On 16 August 2003, Illapa made a close approach to Earth of 0.025037 AU (3,750,000 km; 2,330,000 mi).[4]
Physical characteristics
Illapa has an estimated diameter of 0.8 to 1.8 kilometers for an assumed geometric albedo between 0.20 and 0.04.[2] For an assumed albedo of 0.057, which is typical for carbonaceous C-type asteroids, and an absolute magnitude of 17.9,[1] the asteroid has a calculated mean diameter of 1.5 kilometers. The body has a short rotation period of 2.6556 hours.[1]