TIGER opens second eye across Tasman

Thursday, 11 August, 2005



TIGER - the Tasman International Geospace Environment Radar - is taking a much larger bite at southern skies following the opening in February of its second radar base in Invercargill, New Zealand.

It is now helping to measure the impact of auroras and detect echoes from meteors.

Operated by a consortium of Australian Research Institutes headed by La Trobe University, TIGER is part of the international SuperDARN (super dual auroral radar network) operated by 10 nations to cover both southern and northern polar regions.

The New Zealand 'Unwin radar' link follows TIGER's first radar built on Bruny Island in Tasmania in 1999.

The new radar is named after New Zealand scientist, Dr Bob Unwin, a pioneer of ionospheric studies in the 1950s and 60s who set up an auroral radar in New Zealand and explored the possibility of having a second radar in Tasmania.

It was opened by his son, Martin Unwin, a scientist with the National Institute of Water and Atmospheric Research Ltd, Christchurch, New Zealand.

La Trobe University Head of Physics, Prof Peter Dyson, principal investigator of the TIGER project, delivered a public lecture on 'The Unwin Radar - A New Look at the Aurora and Other Impacts of the Solar Wind', before the opening.

La Trobe was represented at the opening ceremony by Assoc Prof in Electronic Engineering, Dr John Devlin, the scientist-engineer responsible for the development of the radar system and colleague Dr Harvey Ye; deputy vice-chancellor (research) Prof Brian Stoddart; and dean of the faculty of science, technology and engineering, Prof David Finlay.

TIGER monitors the location of aurora and related phenomena in the ionosphere, 100 to 300 km above the earth.

Results from its full operation will include greater knowledge of space physics and space weather processes to help manage radio communications, navigation systems such as GPS, satellite operations, magnetic surveying for minerals and occasionally, under extreme solar conditions, impacts on electricity supplies.

La Trobe operates TIGER on behalf of a consortium that also comprises Monash University, University of Newcastle, the Australian Antarctic Division, IPS Radio & Space Services and the Defence Science and Technology Organisation.

TIGER's first component, which uses a 300 m long antenna on Bruny Island, probes a 52° sector in azimuth with a range from 200 km south of Tasmania to the Antarctic coast 3000 km away.

The New Zealand component is an improved 'stereo' version of the Bruny Island radar.

The radar's electronics were built on La Trobe University's main Melbourne campus in Bundoora and installed with another large antenna array near Invercargill on Awarua Station, a farming property that is the site of one of the first radio communications stations in New Zealand.

Prof Dyson says each radar emits beams that cross, giving different line-of-sight velocities that, combined, provide scientists with accurate 'vector' velocities of motions in the highly disturbed auroral ionosphere.

TIGER explores an area half the size of Australia by directing HF radio signals via the ionosphere towards Antarctica and detecting weak echoes from structures in the ionosphere.

These echoes are used to form images of the ionospheric structures and measure their speed and direction of motion. It also detects echoes from meteors which are used to calculate wind speeds at heights of around 100 km and it can detect signals from the sea.

Prof Dyson says when the sun's corona ejects huge amounts of matter that reaches the earth, there are rapid changes in wind speed and temperature in the ionosphere as well as the magnetosphere, the outer region of the earth's magnetic field.

Auroras are caused by electrons striking molecules and atoms after entering the atmosphere near the poles.

Auroras can move 500 km in less than a minute during magnetic storms and can disrupt communication and navigation systems.

TIGER monitors such storms and can provide real-time data on space weather storms.

TIGER uses HF radio waves in the 8-20 MHz range.

Although it transmits pulses with a peak power of 9.6 kW, it consumes only 2 kW of power, the same as some electric kettles, and transmits an average power of 200 W - the same as two bright light globes.

Reprinted from the La Trobe University Bulletin.

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