Continuous measurement and monitoring of Eb/No ratio received during a remote sensing satellite-pass at a multi-mission ground station

Remote sensing satellites transmit imaging data using PSK modulation schemes with very wide range of data rates. Continuous on-line monitoring and measurement of energy-per-bit to noise-density (E_b/N_o) ratios received during a satellite-pass become essential to perform the real time data quality analysis [Jain, P.K. et al., March 2003]. The real time estimation of E_b/N_o is also useful during the initial phase of the mission, i.e.. immediately after the launch of the satellite and switching on the payloads as the level fluctuations, if any, can be analyzed properly. Besides, the link analysis and practical assessment of the link margins are essential to optimize the receive chain parameters for real time compatibility [Limaye, U.D., October 1993]. This paper describes various methods to carry out this measurement with an emphasis on a unique technique developed in National Remote Sensing Agency. Dept. of Space. Govt. of India, Hyderabad. This technique uses a long loop PLL carrier recovery circuit of a multi-mission PSK demodulator and is found superior over other methods on several counts. The method has been tested for various PSK schemes at different data rates and implemented successfully in a remote sensing satellite ground station.