A rough, tough sensor

The weather data publicly accessible on the Web is only a portion of the meteorological data collected by the Australian Bureau of Meteorology. Not linked to the Web are the dozen automated weather stations (AWS) locatedhundreds of miles away from the bases.

The location of these stations means that they must be engineered to "operate unattended forever," according to Mark Underwood, the electronics design engineer who built the stations. The stations were designed to be deployed once and then checked ten years later.

The design specifications laid down for the stations are what could euphemistically be called "challenging." Each AWS must be self powered, transmit data via satellite, able to withstand strong winds and blizzards, and survive in temperatures that may go as low as -70C. Underwood says that most commercially available weather stations stop operating at -20C. The stations collect data on wind speed, air temperature, solar radiation, wind direction, barometric pressure, subsurface temperature and humidity. In addition, a "snow sonar" located at the top of the stations sendssignals down at the base to record the snow depth.

Bulldozers are occasionally sent out to locate the stations before they get lost. "We like to find them before they get completely buried." Solar panels keep lead-acid batteries charged, but because the batteries lose up to 80% of their charge at -60C, the power consumption of the stations must be matched appropriately. The highest power drain comes from the satellite transmitter.

Data from the stations is sent back via an asynchronous satellite link, called Argos, but the bandwidth is such that at times only 24 characters per hour can be transmitted. Without the satellite unit, the station could run for about 20 years on a large torch battery, according to Underwood. The data from the stations is made available to scientists and researchers via databases that are created at the Australian Antarctic Division. Underwood said that the researchers generally create their own databases, populating them with the sensor data that is relevant to their research.

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