James Webb space telescope: a glimpse into the depths of time

01/24/2022

As for space history, this year is off to a good start. NASA's new space-based observatory successfully moved the last three mirror segments of the James Webb space telescope into position on the 8th of January 2022. After a series of flawless engineering steps since the telescope's launch over Christmas, the most sophisticated, best-of-breed, next-generation space telescope ever built has now begun its operations. But the road beforehand had proved much bumpier than previously estimated.

 

James Webb space telescope: the beginnings

Launched in 1990, the Hubble telescope delivered unprecedented images and expanded our knowledge of the Universe around us. Now in operation for more than three decades, it has given us more accurate estimates of the age of the Universe, black holes at the centre of nearby galaxies and, of course, has made the news for its discovery of Earth-like bodies orbiting sun-like stars that may harbour life.

Time and technological advances over more than 30 years have made it necessary to replace Hubble. NASA itself does not like the term 'replacement' but prefers to use the more appropriate term 'scientific successor'. This is understandable. On one hand, the two advanced machines observe the universe in different ranges (James Webb's instruments will work primarily in the infrared range of the electromagnetic spectrum), and on the other hand Hubble is still the most important astronomical instrument in the world. Yet several factors have justified the succession from Hubble to the James Webb telescope.

 

Why is the James Webb space telescope replacing the Hubble space telescope?

The 1990 launch of Hubble was already beset by cost overruns and delays. And after the telescope was launched into space, it became clear that the revolutionary space equipment could not deliver the results scientists had hoped for. Unfortunately, the reason was very simple: its 2.4-metre mirror was the wrong shape. Consequently, expensive repair operations started, which could only be carried out in space. The distorted primary mirror was compensated for by adding smaller secondary mirrors. Even so, NASA was already keen to create and use a more advanced space telescope than its predecessor that would eliminate Hubble's primal faults.

In contrast to Hubble, one of the requirements for the design of the James Webb space telescope was that its successor should not orbit the Earth, since it was considered more useful for observation purposes to send it to one of the more distant Lagrangian points (L2) of the Earth-Sun system. The James Webb space telescope will therefore operate around the Sun, four times further away from the Moon's orbit, at a distance of about one and a half million kilometres. Its location and design are expected to lead to further major discoveries in astronomy, with a planned lifetime of about 10 years.

 

 

The scientific instruments

As one of the space mission's goals is to detect the light of stars and galaxies as close as possible to the time of the Big Bang, the space telescope must be able to see further than any instrument ever before. To achieve this, the telescope will have a much more sensitive detection system than before, capable of studying long infrared waves. But there was another problem that had to be solved. James Webb's detectors would go blind if the telescope emitted too much radiation at this wavelength because of its heat. To avoid this, the telescope is kept away from the Sun. It is also equipped with a five-layer shield the size of a tennis court, coated with DuPont Kapton aluminium and silicon (a polyimide film invented in the 1960s that remains stable between -269 and +400 degrees Celsius). The resulting shielding cools the telescope's mirror to between minus 233 and minus 223 degrees Celsius, significantly colder than the Hubble Space Telescope, which operates at room temperature.

 

James Webb space telescope – challenges of the mission

The initial sums, like those for Hubble, kept creeping upwards. Half a billion dollars was the first estimate, which by the turn of the millennium had climbed to over a billion. NASA expected the entire lifetime of the James Webb space telescope to cost close to $10 billion - although, as usual, co-production with the Canadian and European Space Agencies helped a lot, adding hundreds of millions of dollars to the US government's budget.

Continuous delays have not helped the project, and in 2018, during a vibration test, some of the bolts on the shielding unit came loose. This shook the confidence of decision-makers towards the main contractor, Northop Grumman, and led to an embarrassing inquiry hearing. Interestingly, it was the former US President George W. Bush who justified the government's decision to allow the new space telescope to go ahead despite the rising costs, to demonstrate the technological capabilities that had been a major factor since Sputnik. Congress, therefore, increased the programme's budget by an additional $800 million in February 2019, exceeding all the financial limits set up until then.

On 25 December 2021, to everyone's relief, the European Ariane 5 launcher carrying the James Webb space telescope was finally launched from the French Guiana Space Centre.

 

Unpacking a 9 billion equipment

The Hubble Space Telescope orbits in a near-Earth orbit, allowing astronauts to repair it. For the James Webb space telescope, this is out of the question because of the distance. So the scientific community and the public have been watching with bated breath to see if the unusual space instrument unpacking 1.5 million kilometres away. This was necessary because the light-gathering area of the 6.5-metre diameter unit is so large that no rocket in use today could carry it. Therefore the engineers assembled the mirror from 18 smaller hexagonal pieces, which were opened from a distance.

At the end of the complicated journey, all 18 mirror segments of the James Webb space telescope must have been adjusted, after which the cooling process could begin. The critical unique 175 failure points have now been successfully passed by the engineers and the five and a half month commissioning period should start soon. The first images from the new spacecraft are expected to arrive in the summer of 2022.

 

What can we expect?

The scientific instrumentation (module) of the structure houses a primary imaging device that scans the infrared range from 0.6 to 5 microns. This and other mechanics are expected to detect light from the first stars and galaxies in the universe. It will give mankind a glimpse into the cosmos's past. The expected lifetime of the telescope is five years, but NASA plans to make it more like 10 years.

After three decades of development, humanity's artificial "eye" will see further than at any time in history. It's worth following more news about the world's newest space telescope!

 

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