2008 GS3 is Aten-type Near Earth Asteroid that has been discovered by the Lincoln Laboratory ETS Sky Survey (MPC #704) on 2008, April 7.30; we performed its follow-up from the Remanzacco Observatory on 2008, April 7.9, while it was labeled as "BJ81650" in the NEO-CP webpage. At the beginning, it didn't show up in stackings, very likely because of the uncertainty of its ephemerids (the stacking we did was performed according the "best guess" preliminary speed and PA available at the moment).
On 2008 April 9.5, the object was still listed in the NEO-CP, but its ephemerids were considerably improved due to the follow-up astrometry produced by several observers. Then we re-stacked our original frames of the 7-8 April night with the new speed and PA, and we find it!
According to the preliminary orbital elements available at Minor Planet Center database, 2008 GS3 is a rock with an estimated diameter of nearly 100 meters, orbiting the Sun every 9.5 months. At perihelion it reaches at almost 80 Million Km from our star, between the orbits of Mercury and Venus, while at aphelion it approaches the Earth's orbit. When we imaged it, the asteroid was at 25 Million Km from our planet, moving at nearly 7.3 arcsec/min in Virgo, with a magnitude of nearly R~19.
Giovanni Sostero & Ernesto Guido