  The Kepler-9 system harbors three known transiting planets. The system holds
significant interest for several reasons. First, the outer two planets exhibit
a period ratio that is close to a 2:1 orbital commensurability, with attendant
dynamical consequences. Second, both planets lie in the planetary mass "desert"
that is generally associated with the rapid gas agglomeration phase of the core
accretion process. Third, there exist attractive prospects for accurately
measuring both the sky-projected stellar spin-orbit angles as well as the
mutual orbital inclination between the planets in the system. Following the
original \textit{Kepler} detection announcement in 2010, the initially reported
orbital ephemerides for Kepler-9~b and c have degraded significantly, due to
the limited time base-line of observations on which the discovery of the system
rested. Here, we report new ground-based photometric observations and extensive
dynamical modeling of the system. These efforts allow us to photometrically
recover the transit of Kepler-9~b, and thereby greatly improve the predictions
for upcoming transit mid-times. Accurate ephemerides of this system are
important in order to confidently schedule follow-up observations of this
system, for both in-transit Doppler measurements as well as for atmospheric
transmission spectra taken during transit.
