ATS-6 European L-Band Aeronautical Experiments

Abstract

This paper describes the European experiments and test results obtained in L-band (1550-1650 MHz),using the NASA ATS-6 satellite, to conduct communication and navigation tests over the North Atlantic thus assisting in the definition of modulation techniques to be used with an Aeronautical Satellite System, AEROSAT. The experiments conducted by ESA and some of its member states covered voice, data transmission and ranging measurements. The tests were performed on board a Comet IV aircraft equipped with a slot dipole array antenna, especially designed to operate within the coverage required in the AEROSAT MOU (Memorandum of Understanding for the AEROSAT programme signed by Europe (ESA), the USA (FAA) and Canada (DoT) in August 1974. The voice tests compared DELTA-PSK with adaptive NBFM using test tapes consisting of logatoms, SCIM sequences, and PB word lists. An investigation of multipath noise effects on the PSK data transmission system was carried out and led to the general conclusion that this problem is a serious one for coherent demodulators. The DECPSK system tested exhibited a strong tendency towards a Rayleigh channel BER situation at low antenna signal to multipath interference ratios. The ranging results show the feasibility of achieving standard deviations of range of around 500-600 m for the PLACE tone system with its rather short integration time of 120 ms, and 100 m for the DIOSCURES pseudo random coded system operated on a CW basis.