ADS-B over Satellite Coherent detection of weak Mode-S signals from Low Earth Orbit

Abstract

The world's first ADS-B over Satellite (AOS) In-Orbit Demonstrator (IOD) within ESA PROBA-V mission is operational since May 2013 and has successfully validated the principle of detecting weak Mode-S transponder transmissions from a Low Earth Orbit (LEO). A special feature was included in the receiver's firmware that allows to upload new configurations and to activate these by remote access. During mission runtime so far, this has been successfully tested several times. In the meanwhile an improved Mode-S correlation mechanism was developed that benefits from the phase coherence of the pulse train from the first Mode-S preamble pulse to the fifth format bit. In lab tests it could be shown that the telegram detection rate increased significantly. Moreover, by generating and saving "Low-Confidence Bits" for the 112 Mode-S data bits in DF17, there is an additional chance to increase the success rate for error-free demodulation of the telegram in postprocessing. The improvement on ADS-B data from space in comparison with the results gained with the non-coherent approach will be shown.