History of radar for various purposes; on the Shuttle Radar Topography Mission, the entire planet was mapped at a 30-m resolution. The Jodrell Bank Observatory, an operation of the University of Manchester in Britain, was originally started by Bernard Lovell to be a radar astronomy facility. It initially used a war-surplus GL-II radar system operating at 71 MHz (4.2 m). The first observations were of ionized trails in the Geminids meteor shower during December 1945. While the facility soon evolved to become the third largest radio observatory in the world, some radar astronomy continued. The largest (250-ft or 76-m in diameter) of their
December Hydrids (December 4–15), and the Ursids (December 17-to December 25/26, peaking around December 22). "This list does not necessarily imply either official status or general observance." Last Week of November: November 25 – December 1 First Sunday: December 2 Fourth Sunday before Christmas Day: December 2 First Monday in December and following 7 days: December 3-9 First Friday: December 7 Sunday two weeks before Christmas: December 9 Second Monday: December 10 December 15, unless the date falls on a Sunday, then December 16: December 15 Second-final Sunday before Christmas Day: December 16 Thursday before Christmas: December 20 Winter Solstice: December