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Nasa is preparing to test its next-generation space telescope in a giant thermal vacuum chamber, with stunning photos revealing engineers hard at work ahead of testing of the James Webb Space Telescope (JWST).

The historic chamber was once used to test manned spacecraft, but has now been refurbished for this larger and more sensitive piece of equipment.

Various components of the telescope are now being tested ahead of the planned launch in 2018, when it will be used to study distant stars, galaxies and even exoplanets. 

Nasa is preparing to cryogenically test its new telescope in a vacuum chamber (shown) in Houston, Texas. The huge Chamber A at the Johnson Space Center is being refurbished to accommodate the telescope

The huge vacuum chamber in which part of the telescope is to be tested is called Chamber A and is located at Nasa's Johnson Space Center in Houston, Texas.

'This is what space science is all about,' said Nasa photographer Chris Gunn, who captured a photo from outside the enormous mouth of the chamber.

'There is nothing else like this that anyone will see in their day-to-day lives.'

Engineers and technicians, dressed in sterile suits and secured by harnesses to stands for safety, are seen inside Chamber A preparing a lift system that will be used to hold the telescope during testing.

Once fully assembled and launched into space, the telescope will allow scientists to explore ever further into the cosmos, seeing things that even the mighty Hubble Space Telescope can't.

Before the telescope is launched one million miles (1.6 million km) into space to its destination, it must undergo a series of detailed tests to ensure it's ready for the harsh environment of space.

This spring, a model of the telescope called Pathfinder will begin cryogenic optical testing inside this chamber.

'Maintaining the schedule with a very large number of optical and ground support equipment integration efforts, while securing the telescope to a suspension system inside the chamber and conducting a cryo-strength test is an incredible integration and test challenge,' said Mark Voyton, manager for the Optical Telescope Element and Integrated Science Instrument Module (Otis). 

This coming spring a test model called Pathfinder will undergo cryogenic optical testing inside the chamber (engineers seen at the mouth bottom left). A suspension system (right) inside the chamber will hold the telescope in place as it is cryogenically tested

The JWST is the scientific successor to Nasa's Hubble Space Telescope.

It will be the most powerful space telescope ever built, and is an international project led by Nasa with its partners, Esa and the Canadian Space Agency.

Earllier in December the JWST's Integrated Science Instrument Module (ISIM) structure endured a 'gravity sag test' as it was rotated upside-down in what looked like a giant cube in a Nasa clean room at the Goddard Space Flight Center in Greenbelt, Maryland. 

The purpose of 'cubing' the ISIM was to test it for gravity sag, which is to see how much the structure changes under its own weight due to gravity.

The James Webb Space Telescope's Integrated Science Instrument Module (ISIM) structure recently endured a 'gravity sag test' as it was rotated in what looked like giant cube in a Nasa clean room (pictured)

Inside Nasa's Goddard Space Flight Center's giant clean room in Greenbelt, Maryland, JWST Optical Engineer Larkin Carey examines two test mirror segments recently placed on a black composite structure. This black composite structure is called the James Webb Space Telescope's 'Pathfinder' and acts as a spine supporting the telescope's primary mirror segments. The Pathfinder is a non-flight prototype

The ISIM is one of three major elements that comprise the Webb Observatory flight system. The others are the Optical Telescope Element (OTE) and the Spacecraft Element (Spacecraft Bus and Sunshield).

Engineers need to see how gravity affects the alignment of the instruments within the module when the ISIM is in different orientations on the ground.

They use measurements from this sag test to verify what the instrument alignments will really be in space, when there is no preferred direction from gravity, and take account of sag during assembly with the telescope.

The cube with the ISIM inside it was rotated using a massive machine called an Aronson table; the rotation was just the dramatic start to the test. The cube and ISIM were then lifted off of the rotation table while inverted and kept upside down for several days while lasers made precise position measurements. 

The Secondary Mirror of the JWST Pathfinder (test) Telescope is shown here being stowed in the large cleanroom at Goddard Space Flight Center. Instrumentation will be added to the telescope arms to monitor temperatures during cryogenic testing in the Chamber A thermal vacuum facility at Johnson Space Center in 2015