Lopes - Recent Results And Open Questions On The Radio Detection Of Air Showers

LOPES a._ digital antenna. array operating for approximately 10 years u 1 spring- 2013 at the Karlsruhtt Institute of Technology (KIT). Triggered. lty the co-loca,ted KASCADE-Grande air-shower experiment, it, measured. the ra,dio signal of around. 1.000 cosmic,ir showers with energies E 101' eV in an effective band. of 7z1-1\41.-Iz. Using n erometric technique of cross-correlation beamforming, LOPES could reconstruct the shower direction with an accuracy E greater than or similar to 10(17), the shower energy with a -precision < 20%, and the atmospheric depth of the shower maximum, X, x, witti a, precision < 95 gicm2. In particular reconstruction of the shower ma,ximum. suffers from significant measurement uncertainties due to the radio-loud environment of (he site. This a,rticle summarizes our latest results on the, reconstruction of the shower maximum, using two independent methods: the steepness of the hyperbolic radio wavefront and the slope of the lateral distribution of the radio amplitude. Moreover, we show vectorial measurements of the electric field with the tripole antennas of the latest LOPES setup. Finally, we discuss open questions as well as the potential impa,ct of the lessons lea,rned at, LOPES for future antenna, arra,ys.