Dr debunks satellite myth

Surveillance capabilities and uses of satellite imaging are being misrepresented in today's media, according to an Australian expert talking at a security conference in Sydney on Tuesday.

Dr Dave Johnson, from Australasian ImageNet, a Canberra business dedicated to satellite image distribution services, told attendees at the University of Technology, Sydney conference that satellites' surveillance powers were not as far-reaching as some might believe.

"With satellite technology, you cannot read car number plates, recognise people or read newspapers. And we'll never be able to do these things," said Johnson.

Measured in resolution, satellite technology could get down to 10 or 20cms, Johnson said. However, US Congress has imposed limits on radar and optical satellites, restricting the resolution of the latter, and most powerful type, to 65cm.

Information on the capabilities of military satellite technology, however, is not available.

"Nearly all satellites are subject to shutter control," said Johnson. "This restricts parts of the world from being seen to satisfy military requirements."

As they are programmed from ground stations, satellites can receive updated controls over where they may monitor on each orbit.

Geostationary satellites must be of low resolution, such as those used for weather forecasting. Satellites that orbit the earth are also subject to restrictions.

"Satellites that orbit the earth are subject to a revisit period, which governs how often they can see the same spot on the earth," said Johnson.

High resolution imagery can also be embargoed by governments for 24 hours prior to its release.

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