Eye in space

Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.

James Webb has visual superpowers

LIFE OUT IN DEEP SPACE is not for the faint-hearted. Blasted by charged particles from the Sun, subjected to freezing temperatures, battered by micrometeoroids and even just getting up there entails being shaken almost to bits. Fortunately, a particularly sensitive piece of equipment that will give us insights into a period of the universe’s history not yet seen has emerged with a clean bill of health from testing that includes deep freezing and alternately being pounded with electromatic impulses and being vibromassaged by sound at deafening volumes.

NASA describes the James Webb Space Telescope, due to be launched in 2019, as the world’s premier infrared space observatory of the next decade. It will orbit the Sun, one and a half million kilometres away from the Earth at what is called ‘the second Lagrange point’, or L2. What is special about this orbit is that it lets the telescope stay in line with the Earth as it moves around the Sun.

A barrier-breaking mission for engineers and astronomers, Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international programme led by NASA and its partners, the European Space Agency (ESA), and the Canadian Space Agency (CSA). It’s the scientific complement to NASA’S Hubble Space Telescope.

Webb, though not able to see back to the beginning of the universe, will look further back than Hubble did. Webb was designed to see a period of the universe’s history not yet observed, specifically, the first objects that formed as the universe cooled down after the Big Bang, according to Dr John Mather, senior project scientist for Webb and a man who knows a thing or two about the subject (he won the Nobel prize for his work on a previous space telescope).

Most recently Webb emerged from cryogenic testing at NASA’S Johnson Space Centre in Houston, Texas, in preparation for a move to California. That testing is important because the entire observatory must survive the mechanically stressing conditions from the violent action of launch. In addition to this, the “cold” half of the observatory – the telescope and its instruments – must survive the thermal shrinkage that occurs when they are cooling from room temperature to the cryogenic temperatures at which they operate in the cold of space, says Paul Geithner, deputy project manager – technical for the Telescope at Goddard Space Flight Centre in Greenbelt, Maryland. The engineering challenge is to operate Webb at extremely cold temperatures, since Webb is built at room temperature. Webb has to survive years in space, exposed to the radiation from the Sun and the galaxy.

Vibration testing not only shows that the telescope can survive the rigours of launch, but also verifies the workmanship that went into its construction.

For lower frequencies of vibration, from about 5 hertz (cycles per second) to 100

hertz, it’s placed on a surface – basically a big metal plate – that rides on bearings so it can move back and forth. “This surface is connected to essentially a big electromagnet that generates the shaking motion,” Geithner says.

“For higher frequencies, above 100 hertz, it is very difficult or impossible to achieve the necessary vibration with a big vibration table system, so instead we put the hardware in an acoustics chamber. This is a thick-walled room with large speakers that produce literally deafening levels of sound.”

Super-cold or “cryogenic” tests are carried out in a big vacuum chamber using liquid nitrogen and helium gas to achieve temperatures that approach between 10 and 20 Kelvin (between minus 263 degrees Celsius and minus 253 degrees Celsius – the temperature of the cold helium gas).

Webb’s sunshield of deployable booms and gossamer polyimide membranes – it looks like a silver kite, the size of a tennis court – help keep the telescope and instruments cold because Webb is an infrared telescope. For an infrared telescope to be as sensitive as possible, its optics and scientific instruments need to be extremely cold, so their own heat does not blind them to the faint infrared signals they are trying to observe from astronomical objects.

Almost all of Webb’s sensitive components (besides the mirrors and sunshield) are protected behind “micrometeoroid armour”. When micrometeoroids do strike, most are so small that they totally disintegrate upon impact, even when they hit something thin like thermal blankets or a sunshield membrane. Critical wires and electronics are shielded behind even more robust metal “armour” or inside metal boxes. – NASA Goddard Space Flight Centre/eric Villard