After a major disaster caused by a meteorite falling in Eastern Italy in 2077, the government of Earth sets up the Spaceguard system as an early warning of arrivals from deep space. Rama is an alien star ship, initially mistaken for an asteroid categorised as "31/439". It is detected by astronomers in the year 2130 while still outside the orbit of Jupiter. The object's speed (100,000 km/h) and the angle of its trajectory clearly indicate that this is not an object on a long orbit around our sun; it comes from interstellar space. Astronomers' interest is further piqued when they realise that this asteroid not only has an extremely rapid rotation period of 4 minutes, but it is exceptionally large. It is subsequently renamed Rama after the Hindu god and an unmanned space probe dubbed Sita is launched from the Mars moon Phobos to intercept and photograph the object. The resulting images taken during its rapid flyby reveal that Rama is a perfect cylinder, 20 kilometres (12 mi) in diameter and 54 kilometres (34 mi) long, made of a completely featureless material, making this humankind's first encounter with an alien space ship.