Click on Images for larger view.
All results presented on this web page are from December 3rd 1998. These results are very preliminary, they contain nothing but the most basic filtering techniques for the removal of airplane, ground and sea clutter. The radar will operate until the end of December with raw data stored to disk. The aim is to obtain a large data set so that algorithms can be developed to remove aircraft clutter in a wide range of airport conditions.
Results were obtained over a period of 2-3 hours in which the radar operated with a temporary power connection. Gaps in the data are due to testing of different radar parameters and different modes of operation.
The observations presented provide only an initial indication of the capabilities of the system. Many factors, ranging from changes in aircraft activity, atmospheric conditions and analysis procedures prevent these data from being regarded as "typical." The page will be updated as more data become available and as the analysis techniques are refined.
Two different modes (Low and High) were used.
The low mode enables us to measure down to 400m (300m occasionally) using a 150m pulse length. The data were oversampled with a resolution of 100m. The transmitter being used in this prototype system has only 1KW of peak power so a longer pulse was used to obtain measurements to higher altitudes. In the high mode a 4.5 m s (600m) pulse was used to increase the effective power, although this has the drawback of smoothing the measurements. Again the high mode was oversampled with 150m resolution.
The received power provides a measure of the gradients in radio refractive index. In the lower troposphere the major contributions are due to humidity, temperature and turbulence. The two images below are of the power profiles for the two modes plotted as a function of time.
LEFT: This is for the high mode from 0435-0535 UTC (1535-1635 AEDT). An increase in the profile can be seen just below 3 km. This is due to a temperature inversion as confirmed by a radiosonde launch around the period. The missing sections of data are due to removal of strong echoes from aircraft.
RIGHT: This is for the low mode from 1230-0530 UTC. Note, the long gaps in the data are due to the radar not transmitting in this mode at all times in this interval. Strong returns from the inversion below 3 km are very well defined. As for the high mode observations strong echoes from aircraft were removed. After 0400 UTC aircraft activity increased, as can be seen at heights above 3 km where short duration regions of enhanced echo strength can be seen.
Shown below are examples winds measured over the periods given above for the two different modes. The first image is from the high mode. Aircraft interference can be seen where the velocities are significantly larger in magnitude than adjacent values and often point in different directions (i.e. 0502 UTC at 4.3 km).
The next three images obtained using the low mode focus on the lowest observed heights. The first image shows the total period of observation. The second zooms in on a period of low aircraft interference. During this period aircraft were taking off from the EW runway and landing to the north on the Main and Third runways. This diagram shows the potential of the system for low altitude coverage. The time resolution is about one minute; no averaging is used. The final image shows a period of increased aircraft activity when aircraft were taking off to the south on the main runway and passing close to the main beam of the radar. A reduction in successful measurements is noticed as well as spurious and incorrect measurements of the wind velocity. Algorithms to remove the aircraft echoes from the raw data are now being developed.
