From the ARRL web site, dated 7/31/10:
The ARRL minor planet/asteroid (31531) is approximately 2.5-4 miles (3-7 km) long. It orbits the Sun at a distance of 2.7 Astronomical Units (AU). It is currently located near the boundary of the constellations Scorpio and Libra and is about 2.1 AU distant from the Earth. It takes (31531) ARRL almost five years to orbit the Sun.
For the full story, go here:
http://www.arrl.org/news/it-s-a-bird-it-s-a-plane-no-it-s-an-asteroid-asteroid-31531-arrl-to-be-exactThe ultimate Field Day location: