Not so bright Tiger

A high-profile technology development project, launched in June by the UK science minister, has ended in failure and disagreement about its goals. The Star Tiger programme, funded with 500,000 Euros (£320,000) by the European Space Agency, was initially supposed to develop a terahertz wave sensor capable of producing a colour image of an object.

Terahertz waves operate above 100GHz and are emitted naturally by all materials. They allow objects to be seen through cloud, smoke, paper, clothing and even walls. The different frequencies of wave make up a colour image, which enables the user to determine which materials an object might be made of. Imaging is possible without the dangerous radiation of X-rays.

Star Tiger was an experiment in improving technology development by assembling a specialised team of 11 researchers and removing their administrative responsibilities, in a bid to compress two years’ worth of work into four months. But the project leader, Dr. Chris Mann, admitted this week that the prime target of producing a colour image of a hand was not achieved.

‘We didn’t have enough time to image a hand in colour. It was only one of the objectives, but we ran out of time. We really should have had a follow-up period after testing to clear everything up.’

However, Niels Jensen, head of ESA’s technology research department, claimed the project was a success. He said the agency had wanted better methods for monitoring the earth and distant suns using terahertz sensors. ‘All the goals were achieved. For a project of this type it worked very well.’

He said new schemes would be selected for the same development approach, and an announcement on the project’s outcomes would be made in the next few weeks after patents had been finalised.

The work was carried out at the Rutherford Appleton Laboratory in Oxfordshire, with the aim of building a working prototype by September. Six months on, the final report is still being written. Although it missed its original target it did image a hand in black and white within three months.

Mann’s team set out to place many terahertz detectors on a silicon wafer. Each detector would be either a photonic band gap wafer or photo polymer on a silicon base.

The photonic band gap is a micro-machined honeycomb structure with gaps small enough to direct a single terahertz wave. The photo polymer is a submicron-sized spike with a length directly proportional to the wavelength it can absorb. The waves captured by these devices would then be processed to make up an image.

Because of the early successes Mann said they had generated potential spin-offs and once the patents were completed they would reveal more details.

In the US a more complicated active system, which fires terahertz energy at its subject, has been developed for airport security. It presents images in 3D and different materials emerge as different colours.

If made to work, passive terahertz sensors such as those attempted by Star Tiger could be used to detect skin cancers or provide images of the area around an aircraft and possible enemies without giving away its position.