The James Webb Space Telescope (JWST) is set to launch on October 31st of this year, marking the start an exciting new era in telescope technology and space exploration. The result of decades of work, JWST is the planned successor to the iconic but ageing Hubble telescope currently in orbit. After being plagued by delays and budget overruns for many years, NASA is finally ready to launch the most advanced telescope ever sent into space.

Decades in the making
The way we see the universe literally changed forever when NASA launched the Hubble telescope back in 1990. This powerful telescope was on the leading edge of astronomical technology at the time, and has continued to give us an unrivalled view of the cosmos ever since.

Designed to be repaired and upgraded by astronauts in orbit, Hubble has received 5 separate servicing missions over the years, the last being in 2009. However, since the retirement of the Space Shuttle in 2011, Hubble is no longer able to receive any further upgrades. The telescope is still operational, but it is beginning to show its age. Hubble celebrated its 30th birthday in 2020 and while it may operate well into the 2030’s, the optics are quickly falling behind our current modern technology. NASA had already begun planning a new telescope to replace Hubble as early as 1996. While Hubble observes in mostly visible and near-infrared light, JWST will observe the universe in the full infrared spectrum, giving astronomers incredible views of some of the most distant objects ever seen in the universe.

Another one of NASA’s space observatories named Spitzer was an infrared telescope that had been operating since 2003, but it was shut down after the mission ended in 2020. This left a huge gap in infrared astronomy, and the need for the JWST is greater than ever.

The initial plan was a 2007 launch with a budget of between $500 million – $1 billion USD, but this quickly became an unrealistic goal after years of redesigns, spiralling budgets, and technical challenges.

Hubble is an icon in astronomy, but the telescope is beginning to show its age (NASA)

Plagued with delays
The JWST today stands at a total development cost of roughly 10 billion USD, much higher than the early estimate of up to 1 billion. Many of the delays were due to the main contractor who was hired to make much of the telescope, Northrop Grumman. Numerous human errors in testing causes a succession of delays, like using the wrong solvent on a fuel valve, or applying the wrong voltage to the telescope during a test. The company itself was pressed by the U.S Congress who approves funds for NASA, with some stating the company should pay for the mistakes and delays caused by their errors.

Northrop Grumman is an easy scapegoat for some, but the delays go much further than just the build contractors. Much of the cost and long development time is down to the fact that large amounts of the required technology did not even exist when the telescope was first proposed.

It would have been incredibly complex for NASA to forecast the true cost of the project, as many of the parts needed had never been made before. The telescope was not simply an upgraded version of Hubble, it was a completely new type of telescope that required largescale innovation and technological advancements. Actual construction did not begin until 2008, and by then the development cost had ballooned to $5 billion USD. The earliest launch date with that time frame was 2015, but the telescope’s issues kept popping up and the delays and costs grew accordingly. NASA announced in 2018 that the telescope was scheduled to launch in 2020, and the cost by then had again shot up to $8.8 billion USD. The 2020 launch date was again pushed out due to the COVID-19 pandemic. But now, the telescope is virtually completed and launch preparations are all set for October 31st, 2021.

Engineers clean a test mirror with carbon dioxide snow (NASA/Goddard)

Another serious factor in the delay of the telescope is the fact that JWST cannot be upgraded or repaired. Unlike Hubble which orbits the Earth some 500km above, JWST will be sent deep into space to an area known as L2 about 1.5 million km from Earth. This is far beyond the reach of a repair mission by any current spacecraft.

When NASA first launched Hubble, it quickly became apparent that they had made a mistake in the construction of the telescopes mirror. Images were blurry and unfocused. It was an embarrassing mistake for NASA, but fortunately the telescope was designed to be fixed and upgraded. Astronauts visited Hubble in 1993 with corrective optics that fixed the problem, and the repair was declared a success. No such fix will become available to JWST should anything go wrong. Scientists have had to extensively test every feature on the telescope dozens of times to ensure that JWST can work for a planned 10 years for its primary mission. Any single small issue could render the entire project, and billions of dollars worthless, should anything not work properly.

                                                                    A folded up JWST undergoes a series of tests (NASA/JPL/NASA Goddard)

A powerful successor
Despite the numerous delays, now that the telescope is almost ready for launch it is worth celebrating just how momentous an achievement in science and technology the JWST represents.

The sheer size of the telescope was a challenge from the beginning. Whereas Hubble has a primary mirror of 2.4m and it could be launched into space as a single piece, JWST’s primary mirror has a diameter of 6.5m. Astronomers have had to work around the size limits of what rockets could carry, and have devised an ingenious solution to create an origami-like telescope that could be folded for launch and unfurled once in space. The main mirror consists of 18 smaller hexagonal mirrors that can be folded up during launch. This also allows the mirror to fine-adjust the position of each mirror, giving the telescope a much higher resolution and focus of the stars.

JWST’s main mirror consists of 18 smaller beryllium-plated mirrors that create a honeycomb (NASA/JPL)

Another essential feature that allows JWST to observe very faint infrared light is the tennis court-sized sunshield. To see such faint and distant objects in infrared, the telescope must also be cooled to -223°C. The five-layer sunshield, each layer as thin as a human hair, was constructed from Kapton E, a polyimide coated with aluminium on both sides and silicon on the Sun-facing side of the two hottest layers. This reflects the Sun’s heat back into space, and accidental tears of the delicate film structure during testing in 2018 were one of the many setbacks in development.

A view of JWST once the sunshield and primary mirror has been opened (NASA)

One of the primary goals of JWST is to not only study the stars, but to also study planets that orbit other stars. Thousands of exoplanets have been discovered in recent years, but so much about these foreign worlds remains unknown. Telescopes like Kepler could detect basic information like the size, mass, and orbit around a star, but it could not tell us more crucial information like what the atmosphere is made of.

JWST is expected to be able to study and directly detect what chemicals make up the atmosphere of some exoplanets, giving us a greater understanding of how exoplanets form and if any of they would be able to sustain life. JWST will also be capable of studying the objects in our own solar system, including planets, comets and asteroids.

Hubble’s mirror compared to JWST (NASA)

When JWST launches, it will have a resolving power of over 100 times that of Hubble. Just like when Hubble first launched and changed our understanding of the universe, the James Webb Space Telescope is soon set to embark on an incredible voyage of discovery. It will unveil many currently unknown secrets of the cosmos and further our understanding of the universe and our place within it.