Department of
Electronic Engineering
La Trobe University
Victoria 3086 AUSTRALIA
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School of Engineering & Mathematical Sciences TIGER - Bruny Radar
In developing the Tasman International Geopspace Enviroment Radar (TIGER) the aim has been to extend the SuperDARN network in the Southern Hemisphere,
but with the important difference of extending coverage to the sub-auroral region. This provides opportunity to observe new phenomena and to improve the coverage of auroral phenomena during
magnetic storms when the aurora expands equatorward of the footprints of the other radars in the SuperDARN network.
The Bruny Radar footprint covers the lower latitude portion of the auroral oval and the ionospheric trough.
The Tasmanian component, located on Bruny Island, began operation in December 1999 but was officially opened on the 29th of May 2000. So here is a movie of the TIGER Bruny Radar commemorating the Opening Ceremony.
Due to the TIGER - Bruny radar's excellent geophysical location, gives unique opportunities to study Geospace processes such as the Aurora Australis
and related phenomena occurring in the ionosphere (100 to 300km) above the earth.
Since the radar is much closer to the south magnetic pole than the south geographic pole, this makes it an ideal location from which to monitor the interaction of the solar wind with the Earth's magnetic field.
Its more northerly location relative to the other Antarctic radars also allows it to better monitor events that move northwards during magnetic storms and out of the view of the Antarctic based radars.
The TIGER - Bruny radar is directly across the magentic pole from PACE, the British Antarctic Survey's SuperDARN radar at Halley, Antarctica. The TIGER - PACE will form a unique radar pair providing important simultaneous
measurements of the aurora in the noon and midnight sectors.
The TIGER - Bruny radar is based on the exisiting third generation HF radar constructed by the University of Leicester,
including improvements to the transmitters, power supplies and microcontrollers. This radar is a Mono system, transmitting one set of frequences at a time where as it's counterpart TIGER - Unwin is a Stereo Radar and transmits
two frequencies concurrently at one time. All SuperDARN radars use common basic operating software which can readily be adapted by each radar group for special operations or new modes which may later be adopted by the entire radar
network.
The basic specifications of the TIGER radar are listed in the table below;
Horizontal: 4° at 10MHz, 3° at 14MHz, 2° at 18MHz
Vertical: 50°
Lobe Levels:
<- 14dB for both back and side lobes
Transmitters:
16 x 600W (one per antenna in Tx/Rx array)
Total Peak Power:
9.6kW
Mean Power:
200W
Radiated Power:
12.5W in main beam direction
Tx Signals:
Pulse pattern duration: ~ 100ms
Pules width: 300us
Bandwidth: 10kHz at -20dB
Duty Cycle: 2.1% Carrier frequency
The radar operates as a fixed-frequency sounder, choosing a suitable frequency in the 8 - 20MHz band. The frequency selected is that providing the
greatest amount of ionospheric scatter across the radar footprint
and which, due to ionospheric motions, has a signficantly larger Doppler shift than sea or ground backscatter. The radars will switch to a different
frequency if there is more ionospheric scatter there and this can happen once every few hours.
Frequent changes in operating frequency would make it difficult to separate temporal variatons of ionospheric and magnetospheric phenomena from
progation changes caused in operating frequency.
The transmitting antenna consists of 16 log-periodic, 10 element, horizontally polarised antennas supported by 15m towers. Each antenna is fed by its own
600W power amplifier and a phasing network is used to scan the main beam of the array over 52° of azimuth in 16 steps. The antenna horizontal beamwidth
varies with frequency and pointing direction but is ~3°. A much broader vertical beamwidth (~50°) facilitates the detection of echos with
ranges as small as 180km and as great as 3330km. Both TIGER radars pulse enable the same antenna array to be used for transmission and reception.
An auxiliary receiving array of 4 antennas forms an interferometer to measure the elevation angle of arrival. In the most common modes of operation TIGER
completes a full azimuth scan in 1 or 2 minutes.
TIGER typically operates near 14MHz during day-time and 12MHz at night but this changes with the level of solar activity. It is also capable of swept-frequency
operation meaning that when irregularities are widespread throughout the ionosphere, the radar detects ionospheric and sea scatter over much of its range window
and over abroad band of frequencies as can be seen below.
Content Approved by: Principal Investigator: Prof. P.L. Dyson
Page maintained by: Webmaster
Last Updated: 7th March, 2005
