An unprecedentedly designed, ultra-sensitive and far-reaching backward-looking cosmic observatory that will extend and complement Hubble's discoveries

The $10 billion for an electronic super-eye named James Webb

photo_camera PHOTO/Northrop Grumman - A hundred times more powerful than Hubble, JWST is capable of detecting the light of a single firefly from a million kilometres away

At last, the most sophisticated, largest, most expensive and most disruptive space telescope of all time is about to take flight in an attempt to discover the life cycle of stars, from birth to death.

On Christmas Day, 25 December, at 01:20 a.m. CET, a European Ariane 5 launcher will take off from French Guiana with the hopes of thousands of astrophysicists from all over the world placed in its precious payload. If it succeeds, years and years of delays, a serious attempt by the US Congress to cancel the project and an incessant trickle of billions, amounting to the astronomical figure of nearly 10 billion dollars, around 8.5 billion euros, will be left behind.

This costly 6.2 tonne technological colossus has been given the name James Webb, in memory of the man who between 1961 and 1968 was the all-powerful head of the National Aeronautics and Space Administration (NASA), the driving force behind the Apollo moon programme under the auspices of President John F. Kennedy and also the advocate of the Agency's central focus on scientific research.

James Webb fue el administrador de la NASA entre 1961 y 1968, impulsor del programa lunar Apolo y defensor a ultranza de que la investigación científica fuese el eje de la Agencia

The James Webb Space Telescope (JWST) is a huge, powerful and ultra-sensitive observatory that will expand and complement the discoveries of the legendary Hubble, which has been in operation for more than 30 years, to which it is heir, but with which it bears no external or technological resemblance. 

A hundred times more powerful than its predecessor Hubble, the JWST operates in the near- and mid-infrared wavelengths, and is "capable of detecting the light of a single firefly from a million kilometres away," says NASA. But its purpose is not to find tiny insects in the Universe, but to "look back more than 13.5 billion years, penetrate cosmic dust clouds and observe objects far away," says Catarina Alves de Oliveira, a scientist at the European Space Agency (ESA). 

La NASA y el fabricante Northrop Grumman han llevado a cabo centenares de ensayos de desplegado del espejo primario y de la sombrilla. En esta última intervienen 8 diminutos motores y centenares de mecanismos
Hubble 570 kilometres from Earth, JWST 1.5 million kilometres away

An initiative led by NASA with the cooperation of the Canadian Space Agency (CSA) and ESA, with contributions from science, industry and Spanish institutions - such as the National Institute of Aerospace Science (INTA) and the Centre for Astrobiology (CAB) - the James Webb aims to find the first stars and galaxies that were born after the Big Bang.

It has also been designed to study the "embryonic elements that gave rise to the formation of planetary systems and the evolution of black holes, as well as to analyse the atmospheres of exoplanets that may harbour carbon, nitrogen, oxygen, iron or some kind of life", emphasises Macarena García Marin, responsible for the calibration of the Euro-American instrument MIRI, one of the four on board the telescope.

But could the research to be carried out by the JWST be done with telescopes installed on the ground? Not really. The Earth's atmosphere is not transparent to many of the infrared bands, which are also degraded by chemical compounds such as carbon dioxide, methane and water vapour. And can't the veteran Hubble do it? Well, neither can it. Its optics are adapted to the visible and ultraviolet spectra, it has been in operation for more than 30 years and is nearing retirement.

La NASA y el fabricante Northrop Grumman han llevado a cabo centenares de ensayos de desplegado del espejo primario y de la sombrilla. En esta última intervienen 8 diminutos motores y centenares de mecanismos

The positioning of the two telescopes relative to the Earth is another difference. Hubble is in orbit 570 kilometres from the Earth's surface. This short distance has allowed NASA's space shuttles to reach it to repair its faulty original optics and upgrade its equipment and software, which is impossible to do with JWST. 

What is the reason for this impossibility of repair in case of serious anomalies? The JWST will be positioned and remain for a minimum of 5 years at a distance of 1.5 million kilometres from the Earth. This is the so-called L2 Lagrange point, a stable location in the Earth-Sun system from which it will orbit the sun. To get an idea of the magnitude of the distance at which the new telescope will be placed, suffice it to say that the Moon is about 400 000 kilometres away from us.

Las principales contribuciones de la ESA al James Webb son un instrumento científico, compartir el desarrollo de otro con la NASA y aportar el lanzador Ariane 5 que lo debe poner en órbita
Akin to putting a boat in a bottle

The revolutionary new telescope consists of a main mirror 6.5 metres in diameter, equivalent to a total surface area of 25 m2, seven times larger than that of Hubble. It consists of 18 lightweight hexagonal plates made of beryllium and coated with 48.25 grams of gold - about the size of a golf ball - which reflect the faint infrared light very well. Behind them are four infrared spectrometers and cameras: one developed by NASA (NIRCam), one by Canada (NIRISS), one by ESA (NIRSpec), and one equally owned by NASA and ESA (MIRI).

The on-board equipment is completed by communications antennas, in-orbit stabilisation systems and high-precision guidance and orientation sensors. All this is protected by a huge 300 m2 sunshade - the size of a tennis court - with five layers of special aluminium and silicone coatings. This ensures that the large mirror and the four instruments are kept at a constant temperature of -233 degrees Celsius - close to absolute zero - and prevents the 85 degrees Celsius of radiation from the Sun reaching the bottom of the umbrella from degrading the measurements. 

Una de las 18 placas hexagonales fabricadas en berilio y revestidas con 48,25 gramos de oro, lo que equivale al tamaño de una pelota de golf

In total, the maximum dimensions of the JWST are 21.2 x 14.2 x 8 metres. In contrast, the dimensions of the upper part of Ariane 5 are 5.4 metres in diameter x 17 metres in height. This requires the large telescope to be folded into the rocket, a bit like "putting a ship in a bottle," says NASA's current head, Bill Nelson.

Once the telescope is launched and released into space, 27 minutes after liftoff the solar panels will be activated and hours later the sunshade will begin to open very slowly. Eight tiny motors and hundreds of mechanisms, cables, hinges and pulleys will be involved," says Krystal Puga, a systems engineer at Northrop Grumman, the mission's prime contractor, which will continue for the first three weeks of its journey to L2.

El Hubble lleva 31 años de servicio en órbita. Colocado en el espacio a 570 kilómetros de la Tierra, la NASA ha efectuado cinco vuelos tripulados para sustituir equipos deteriorados y actualizar sus capacidades

It is then up to the large mirror to expand and adjust with great precision. According to Mike Menzel, the mission's lead systems engineer, "275 failures can occur in the process of opening the sunshield and mirror," but these actions have been repeated hundreds of times on the ground and technicians are confident that there will be no surprises. Now fully configured, JWST is due to reach its final destination three months later. But all that remains is to calibrate and test the four instruments. NASA knows the risks, does not want any surprises and will proceed step by step, so scientific observations will not begin until 6 months after liftoff.

The James Webb telescope has far exceeded the cost of the Hubble telescope, which was in the order of 1 billion dollars. In contrast, the JWST has been a bottomless pit into which NASA has poured huge sums of money. The main reason for the cost overruns was largely due to a lack of awareness of the enormous technological challenge the Agency faced. From an initial $500 million budgeted in 1997, the overall figure has grown to around $10 billion, with NASA contributing $8.8 billion, ESA about $600 million and the rest from the Canadian Space Agency. 

Slightly smaller than a bus, Hubble was transported into space on 25 April 1990 by the shuttle Discovery. Its robotic arm extracted it from the cargo hold and deposited it in orbit. However, serious flaws in its optics and desirable improvements to its systems forced NASA to make five flights between 1993 and 2009 to obtain the first quality images, replace damaged equipment and upgrade its capabilities, all of which were carried out by American astronauts. With JWST, this is no longer feasible.

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