James Webb telescope © NASA/Getty

When will the James Webb Space Telescope launch? All you need to know about Hubble’s successor

The biggest space observatory ever constructed will look further through space (and time) than any other telescope.

Dust off your countdown timers: after 15 years of development and $10 billion (£7.25 billion) spent, the James Webb Space Telescope (JWST) is ebbing ever closer to launch.


The successor to the Hubble Space Telescope, NASA’s new outer-Earth observatory is not only expected to deepen our understanding of the Milky Way, but also far-away exoplanets and celestial objects. Able to capture a wide range of light wavelengths, the JWST also hopes to observe the Universe’s first galaxies and find even evidence of dark matter.

But when exactly will the JWST first launch? How does the observatory compare to Hubble? And what is its official mission? You can observe all the answers below.

When will the James Webb Space Telescope launch?

An Ariane 5 rocket during launch in 2017 © Getty
An Ariane 5 rocket during launch in 2017 © Getty

An Ariane 5 rocket carrying the James Webb Space Telescope is expected to launch on 31 October 2021 (Halloween) at French Guiana. An exact time of launch is yet to be announced.

The observatory was originally scheduled to blast-off in 2007, but has since faced 16 launch delays.

In early 2020, NASA projected the JSWT would be ready by March 2021. However, after the coronavirus pandemic and social distancing restrictions forced delays in testing, lift-off was postponed once more.

Who is James Webb?

James Webb in 1966 © Getty
James Webb in 1966 © Getty

The James Webb Space Telescope is named after James Edwin Webb, the second administrator of NASA.

Webb was best known for heading Apollo, the space programme that first sent humans to the Moon. However, he was also instrumental in overseeing the two crewed space programmes that preceded Apollo: Mercury and Gemini.

To make way for a successor chosen by a new incoming president (Richard Nixon), Webb left NASA in late 1968. This was several months before Neil Armstrong took one giant leap for mankind on the lunar surface (20 July, 1969).

Webb eventually died in 1992, aged 85.

“It is fitting that Hubble’s successor be named in honour of James Webb. Thanks to his efforts, we got our first glimpses at the dramatic landscape of outer space,” said former NASA administrator Sean O’Keefe about the observatory’s name. “He took our nation on its first voyages of exploration, turning our imagination into reality.”

Before being named after James Webb in 2002, the JWST took the title of the Next Generation Space Telescope. Which yes, is very Star Trek.

How big is the James Webb Space Telescope?

NASA employees stand by a full-scale replica of the James Webb Telescope © NASA
NASA employees stand by a full-scale replica of the James Webb Telescope © NASA

Billed as the successor to the Hubble Space Telescope, the JWST is the largest space observatory ever built. Its gigantic sunshield base measures a massive 22m by 12m, roughly the same size as a tennis court.

Although nearly twice as big as Hubble (which is only 13m long), the JWST is almost half the weight at 6,500kg.

The JWST’s gold-plated mirrors have a total diameter of 6.5m, much larger than Hubble’s 2.4m diameter plate. Overall, the JWST will have approximately a 15 times wider view than Hubble.

How far can the James Webb Space Telescope see?

Using its infra-red telescope, the JWST observatory will examine objects over 13.6 billion light-years away.

Because of the time it takes light to travel across the Universe, this means that the JWST will effectively be looking at objects 13.6 billion years ago, an estimated 100 to 250 million years after the Big Bang. This is the furthest back in time ever observed by humanity.

Where will the James Webb Space Telescope orbit?

After launching into space, the JWST will orbit the Sun, flying up to 1.5 million kilometres from Earth in temperatures reaching -223°C.

For comparison, the Moon is 384,400km away, while the Hubble Space Telescope flies only 570km above our planet. As the JWST will operate so far away from Earth, it will not be able to be serviced by astronauts if any faults arise.

What is the James Webb Space Telescope’s mission?

As the JWST is a product of an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA), it has many mission goals.

These include:

  • Examine the first light in the Universe and the celestial objects which formed shortly after the Big Bang.
  • Investigate how galaxies form and evolve.
  • Study the atmospheres of distant exoplanets.
  • Capture images of planets in our own solar system.
  • Locate evidence of dark matter.

The JWST is expected to operate for five years after its launch. However, NASA hopes the observatory will last longer than 10 years.


Unfortunately, the observatory won’t be able to operate forever: although mostly solar-powered, the JWST needs a small amount of finite fuel to maintain its orbit and instruments.