On the utilization of ionospheric diagnostics in the single-site location of HF emitters

The Naval Research Laboratory conducted an experiment during the latter half of calendar year 1982 which dealt with the problem of HF Single-Site-Location (SSL) as envisioned for the U.S. Army Rear Echelon HF Comint System (RECS). This experiment was conducted for the purpose of certifying a baseline SSL system and the test was identified simply as the SSL-BCT (Baseline Certification Test). Two specific approaches to SSL were examined during the experiment which was conducted from a base station located at Fort Ord, California. For the most part the desire was to examine two competing SSL techniques in an environment which simulated an actual operational situation, viz., a single-blind experiment. As control, however, there was a period (Phase 1) during which each competing technique was calibrated against known HF emitters. Measurements were made using a variety of emitters located at short, medium, and moderately long ranges to the east of Fort Ord. The results of these tests, in which systems developed by Southwest Research Institute and Technology for Communications International were exercised, have not yet been released. However, generalized conclusions have been reached. To be assured that the ionospheric channel was properly specified, the SSL-BCT test range was instrumented as fully as possible. Oblique ionosondes, vertical incidence ionosondes, Faraday rotation polarimeters, and satellite-borne topside sounders were used for the purpose of ionospheric specification. This paper describes the general SSL-BCT approach and the type of results which were obtained but it emphasizes the various approaches to ionospheric specification required for optimum SSL operation.