Hello List! Just got a link to a fresh release from ESA: They dedicate a H MASER at Estec to steer it with Pulsar measurements from 5 european radio telescopes and compare it to the adjacent ESA UTC lab, which equipped with 3 H MASER and 3 Cs clocks. http://www.esa.int/Our_Activities/Navigation/ESA_sets_clock_by_distant_spinning_stars Greetings HD