The need for a suitable method for obtaining upper air wind speed and direction data over the ocean areas of the world has long been recognized. The recent development of windfinding systems utilizing the LORAN-C and Omega navigational aids for locating the balloon-borne receiver with reference to a horizontal plane has greatly enhanced the possibility of satisfying this need. Although the Omega navigational system is being designed for global coverage, the difficulty in recovering the Omega data in regions of high sferics activity presents a formidable obstacle to operation in the tropical regimes.
An Omega windfinding system has been designed to produce upper-air wind speed and direction within GARP Atlantic Tropical Experiment (GATE) accuracy requirements, i.e., winds to 1 m sec−1 with vertical resolution to at least 1 km, preferably 1/2 km, in regions of high sferics activity. The system was developed and fabricated by personnel of the National Aeronautics and Space Administration, Mississippi Test Facility (MTF), as a component of the Upper Air Meteorological System (UAM) of the Portable Data Acquisition System (PODAS) built for the National Oceanic and Atmospheric Administration's GATE Systems Engineering Office.
This paper presents illustrations of high sferics content Omega data and a discussion of techniques used to recover the true Omega phase data; describes the design and operation of the hardware preprocessor developed to extract the true Omega phase data from the received signals; describes the software developed to compute upper-air winds from high sferics content data; outlines the program conducted to establish the validity of the system; and presents results of upper-air wind comparisons made with LORAN-C and FPS-FPQ-6 radar systems.
