Experimental astroparticle physicist developing radio-based detection of ultra-high-energy cosmic rays. Directions: (1) HAWC — high-altitude water Cherenkov detector for gamma-ray and cosmic ray sensing; (2) IceTop surface array at IceCube for cosmic ray composition at the knee; (3) radio detection of cosmic-ray-induced air showers (Askaryan emission) as a technique for large-scale UHE cosmic ray sensing. Enrico Fermi Institute member.