Smart-µg™ is a customized optical tracking system produced by BTS (Italy,), qualified for parabolic flights (transient microgravity). It is composed by three main parts: (i) a recording/tracking system; (ii) a PC; (iii) CCD infrared tracking cameras. Cameras have with a CCD detector sensible to infrared and a LED enlighter emitting at 850 nm. The highest sample frequency is 120 Hz. The system works with passive plastic retroreflective markers, which reflect the near-infrared light allowing the cameras to detect their 2D projection on the sensor planes. From the calibration parameters of each camera and the marker 2D coordinates coming from at least two cameras sensors at the same time instant, the system algorithm is able to provide the absolute 3D position of each marker, by collinearity equations. Then, the tracking procedure is performed by the operator, using a system-specific software (SmartTracker®), in order to associate the 3D reconstructed data with the markers model for all acquired frames.