The technology behind the James Webb Space Telescope

By Mariusz Bogacki, Researcher and Science Communicator, Edinburgh

We are all amazed by the recent images produced by the largest space telescope in history. But how does the Webb actually work?

James Webb Space Telescope (JWST), or simply the Webb, is the largest space telescope in history. It is 100 times as powerful as its predecessor, NASA’s Hubble Space Telescope, and its objectives include searching for extra-terrestrial life and understanding the origins of the universe. Many scientists believe its discoveries will usher a new age of astronomy. No pressure there!

The technology behind such sophisticated technological marvel is a result of more than 20 years of planning and development and it is almost as mindboggling as the first images it has produced. Originally projected to cost $1 billion, the final price ended up being $10 billion, with 12 years of delay from its originally planned mission in 2010. It is finally here though – well, actually up there! – and scientists hope its discoveries will make up for the delays.

The Webb is the biggest ever telescope built by NASA. Because of its large size JWST had to be folded up and transported by a space rocket to its location nearly one million miles away from the Earth. It took about two weeks for the unfolding procedure to take place. Once unfolded, the science operations, and space exploration, could begin.

The telescope is operated by Integrated Science Instrument Module (ISIM) that provides electrical power, computing resources, cooling capability and structural stability. ISIM also holds four science instruments and a camera that do the bulk of data collection, analysis and data transfer back to Earth.

JWST is a reflecting telescope. This means it collects data by reflecting different types of light through its two gold-coated mirrors. The more light its golden mirrors can reflect, the more things it can see in the universe. The Webb’s primary mirror intercepts red and infrared light that travels through space and reflects it onto a smaller secondary mirror. The secondary mirror then directs the light into the recording instruments.

The telescope is capable of capturing and collecting different types of light such as ultraviolet or gamma rays. It can therefore capture things that the human eye is not capable of. What’s more, the Webb is able to analyse the atmospheres of faraway galaxies. This means scientists will be able to detect chemicals such as water, CO2 or methane, bringing us closer to answering the age-old question – is there life beyond our blue planet?

Importantly, the reason for the far away location of the telescope is not only for the purpose of reaching out to the furthest galaxies but also to avoid capturing the light generated by the Earth or the Sun. Because the telescope observes very faint infrared signals it needs to be protected from any bright, light sources such as the Sun. The mirror of the telescope is therefore shielded with a tennis court size protective shield, that prevents the light coming from the Earth and the Sun.

Unlike the Hubble Telescope, the Webb is unserviceable and unfixable. It is simply located too far away from Earth. The impressive technology behind its construction will really come to a test once we know it will not break. Hang in there Webb-y!