of binary near-Earth asteroid (175706) 1996 FG3, that is consistent with the theory of Jacobson and Scheeres (2011a) of that synchronous binary asteroids are in a state of stable equilibrium between binary YORP (BYORP) effect (which is a secular change of the mutual orbit of the components of a binary asteroid due to the emission of thermal radiation from asymmetric shapes of the components) and mutual body tides. In this paper, we present a comprehensive analysis of mutual orbit drifts in two well-observed binary near-Earth asteroids (NEAs).

The NEA (66391) Moshup = 1999 KW4 was discovered by Lincoln Near-Earth Asteroid Research in Socorro, New Mexico, on 1999 May 20. Its binary nature was revealed by Benner et al. (2001). We obtained thorough photometric observations for it in six apparitions from 2000 to 2019. Since the asteroid was named only recently and its original designation 1999 KW4 is well-known to the asteroid science community, we use it throughout this paper.

The NEA (88710) 2001 SL9 was discovered by Near-Earth Asteroid Tracking at Palomar on 2001 September 18. Its binary nature was revealed by Pravec et al. (2001). We obtained thorough photometric observations for it in five apparitions from 2001 to 2015.

