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2\11 ESA - Space camera blazes new terahertz trails
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European Space Agency

Press Release

Space camera blazes new terahertz trails
========================================
11 February 2003

New imaging technology came to life when ESA's StarTiger team captured 
the world's first terahertz picture of a human hand. 

"When we started last June we set an ambitious goal: to build in four
months the first compact submillimetre-wave imager with near real time 
image capturing using state-of-the-art micro-machining technology," 
said Peter de Maagt, ESA's StarTiger Project Manager, "we reached this 
goal when the first terahertz images were taken in September."

This breakthrough in terahertz imaging opens up the possibility for a
new generation of applications, not only related to space but also in
many non-space fields, including medicine, pharmaceuticals, security
and aeronautics.

StarTiger is a new approach for conducting research and development
(R&D) launched last year by ESA. The concept is to bring together a
small group of highly motivated researchers, grant them full access to 
laboratory and production facilities, remove all administrative
distractions, and let them work for an intense period of four to six
months. The goal is to achieve a quantum increase in a promising and
important technology within a short period of time.

The first project was started at CCLRC Rutherford Appleton Laboratory 
(RAL) in June 2002 and was scheduled for four months. RAL was chosen 
as the best location for this particular pilot project with its 
advanced laboratories and all support technology required, and its 
specific expertise in relevant fields.


What is Terahertz? 
------------------
Terahertz waves occupy a portion of the spectrum between infrared and
microwaves, from 10¹¹ to 10¹³ Hertz.

Until now, this has been an unexplored part of the electromagnetic
spectrum. However, terahertz waves are very interesting as they
possess characteristics of both their neighbours: terahertz waves can
pass easily through some solid materials, like walls and clothes, yet
can be focused as light to create images of objects.

The imager built by the StarTiger team takes pictures at two
frequencies, 0.25 and 0.3 THz, to create a two-colour picture to
create a contrast between materials with different transmission and
reflection properties.

The main advantage of a terahertz imager is that it does not emit any
radiation; it is a passive camera capturing pictures of the natural
terahertz rays emitted by almost everything, including people, rocks,
water, trees and stars. 


Space Applications
------------------
The imager could be applied in several areas of space science,
including astronomy, atmospheric physics, and Earth and environmental
monitoring by satellites. In the field of planetary, cometary and
atmospheric sensing, it could have a major impact on instrumentation
for monitoring issues.

In space astronomy, observing terahertz frequencies could provide
answers to some key questions on how galaxies were formed in the early 
universe, and how stars form, and have been forming, throughout the 
history of the universe.

For environmental monitoring, a terahertz imager could be used to
obtain data for studies on ozone depletion mechanisms. The frequencies 
can be selected to focus on exchanges between the troposphere and the 
stratosphere, adding information useful for studies on global climate 
changes.

"Observations from space may be on the verge of a revolution with the
possibility of looking into the terahertz frequency range," said de
Maagt. He emphasized that the wide array of potential applications for 
such an imager must not be underestimated.

"Apart from its use on space missions, our everyday lives could soon
be reaping the benefits of this innovative technology," he added. 


Non-space applications
----------------------
If possible space applications are numerous, many more have been
identified in non-space fields for use on Earth. A terahertz imager
could open up a whole new range of systems in a variety of fields on
Earth.

For instance, the imager could have various uses in the medical,
dermatology and cosmetic sectors. Terahertz imaging is rapidly
becoming recognised as a totally new diagnostic technique. By
observing these types of waves, it is possible to see through many
optically opaque materials. Terahertz waves could provide an image
that has X-ray-like properties without the use of potentially harmful
radiation. A terahertz imager is a passive instrument and, since the
source of the signals for such an imager occurs naturally, is
completely safe. 

X-rays are important tools for dentists to evaluate patients' teeth
and to pinpoint cavities and other signs of disease that might not be
detected through only a visual examination. The terahertz imager could 
complement X-ray examinations without adding further health risks. No 
single type of sensor can provide all the information required for 
most tasks and combining the use of different sensors could become a 
valuable tool in many other medical fields. 

Terahertz waves are also able to penetrate the uppermost layers of
skin, making the early detection of skin cancers an interesting
possibility. Skin cancer is usually curable if detected quickly
enough. Looking into terahertz waves could provide earlier detection
than is possible today.

And what about looking behind a dressing to see if a wound is healing
correctly? This again should be possible using terahertz instrument.

An application of a different nature could be the detection of
chemical and biological threats. As all materials emit terahertz
waves, each having it own frequency pattern as a kind of
'fingerprint'. It could be possible to identify not only the existence 
of powder in envelopes and postal parcels, but also which kind of 
material is enclosed.

In airports, it could be possible to see through clothes and identify
weapons, but not based upon the metal-detection techniques used today. 
Even non-metal explosives could be possible to spot since they may 
have their own terahertz 'fingerprint'. 

"By exploiting operations at two frequencies 250 and 300 GHz, it
should be possible to discriminate between materials of different
types based on their optical properties e.g. reflectivity," said Roger 
Appleby, Technical Leader for the Passive Millimetre Wave Imaging 
Group at QinetiQ, a UK company. "When imaging the body, reflectivity 
falls and emissivity increases as the frequency is increased. These 
properties could be used to reduce false alarms in images of people 
collected for security scanning."

(continued)

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