Lightning protection strategy used in LOFAR radio telescope

One of the anticipated threats for world's largest radio telescope with the acronym LOFAR is lightning. The synthesis telescope exists of at least 36 stations in The Netherlands and 8 European stations with a total antenna area of 0.29 km². The risk area is about 0.6 km² resulting in at least 1 hit every year assuming a typical lightning density of 2 km^-2 y^-1. Cost-effective protection measures have been taken at printed circuit board (PCB) level of antennas and receivers that are connected by up to 100 m of underground coaxial cables, using conventional lightning protection electronics. We expect that individual antennas are only damaged when a lightning stroke impacts within four meters distance. The estimated induced currents, voltages and charges using simplified electro magnetic modeling indicate that the protection measures avoid induction damage to the cables and connected receivers.