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The term Terahertz generally refers to the frequencies too high for microwave technologies, and too low for optical technologies. This is taken to be from around 30Ghz up to just below infra-red. The StarTiger program is definitely a THz technology.

There are more interesting THz imaging projects. An academic named Zhang has done very interesting work at bio-imaging at THz frequencies.

Personally, I'm not convinced of the breadth of applications of THz imaging that this article suggests. Terahertz frequencies are strongly absorbed by water, meaning that it is virtually impossible to look deep into such things as the atmosphere or body.

Imaging is possible down to a few millimetres within the body, and is therefore perfect for detecting skin cancers, and some other kinds: but it is entirely impossible that it might replace Xrays for more than a couple of applications. Analysing fractures or breakages would never be possible, for example.

The atmospheric limitations are quite drastic, though this can be a good thing for short range telecomms (your wireless comms attenuating severely after a few tens of metres, and not reaching the next office block, for example). There is a very interesting THz astronomy project based in the Antarctic: the low humidity means that THz are not attenuated a great deal, and very interesting images can be derived from this.

The interesting thing is that it is practically the only set of frequencies that we have, until now, been unable to look at in space. It might not be as revolutionary as radio or xray astronomy, but many are hopeful that it might demonstrate very useful results.

Andrew