The STK consists of multiple layers of silicon micro-strip detectors with interleaving tungsten converter plates. STK tracks the direction of gamma-rays by their conversion to charged particles in the tungsten plates, then tracking the particles through the instrument. STK has 6 tracking planes, each with two layers in X and Y planes, orthogonal to the instrument pointing. Cumulatively, this makes a sensor with 0.2° angular resolution at 10 GeV and the total silicon area is roughly 7 m2.