Experimental investigation of aeronautical and maritime communications and surveillance using satellites
- Paper ID
IAF-73-19
- author
- company
Corporate Research and Development, General Electric Group
- country
U.S.A.
- year
1973
- abstract
Five years of experiments with the National Aeronautics and Space Administration’s ATS-1, ATS-3 and ATS-5 satellites have shown that range measurements from geostationary satellites may provide 0.1 nmi*, 1 sigma position fix accuracy over large areas of the earth at Lb and. Better than 1 nmi, 1 sigma could be achieved at VHP. Sponsorship and funding support were provided by NASA under contract NAS5-11634. The ranging measurements can be made by the insertion of ranging codes in a digital communications data stream. The duration of the ranging signals is a small fraction of a second so that time occupancy for ranging with the communication channels is very short compared to most communication messages. The ranging capability can be added to the user’s digital communications equipment for a small cost increment. Every factor affecting communications reliability, ranging precision, and position fix accuracy is measured in the experimental program at VHP and L-band. Means to rectify the causes of bias errors are being tested. The tone-code ranging technique has been thoroughly tested in a series of experiments that started in 1968^1,2) Experiments using the VHP transponders of ATS-1 and ATS-3, approximately 149 MHz up to the satellites, and 135 MHz down from the satellites, employ the voice bandwidth of ordinary mobile communications. Ranging precision of approximately 45 m and position fix accuracies better than 1 nmi are achieved. The tests were expanded in 1971 to include ranging through the L-band transponder of the ATS-5 satellite at frequencies approximately 1651 up to the satellite and 1550 MHz down, with approximately a 10kHz modulating frequency. Ranging precision better than 15 m is achieved and position fix precision is approximately 0.1 nmi, 1 sigma, with one range measurement at VHP and one at L-band. The tone-code ranging technique developed into an entirely digital process which is fully compatible with digital communications.