be 1.5 million kilometres away from Earth!
Hence, JWST’s mirrors were designed to allow astronomers to change their curvature using a simple actuator mechanism. Each of its iconic hexagonal mirrors is controlled independently using a combination of 7 actuators, which could curve each mirror to achieve the best optical performance.
Here’s the design of the mirror:
This insane engineering performed as expected, allowing the array of 18 hexagonal mirrors to achieve the required focus. This is what gave us some of the most stunning space images ever seen by the human eye!
So, the JWST gave us proof of concept. A folding mirror array, each with its independent actuators, can achieve the dynamic focus for new-age space exploration.
The question is: how can we improve on it?
Well, one of the first challenges James Webb Telescope’s scientists and engineers faced was the realization that the primary mirror would need to be 6.5 meters across to detect light emitted by very distant and faint objects. Building the massive mirror would be a herculean task — launching it into space even more so.
Yet, given how well the JWST has performed, scientists want to continue using the same concept — with one slight change.
One of the simplest things we can do is build a bigger mirror.
It may sound reductive — the bigger the better?
Yet, NASA has an ambitious telescope in their pipeline called the Large Ultraviolet Optical Infrared Surveyor, or LUVOIR. This multi-wavelength space telescope will observe space in ultraviolet, visible, and near-infrared wavelengths, and offer more versatility than JWST in terms of the scientific instruments it can carry.
The focus of the project remains unchanged from its predecessor: focus on identifying habitable exoplanets, imaging the re-ionization epoch, studying the formation and evolution of galaxies, etc.
What will change is its dimension.
The two proposed designs —LUVOIR-A, with a 15-meter diameter mirror and LUVOIR-B, with an 8-meter diameter mirror, dwarf the Hubble and JWST telescopes in comparison.
Building on JWST’s pioneering segmented mirror approach, the LUVOIR telescopes will detect bio-signatures in the atmospheres of distant exoplanets, including molecular oxygen, ozone, water and methane. LUVOIR-A is expected to study 54 potentially habitable exoplanets, while LUVOIR-B is expected to study 28 exoplanets. Despite the success of James Webb, these new-age telescopes will be key in understanding our Solar System in the context of the universe.
Fun Fact: The original acronym used for LUVOIR-B was “ATLAST”, a pun referring to the time taken to decide on a successor for Hubble Space Telescope.
The LUVOIR space telescopes will offer imaging up to 24 times sharper than the Hubble Space Telescope and an imaging resolution of 25 kilometres in visible light.
The quantum leap will be that the LUVOIR telescopes will have serviceable mirrors — that is, onboard robots will be able to repair or resolve issues with the mirror’s operation. While the JWST improved upon the shortcomings of Hubble, it sustained irreparable damage from micrometeoroid strikes in May 2022, and astronomers had to make adjustments for the distorted image. With this learning, the successor(s) of the JWST will improve upon its shortcomings.
At its core, the LUVOIR space telescopes will aim to answer a question as old as humanity itself: are we alone?
LUVOIR will give us a new window into the birth of stars, planet formation and the search for life. JWST remains the pinnacle of space exploration; it is the most powerful space telescope built — but not for long.
The James Webb Space Telescope is a truly remarkable project that is helping humanity explore the universe in ways never seen before. Yet, it is just the first stepping stone.
As constant advances in space technology are made, JWST will become “the Hubble” to future telescopes. We will develop an even better understanding of our place in the universe with future space exploration projects, such as the ambitious LUVOIR telescopes.
It is critical to remember the adage:
Space exploration is not an adventure, but rather a responsibility to push the boundaries of the unknown.
