A position sensitive radiation spectrometer for identifying, quantifying, and locating a radioactive source in a target. One of the two power supply lines is connected with an externally located main power source, and the other power supply line is connected with an externally located backup power source. The data streams are synchronized using a navigation file, which comprises descriptors pointing to parts of said data streams, wherein said descriptors define the arrangement in time for said data streams by means of data sub stream paths.