Jupiter to several seconds, and short bursts (or S-bursts) that had a duration of less than a hundredth of a second. Scientists discovered that there were three forms of radio signals transmitted from Jupiter. Since 1973 a number of automated spacecraft have visited Jupiter, most notably the "Pioneer 10" space probe, the first spacecraft to get close enough to Jupiter to send back revelations about the properties and phenomena of the Solar System's largest planet. Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the
Jupiter 2000, the "Cassini" probe flew by Jupiter on its way to Saturn, and provided some of the highest-resolution images ever made of the planet. The "New Horizons" probe flew by Jupiter for a gravity assist en route to Pluto. Its closest approach was on February 28, 2007. The probe's cameras measured plasma output from volcanoes on Io and studied all four Galilean moons in detail, as well as making long-distance observations of the outer moons Himalia and Elara. Imaging of the Jovian system began September 4, 2006. The first spacecraft to orbit Jupiter was the "Galileo" probe, which entered orbit