Passive doppler navigation system using measurements of ship-based millimeter-wave radiometer

The paper describes a concept of new type shipborne Doppler navigation system utilizing microwave spectroscopy of the Earth’s atmosphere. It is a completely passive system that measures emission spectra of gas radiothermal radiation surrounding a planet. Narrowband spectrum of a gas molecule consists of sharply defined frequency lines that can be shifted because of relative motion of the observer. The physical properties of gases emission, principles of microwave radiometry, typical instrument and observation modes are analyzed. The over- all performance characteristics of microwave Doppler-spectro-radiometeric navigation system and its accuracy are outlined. It is shown that such system can provide information on vector of actual speed and play role in measuring present position, course and distance to destination. Velocity measuring errors essentially depends on Doppler and pressure broadening of transitional emission line of a gas and on spectrometer resolution. Known microwave spectroscopy technique and well-studied gas lines can provide almost the same accuracy of navigation as the Doppler speed log. But in contrast to popular methods of speed measurements current research shows power-efficient, simple and totally covered thechnique of ship navigation that can be further developed.