Aeroplane spotting using a radio telescope

An international team of scientists, led by Olaf Scholten, Professor of Astrophysics at the University of Groningen, has observed radio wave-emissions originating from a commercial airliner, most likely caused by the discharge of static electricity. The serendipitous observation of radio wave emissions from specific locations on the aircraft may be of interest to the aviation industry. In addition, this has already enabled the team to identify a source of error in their imaging techniques. The results were published on 26 November in the journal Nature Communications.

Static electricity builds up through friction, for example, between your clothes and the fabric of your chair, but also in aeroplanes when they pass through frozen clouds. Aeroplanes are therefore fitted with electrostatic discharge wicks, which are designed to shed electrostatic charges in a way that does not cause dangerous sparks or interfere with the aircraft’s communications. Interestingly, the discharges observed by Scholten and his team, while the aeroplane was cruising at an altitude of 8 kilometres, were located around the two engines and at one spot on the tail, rather than at the electrostatic discharge wicks. The events near the tail were measured with an accuracy of about 50 cm.

Of interest to the aviation industry

The observation was made using the Low-Frequency Array (LOFAR) radio telescope, an antenna network located mainly in the Netherlands and spanning seven other European countries. This telescope is primarily used for astronomy, but also for studying the formation of lightning. In previous work, Scholten and his colleagues used LOFAR to make the most detailed lightning images in the world. Thanks to the serendipitous discovery of the aircraft’s emissions, the researchers were able to improve their technique, which will make lightning detections even more accurate in the future.

Flight data revealed that the observed aircraft was a Boeing 777-306 (ER) from the Dutch airline KLM. After searching their archives, Scholten and his colleagues found emissions from a second aircraft, flying at an altitude of 11.6 km. These emissions were also located around the engines and at one point on the tail.  These observations demonstrate that it is possible to use LOFAR to study the accumulation and discharge of electricity by aircraft flying through clouds. Scholten: ‘This would be of interest to the aviation industry, as static charges can create sparks that may damage the plane.’

Reference: Olaf Scholten et al., Measuring location and properties of very high frequency sources emitted from an aircraft flying through high clouds. Nature Communications, 26 November.