Mission impossible

The European Space Agency has recruited a crack team to develop a terahertz imager. The goal: to achieve in four months what normally takes two years. Will it succeed?

When it comes to technology, time waits for no man. Technological advances are so rapid today that the job delayed is not worth doing. And the way industry keeps pace is to throw people and resources at a problem over a concentrated period for quick solutions.

The technique hasn’t been attempted in public sector R&D programmes, however – until now. Over the next four months a multidisciplinary team assigned to a European Space Agency project will attempt to develop a revolutionary terahertz imager capable of generating a picture of any object from the energy it gives off, from concept to prototype in just 16 weeks.

If successful the project will produce a camera designed to be mass produced cheaply. The imaging array will represent a breakthrough for observing Earth from space and could have dramatic implications for the next generation of astronomy systems. It will also have applications in fields as diverse as aeronautics and medicine. But, equally important, it will serve as a model for future projects in strategically important areas of research.

The project, known as Star Tiger, was given a high-profile launch by science minister Lord Sainsbury. It has 11 engineers and scientists, drawn from research institutions throughout Europe, and will be based at the UK’s Rutherford Appleton Laboratory in Oxfordshire, where all the necessary equipment and administrative support is. Other distractions will be removed allowing full concentration on the problem. No paperwork is planned for the team, while administrative processes such as buying basic resources and materials to fabricate the sensor, which usually takes weeks, will be done in a day.

The decision to move to four months in an attempt to emulate industry is no accident, according to industrial innovation expert Prof Luke Georghiou of the University of Manchester, who has just completed a global study of R&D in industry.

He says: ‘Projects that once would have been on a 10-year timescale are now being carried out over two years. Industry’s view is that with the market moving so quickly if the work cannot keep pace then it is not worth doing. From the sound of it the Star tiger project has a clear objective and with people working in one place they will probably achieve their goal.’

ESA has a department dedicated to transferring technology to the private sector, but its projects normally last two years or more. To compress this Star Tiger will receive all the funding, e500,000 (£320,000), it would get over two years.

The team will build on previous research into gigahertz frequency sensors involving ESA and RAL. In 2001 UK, Dutch and Spanish researchers working for ESA were able, for the first time, to combine a micro-machined terahertz antenna with a silicon photonic band gap wafer. This is a tiny mesh whose holes are so small they can control the capture of terahertz waves accurately enough to enable imaging.

In addition, workers at the Rutherford Appleton Laboratory succeeded in building the world’s first micro-machined subharmonic mixer at a frequency of 0.5THz. Its role is to reduce the frequency of the 300GHz energy wave arriving at the array to a manageable 5GHz to produce an image. It is known as subharmonic because its signal will be half the frequency of the incoming wave.

Chris Mann, a radio frequency engineer, is team leader for Star Tiger. He and ESA project manager Peter de Maagt proposed the idea to ESA’s head of technology programmes, Niels Jensen. Mann says: ‘The two earlier developments together provided the real possibility of laying out an array of terahertz detectors into a charge-coupled device imager type. The way in which the array will be configured has not yet been decided as this will be the first challenge for the team.’

What they do know is that the array will fit on to a silicon wafer and could consist of either the photonic band gap wafer, or a photo polymer on a silicon base, or perhaps a hybrid of both. This last option is currently being simulated.

The photo polymer is a layer of polymer whose surface is ‘spiked’ with structures whose height is directly proportional to the frequency of the signal they must intercept.

The Star Tiger team’s imager will detect two frequencies, 250GHz and 300GHz. This will allow the researchers to contrast substances within objects with different transmission and reflection properties, while for remote sensing from orbit the detection of more than one frequency would allow simultaneous measurement of two atmospheric constituents.

Once the signal has been received by the array it will be combined with a signal from an oscillator and the combined signal amplified to create an image. The initial radiated energy signal can be as low as 1012W at room temperature, the energy output of a human hand. The project’s defined initial goal is to be able to create the image of a hand at a distance of 1m.

Because of all the potential commercial applications intellectual property rights are a hot issue among participating institutions, all parties hoping to be involved had to sign an agreement that they would retain ownership of existing IPR that they brought to the project, but any new intellectual property from Star Tiger would be owned jointly by the participating parties and used by them for research purposes.

Any commercial exploitation has to have an agreement on ‘proportional distribution’ of the proceeds, based on each party’s relative input. If successful RAL hopes to receive future rapid projects for ESA.

The high-profile approach ESA has adopted to Star Tiger is also high risk. But Niels Jensen is not perturbed by the prospect of failure. He feels ESA can still learn from the experience. His view is that the attempt to realise this technology rapidly will take this area of research a few steps further.

Jensen explains that he was prepared to try this once to see whether it would succeed: ‘Of the e250m (£160m) research budget we have e2.5m (£1.6m) to give towards innovation. I would have liked to have had two projects both receiving e500,000 (£320,000), one being four months long and the other two years to compare. But unfortunately I do not have that much money.’