Goldstone Radar Observations Planning: Comet C/2013 UQ4 (Catalina)
2013 UQ4 was discovered by the Catalina Sky Survey on 2013 October 23 and it immediately generated considerable
scientific interest due to its large size (absolute magnitude of 12.8) and very unusual retrograde, comet-like orbit
(a = 60.4 AU, e = 0.98, i = 145.3 deg, q = 1.1 AU, Q = 119.7 AU, P = 469.0 years).
This object did not show any cometary activity at the time of discovery, but images from May 7, 2014 from
the iTelescope Observatory (station Q62) in Siding Spring, Australia, show a coma, and consequently 2013 UQ4 has been classified
as a comet by the Minor Planet Center: C/2013 UQ4 (Catalina).
Similar to other cometary nuclei, 2013 UQ4 appears to be optically dark (Binzel et al., 2013) with a ~4%
optical albedo. Size estimates are all over the map from 7 - 23 km. Below we adopt D = 23.5 km from
thermal modeling by A. K. Mainzer using WISE data obtained before this object showed cometary activity.
The rotational period for 2013 UQ4 is not known at this time, but based on the current knowledge of the asteroids
and comets in this size range, the period is likely longer than 6 hours.