BBC: Measuring the exact locations of bodies in the solar system has been difficult. But such measurements are important for determining the orbits of the planets and calculating the correct trajectories for spacecraft. Dayton Jones of NASA's Jet Propulsion Laboratory and his colleagues used the Very Long Baseline Array, a collection of 10 radio telescopes spread from Hawaii to the Virgin Islands, to precisely locate the Cassini spacecraft relative to a grid of distant quasars. With that measurement, calculating Saturn's position was easy because Cassini is in orbit at a known distance around the planet. The best previous measurements of Saturn's location were 20 times less precise.