Australasian Science: Australia's authority on science since 1938

Circuits for Satellites

By Stephen Luntz

For a wide brown land, the prospect of finding water has always been tantalising. Now a final-year engineering student has found a way to contribute to this quest, winning a scholarship to attend the NASA Academy in the process.

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The proposed Garada project will bounce L-band radar signals off the land below to study 300 km-wide strips of soil for water content. The system relies on rapid switching between broadcast and receiving mode. However, the challenge that was set to Cooney was to slow down the frequency with which pulses would need to be sent out.

“If you reduce pulse repetition frequency you can improve the images that are returned, and the demand on other parts of the system is less high,” Cooney says. “You can spend less money on equipment and get the same quality images.”

Such a challenge could have been daunting for an undergraduate student, but Cooney set about combining all the system requirements in a more efficient manner and designed the circuit on his computer. “The most rewarding thing about the project was getting the finished board back from the assembler, and holding in my hands a design I had been staring at on a computer screen for months,” Cooney says.

“If you send a polarised signal through the atmosphere, a range of factors change it,” Cooney explains. “Normally one mitigates by using all polarisations – sending on horizontal and receiving on vertical for example. You need lots of frequency to do this. However, if you can just send a signal once and run a sequence of captures you don’t need to send so many times. You can cut down by around four the...

The full text of this article can be purchased from Informit.