The James Webb space telescope: in search of the secrets of the Milky Way

The most expensive robot probe ever built will be blasted into space in a few weeks. The launch of the observatory, which has been plagued by decades of delays and massive cost overruns, will be the most nervously watched liftoff in the history of space exploration.

The observatory was built by Nasa and European and Canadian space agency collaboration and was designed to find life-supporting planets in our universe. The project has taken more than 30 years to plan and build, with it suffering cancellation threats and political controversy. Several other scientific projects had to be canceled to meet the huge price tag of the observatory. Nature said this is the telescope that ate astronomy.

When the telescope is fired into space on December 22nd, scientists will discover if those costs are justified. The European Space Agency says it is the launch of a generation.

The flight mirrors of the telescope are being tested at the Marshall Space Flight Center. Alamy.

The James Webb is a much bigger, more complex instrument than the Hubble space telescope and has many more ambitious goals. The visible part of the spectrum will not be studied, but it will be able to see the part of the spectrum that is not visible.

The director of the UK Astronomy Technology Centre in Edinburgh says there are many reasons for this. The perfect part of the spectrum for looking through dust is IR, because stars and planets form in regions full of dust. If you want to understand where and how other solar systems are being created, the James Webb should provide crucial data.

The atmospheres of planets that may contain chemicals such as methane are best studied by gathering the radiation from the sun.

A telescope is used to time things. You can see what the universe was like in the past.

Prof. Martin Ward.

Wright is the European principal investigator for the team that built one of the four main instruments: the MIRI or Mid-infrared instrument. The other three devices will also study the spectrum.

This part of the James Webb's operations will involve looking at stars in our own universe. Astronomers want to study the very early universe in the period after the big bang, when the universe was only a few billion years old. That means looking at very, very distant objects. Key advantages are provided by studying IR radiation.

A telescope is a time machine. Prof Martin Ward of Durham University is a member of the MIRI science consortium and he says that it allows you to see what the universe was like in the past. Light gets fainter and redder the further back you look into the universe, until it reaches the part of the spectrum that's in theIR. If we want to study how the first stars, black holes and galaxies formed, we need anIR telescope.

The ground observatory can operate at the wavelength of the sun, but telescopes need to be above the warm, wet atmosphere to get the best views. Thousands of scientists and engineers have struggled to overcome the technical hurdles thrown up by the design of the telescope, which has led to countless delays.

The telescope won't be able to rely on human aid once it's launched. Hubble is in low Earth orbit, where astronauts on the space shuttle were able to repair and service it. The shuttle was grounded a decade ago and so the James Webb has been designed to operate without any help from humans.

Instead, it will be fired on a trajectory that will take it to a region known as the second lagrange point, where the gravity of our planet and the gravity of the sun cancel each other out. The telescope can be kept in the same position, where it can operate for 24 hours a day. Small gas engines will be burned to make sure the craft stays at L2.

It will be easier to keep the James Webb cold at Lagrange 2. The telescope was designed to operate at 40C above absolute zero so that it wouldn't generate spurious heat signals that could swamp the faintIR radiation it receives from the other end of the universe. The telescope will be protected by a five-layer shield that will block out radiation from the sun and Earth, and it will also be chilled by a liquid helium refrigerator.

The observatory will have to overcome a lot of risk. There is a danger of failure with the launcher. Since 1996, the Ariane 5 has had a total of 106 successful liftoffs. The failures occurred early in the rocket's development schedule and it is now rated as a highly reliable launcher. There is a chance that it will fail as it leaves Esa's space port in French Guiana. That is still a scary prospect, given the amount of money, time and effort already spent on the project.

Those who are not worried or scared about this are not understanding what we are trying to do.

Thomas Zurbuchen is from Nasa.

That is just the beginning. The telescope will be slowly unfurled as it cruises across space. The first sheets of foil will act like giant parasols to keep the telescope cool. The main mirror of the telescope will be next to appear. It is seven times larger than Hubble's mirror. It is a fact that putting large objects in space is a lot harder than launching small ones. That has been a challenge for the telescope.

To get round the size issue, the designers of James Webb built a mirror that is made of 18 hexagons of gold-coated beryllium mirror. The mirror will be created by slotting together and unfurling like a flower.

This automated self-assembly will take around six months to complete and will have to work perfectly. Astronomers will only find out if the James Webb is going to be a great technological triumph or a dollar-destructive disaster after that. Thomas Zurbuchen, Nasa's associate administrator for science missions, says that those who are not worried or terrified about this are not understanding what they are doing.

The Ariane 5 rocket is being prepared. NASA.

A different perspective on the caution and delay that has affected the telescope is provided by the project manager of the MIRI instrument 10 years ago. She says that she was going into secondary school when the idea of the telescope was agreed. I am a mother and a successful project manager and the telescope has not been launched.

More than 200 engineers and scientists have worked on MIRI alone to make sure the observatory operates perfectly once it is in the correct position. The components were provided by a European consortium and assembled at the Rutherford Appleton Laboratory.

It was put in test chambers, which had all the air sucked out of them, and temperatures were reduced to levels that the telescope will experience in space. After it passed the cyrovac tests, MIRI was integrated with the telescope's other three detectors and sent to Nasa. It takes a long time to do this sort of thing, but it will be worth it.

The delay has had other consequences. Politics has moved on since 2002 when it was originally named. Many scientists think the name is inappropriate since they accuse James Webb, a former Nasa administrator, of removing gay and lesbian people from jobs in the 1950s and 1960s. The controversy is likely to linger despite the space agency's refusal of such demands.

The telescope's mirrors were packed in canisters before being shipped to Nasa. NASA.

It's not clear what the James Webb will discover. Hubble has been in operation for three decades and has helped determine the age of the universe, determine the rate at which the universe is expanding, and show that nearly every major galaxy is anchored by a black hole.

Astronomers will be expecting more this time. Their hopes are that by studying how stars are born and evolve, they will be able to understand the potential for life to appear in planetary systems. The lifetime of the James Webb will have to be done in a decade. It is expected that the telescope will no longer be located at L2 after 10 years because it will run out of fuel. It will become the most expensive piece of space junk ever built.

It is not likely that the observatory will be as expensive or complex as the James Webb will be. These are like Christmas trees. They have many different instruments attached to them. Smaller and cheaper telescopes will be preferred by space agencies in the future. This could be the last Christmas for space astronomy.