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Use of a data recorder for quality monitoring of weather radars

Where planes and the weather is concerned, functioning radar technology plays a fundamental role. The technical performance of radar antennas is highly relevant in this regard. That is why armasuisse Science and Technology is working together with MeteoSchweiz on a device that checks the quality of weather radars and antennas.

15.04.2020 | armasuisse Science and Technology, Sensor

Lema Radar
Monte Lema Radar

Weather radars, like the Monte Lema radar in Tessin shown, scan the sky systematically for precipitation. Here, the radar assumes the functions both of a transmitter and of a receiver. In a joint project, armasuisse Science and Technology (S+T) and MeteoSchweiz are developing a pulse logger, a data recorder which monitors the signals transmitted by a weather radar and thus ensures the quality.

If the weather radar is in transmitter mode, radar pulses are generated and emitted in a particular direction. The physical parameters of these pulses vary depending on the radar’s area of application. These include, for example, the frequency and amplitude of the electromagnetic carrier waves, the pulse duration and the repetition rate in terms of time of the pulses.

If transmitted radar pulses are reflected, for example off a raindrop, their physical parameters change. Now in reception mode, the weather radar collects these reflected radar pulses and analyses the change in the pulse form in addition to the duration. The radar can thus not only determine the distance to the precipitation area, but also the precipitation type, such as drizzle, heavy rain, etc., as well as the direction and speed of the propagation.

In order for the reliability of these evaluations to be ensured, the weather radar is dependent upon pulse data that is as accurate as possible. Flawless technical performance of the weather radar antenna in transmitter mode is essential for this purpose. As external factors can also influence the antenna characteristics at the operating location, an examination of the mode of operation of radar antennas under laboratory conditions is insufficient and too complex.

S+T and MeteoSchweiz therefore want to set up a remotely operated data recorder, also known as a pulse logger, directly at a radar operating location. The pulse logger, which outwardly resembles an external hard drive, is to monitor the weather radar during operation on site and analyse the quality of the transmitted radar pulses. This pulse logger is known as a Software Defined Radio (SDR). This means that a part of the signal processing is realised using software. This SDR pulse logger records the transmitted weather radar pulses via its own antenna system and not via the weather radar’s system. This additionally increases quality assurance. The software required for this purpose has been developed by the research department Sensory Analysis (WTS) as open source in the programming language Python 3. The pulse logger software analyses the pulses transmitted by the weather radar and reflected off a raindrop and then presents the resulting pulse parameters and antenna characteristics in a user-friendly manner.

Thanks to this pulse logger, the weather control stations of the weather radars can access this visually prepared data at any time and at any place and provide an overview of system-relevant radar antenna parameters. The proper functioning of the weather radar antennas in transmission mode can thus be checked quite simply by remote access and the data can be used to analyse the weather conditions – all without a time-consuming journey to a weather radar.

The pulse logger is currently at the laboratory in Thun and is being tested by WTS for long-term stability.

puls-logger
Pulse logger: Data recorder for quality monitoring of weather radars