ON SEPTEMBER 11th, around 1.2bn kilometres from Earth, Cassini, a robotic spacecraft that has been orbiting Saturn for 13 years, will make a final flypast of Titan, Saturn’s biggest moon. Since April the NASA craft has been conducting a series of long, looping orbits that take it between Saturn itself and the innermost of the planet’s famous rings. After passing Titan, Cassini will dive back towards Saturn, but this time, it will not return. On September 15th, at about 1pm London time, it will kiss the outer edges of Saturn’s atmosphere and begin to tumble, losing contact with Earth. A few minutes later it will burn up as a shooting star, bringing down the curtain on a long and dramatic mission to an under-explored corner of the solar system.