| Description: | The conducting groundplane on which a LOFAR antenna is placed has two functions: to protect it from radio emission from the "hot" (300 K) ground, and to improve its sensitivity and directivity. For each dipole, the conducting sheet "creates" a virtual dipole at its mirror position w.r.t. the plane. For a particular wavelength, this doubles the sensitivity in the zenith direction. The response is different for other wavelengths and directions.
Although the response of (arrays of) LOFAR antennas is understood in principle, there are various complicating factors, whose effects are difficult to predict in detail. Therefore, it will take some time before we have fully mastered them in practice. But the effort is worth it, because this technology is the way forward to the next generation of very large radio telescopes.
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