Giuseppe Colombo was an Italian mathematician and ground-breaking theorist in orbital mechanics at the University of Padua. He proposed space tethers for linking satellites together, was one of the initiators of the ESA (European Space Agency) Giotto mission to Halley's Comet, and suggested how to put a spacecraft into an orbit that would bring it back repeatedly to the planet Mercury. His calculations were used to determine the course taken by Mariner 10 in 1974–1975, which enabled the probe to make three passes of the innermost planet. Colombo also explained, as an unsuspected resonance, Mercury's habit of rotating three times for every two revolutions of the Sun. His name has been given to ESA's own proposed mission to Mercury, BepiColombo.