Largest ever
‘We are getting very nervous now’, says Cardiff University’s Dr Peter Hargrave. It’s no wonder; Hargrave has spent around 12 years working on the SPIRE project (Spectral and Photometric Imaging Receiver) for the Herschel mission, the largest astronomical telescope ever put into space.  It is due to be launched this month from the European Space Agency site in French Guiana. Herschel is named for British Astronomer, William Herschel, who discovered infrared radiation in 1800 while studying the sun.

Hargrave leads the Cardiff team and the whole SPIRE project required the specialist knowledge of scientists, including those from institutions in France, Canada, China, Italy, Spain, Sweden and the USA. The project’s Principal Investigator is Professor Matt Griffin, also from Cardiff’s School of Physics and Astronomy.

Looking into the past
Cardiff has one of the largest astronomy instrument building groups in the world, and leads the design and scientific input for the SPIRE instrument. ‘We specialize in doing astronomy at a very long wavelength, looking at very distant galaxies, seeing how galaxies are forming. By looking at galaxies 10 Billion light years away, you’re essentially looking 10 billion years into the past as the light from that galaxy has taken 10 billion years to reach us.’ Hargrave says that they are hoping to get answers to the big questions in astronomy, such as how the sun and the galaxy are formed. ‘We can observe the very earliest stage of star formation,’ he explains. They hope to see the clumps and dust of stars before they have been ‘turned on.’

Cooling down
‘Anything that has any temperature at all’, says Hargrave, ‘emits light of a certain wavelength. The colder it is, the longer the wavelength. Ice cubes emit light, we look at stuff that is much colder.’ And the reason they are putting this telescope into space is that the earth’s atmosphere absorbs these long wavelengths.

They have to cool the cameras down on the telescope, otherwise only the radiation from the cameras would be visible. ‘The whole satellite is cooled by 3000 litres of liquid helium’, says Hargrave. ‘That cools everything to about 2 or 3 Kelvin, minus 371 degrees centigrade. The detectors on board the SPIRE instrument are then further cooled down to about 300 millikelvin, that’s about 0.3 of a degree above absolute zero, and we do that in space.’ The scale of this feat of engineering may soon be matched by answers to some big questions.