Bill Dent is retired System Astronomer at the ALMA Observatory in Chile.
Bill talked about the ALMA radio observatory in Chile. This is an array of 66 steerable microwave dishes, the largest and most powerful array in the world, operating together at frequencies of 30-1000GHz in the Atacama desert, one of the driest places on earth (necessary for microwave astronomy) and at an altitude where supplementary breathing oxygen is required! He described the site, some of the technical challenges of observing at >100GHz, and showed some of the astronomical results.
Many thanks to Bill, shown here with his niece, for a most interesting talk about the ALMA Observatory in Chile.