Observations of the Asteroid by the Goldstone and Arecibo radio telescopes have been scheduled for 22-27th and 25-29th August respectively.
Almost nothing is known about its physical properties, but its absolute magnitude of 17.9 suggests a diameter of roughly 800 meters if it has an albedo representative of the most common compositional class of asteroids. This object has an unusual orbit suggesting that it may be an inactive comet nucleus. Its semimajor axis (3.2 AU) is deep in the outer asteroid belt, where most objects tend to be optically dark, and its aphelion distance is beyond the orbit of Jupiter. If this object has a dark optical albedo, then its diameter may be much larger than 800 meters, possibly as much as 1500 meters, and thus a significantly stronger radar target than our signal-to-noise estimates below suggest. Furthermore, only a few inactive comet candidates have been observed by radar, so this is an important opportunity. Recent research has shown that some outer main-belt asteroids intermittently show cometary activity (such as the formation of a coma) and may represent a class of objects transitional between asteroids and comets. Source
The 720 - 1600 metre wide asteroid 2009 KC3 will make a close pass (18.8 Lunar Distances, 0.0484 AU), travelling at 11.80 km/s, to the Earth-Moon system on the 24th August, 2009.
Orbital elements: 2009 KC3 PHA, Earth MOID = 0.0098 AU Epoch 2009 June 18.0 TT = JDT 2455000.5 MPC M 350.32405 (2000.0) P Q n 0.17306486 Peri. 337.45864 +0.73778502 +0.67240712 a 3.1890656 Node 339.91563 -0.58989912 +0.59936306 e 0.6977259 Incl. 9.98013 -0.32816505 +0.43431854 P 5.70 H 17.9 G 0.15 U 7