Real-Time In Situ Signal-To-Noise Ratio Estimation for the Assessment of Operational Communications Links

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the Lead Center for NASA's scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA's institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types: • TECHNICAL PUBLICATION. Reports of completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NASA's counterpart of peer-reviewed formal professional papers but has less stringent limitations on manuscript length and extent of graphic presentations. • TECHNICAL MEMORANDUM. Scientific and technical findings that are preliminary or of specialized interest, e.g., quick release reports, working papers, and bibliographies that contain minimal annotation. Does not contain extensive analysis. • CONTRACTOR REPORT. Scientific and technical findings by NASA-sponsored contractors and grantees. • TECHNICAL TRANSLATION. English-language translations of foreign scientific and technical material pertinent to NASA's mission. Specialized services that complement the STI Program Office's diverse offerings include creating custom thesauri, building customized data bases, organizing and publishing research results. .. even providing videos. INTRODUCTION The assessment of the propagation conditions that prevail on a communications link, whether it is a point-to-point terrestrial link or an earth-space link, is of vital importance for the optimal operation of the link. The significant indicator of the communications quality of the link is, of course, the signal-to-noise ratio (SNR) g. If the value of this quantity goes below a certain given threshold due, for example, to atmospheric conditions such as rain, the bit error rate on the link becomes unacceptable for reliable communications integrity. Knowledge of the dynamic behavior of g is thus essential for the optimal implementation of procedures to mitigate the further degradation of g. In many instances, a separate propagation receiver is employed to acquire an associated signal transmitted by a beacon on the communications satellite. Measurement of the …