Abstract A Transition Radiation Detector (TRD), has been built to be used as charged particle identifier in satellite born apparatus. Originally conceived to be used in the PAMELA telescope, this TRD has been qualified for space as well. The compact design and the low power consumption make this detector suitable to be used in space researches in which identification is required for particle of relativistic energies (i.e. with Lorentz factor ( γ ) > 1000 . In this TRD, carbon fibers are used as radiator material, and 1024 straw tubes as sensitive detectors. All components are piled up in nine sensitive layers of radiators and straws working in proportional mode using a Xe – CO 2 gas mixture. The detector characteristics will be described along with its performances studied having exposed the detector to both cosmic rays and particle beams at CERN.