Titan was examined by both "Voyager 1" and "2" in 1980 and 1981, respectively. "Voyager 1"'s trajectory was designed to provide an optimized Titan flyby, during which the spacecraft was able to determine the density, composition, and temperature of the atmosphere, and obtain a precise measurement of Titan's mass. Atmospheric haze prevented direct imaging of the surface, though in 2004 intensive digital processing of images taken through "Voyager 1"'s orange filter did reveal hints of the light and dark features now known as Xanadu and Shangri-la, which had been observed in the infrared by the Hubble Space Telescope. "Voyager 2", which would have been diverted to perform the Titan flyby if "Voyager 1" had been unable to, did not pass near Titan and continued on to Uranus and Neptune.