Detection and localization of lost objects by SAR technique

Containers and pallets are often lost from ships. A system based on a micro satellite weighting less than 100 kg, embracing a small SAR (Synthetic Aperture Radar) sensor; a transponder installed in the container and one or more ground stations is described. When a container drops in the water a floating housing is unhooked and the internal transponder is switched-on. Initially it works in a low power consumption status and then, when activated by the small satellite beacon, starts full power operations. The azimuth localization is performed by a synthetic aperture or Doppler analysis processing. In the range direction a short pulse is used. The radar transmitted frequency is shifted inside the transponder, maintaining the coherence. This avoids any problem of time ambiguities in the radar because the receiver chain operates at a different frequency from the transmitter. The micro satellite should be equipped with GPS system for determining its position along the orbit. The received signals are preprocessed on board and then transmitted to the satellite control station. A requirement of four/five days can be met by a single satellite while up to four's are needed for one day revisit time. This paper deals with the description of such innovative system, its dimensioning and possible implementation solutions for the micro satellite radar and the electronics contained into the transponder.