The Davis MFSA radar

Ice-covered area has an array of radar masts.
The radar hut and some of the masts that support the MFSA radar antennas. (Photo: Damian Murphy)
Industrial computers and screens on a bench

The Australian Antarctic Division, in conjunction with the Adelaide University Physics Department and Atmospheric Radar Systems Pty. Ltd, operates a 1.94 MHz MFSA (Medium Frequency Spaced Antenna) radar at Davis station in Antarctica.

The main role of the MFSA radar is to measure the wind speed and direction through the height range 50–100 km. These heights correspond to the mesosphere (approximately 50–85 km) and the lower part of the thermosphere (above 85 km). They also correspond to an altitude range where regions of turbulence create a disturbance in the atmosphere that is strong enough to weakly reflect the radio waves that are transmitted by the radar. The movement of these turbulent patches can be measured by looking at their radar reflections. Given that they move with the wind at the reflection height, the wind speed at that height can be measured.

To measure the movement of these patches, the radar reflection is measured at three antennas spaced out in a triangle (the Spaced Antennas in the name MFSA). By measuring the movement of the reflected radio waves over these antennas it is possible to calculate the wind speed.

The radar consists of a radio transmitter that sends radio pulses upward through a group of four antennas arranged in a square. Three receive antennas pick up the reflected waves and these are amplified through radio receivers. A computer is used to control the radar electronics and another computer is used to convert the received signals into measurements of the wind.

The MFSA radar is part of the Australian Antarctic Division’s focus on the global climate system. This takes the form of observations of the dynamics and thermodynamics of the polar atmosphere. Measurements of the wind at heights above those sampled by standard meteorological instruments help us to learn about processes that affect the climate and weather of the southern hemisphere from above. Atmospheric wind speeds measured by the radar, in combination with measurements of the mesospheric temperature, using a scanning spectrometer, and measurements of density and temperature with an atmospheric LIDAR, allow the collection of a unique and useful data set.

The Davis MFSA radar is supported by Antarctic Science Advisory Committee funding. The project name is, “Dynamic Coupling in the Antarctic Middle Atmosphere” and the chief investigator is Prof. Bob Vincent of the University of Adelaide.

The radar is maintained by the Climate Processes and Change program’s wintering engineer at Davis. Upgrades and troubleshooting activities are carried out by the above investigators in conjunction with staff from Atmospheric Radar Systems.

In one image in the above gallery, the eight masts of the square transmitting array are visible against the blue sky. On the far left, one of the receiver antennas is visible. It has been painted so that it can be seen from the helicopters that sometimes fly over this area. On the horizon (middle right) there is another receiver antenna. The white building in the foreground houses the radar electronics. The second image shows the inside of the radar control hut containing the radar transmitter, receiver and controlling PCs. The PC in the left-hand rack samples the data and controls the operation of the radar. This rack also houses the radio receivers and sampling equipment. A second PC sitting between the racks takes these data samples and converts them into wind speeds. Another electronics rack houses the solid state transmitter.