Abstract
We propose to observe the ``clocked buster'' GS1826-24 simultaneously with RXTE, optical and near-IR (NIR) telescopes. The primary objective is to study simultaneous X-ray/optical/NIR bursts in detail by measuring the delay time and smearing from the high quality lightcurves. Together with the color information during the bursts, we will provide constraints on the geometry and physical properties of the system. The high quality simultaneous data also allow a study of correlated variability and phase-resolved X-ray timing and spectral behaviors of the persistent flux.