Three-body model fits to Arecibo and Goldstone radar data reveal the nature of two near-Earth asteroid triples .
Triple-asteroid system 2001 SN263 is characterized by a primary of \sim 10 ^ { 13 } kg , an inner satellite \sim 1 \% as massive orbiting at \sim 3 primary radii in \sim 0.7 days , and an outer satellite \sim 2.5 \% as massive orbiting at \sim 13 primary radii in \sim 6.2 days .
1994 CC is a smaller system with a primary of mass \sim 2.6 \times 10 ^ { 11 } kg and two satellites \sim 2 \% and \lesssim 1 \% as massive orbiting at distances of \sim 5.5 and \sim 19.5 primary radii .
Their orbital periods are \sim 1.2 and \sim 8.4 days .
Examination of resonant arguments shows that the satellites are not currently in a mean-motion resonance .
Precession of the apses and nodes are detected in both systems ( 2001 SN263 inner body : d \varpi / dt \sim 1.1 deg/day , 1994 CC inner body : d \varpi / dt \sim -0.2 deg/day ) , which is in agreement with analytical predictions of the secular evolution due to mutually interacting orbits and primary oblateness .
Nonzero mutual inclinations between the orbital planes of the satellites provide the best fits to the data in both systems ( 2001 SN263 : \sim 14 degrees , 1994 CC : \sim 16 degrees ) .
Our best-fit orbits are consistent with nearly circular motion , except for 1994 CC ’ s outer satellite which has an eccentric orbit of e \sim 0.19 .
We examine several processes that can generate the observed eccentricity and inclinations , including the Kozai and evection resonances , past mean-motion resonance crossings , and close encounters with terrestrial planets .
In particular , we find that close planetary encounters can easily excite the eccentricities and mutual inclinations of the satellites ’ orbits to the currently observed values .