Monday, 10 February 2003: 11:45 AM
Upper Air Rawinsonde Observation Using an Integrated GPS/RDF Receiving System
The advent of GPS wind-finding technology in the 1990ís divided the world of upper air sounding into two camps: GPS systems transmitting in the 403 MHz band and radio direction finding (RDF) systems using the 1680 MHz band. Advantages of 403 GPS systems are a lower initial investment for ground stations and the relative ease of use. Negatives to date are a high failure rate due to GPS dropouts, and the high cost of disposables due to the high cost of the GPS receiver. These factors have raised the cost of GPS rawinsonde operations, contributing to a decline in active sites and a reduction in upper air data available for meteorologists and climatologists. Two new tracking systems that operate in the RDF, GPS or GPS/RDF modes are presented. The combined GPS/RDF mode of operation significantly reduces flight failures by providing redundant RDF wind-finding data when GPS data is lost. In addition, these new tracking systems offer users the opportunity to fly a low-cost RDF radiosonde instead of a GPS radiosonde whenever local upper air conditions are favorable, e.g., low winds. The benefits of being able to use a GPS radiosonde or one without GPS (RDF mode of operation) are presented in a cost tradeoff analysis. By eliminating lost flights and allowing a mix of high and low cost radiosondes, the life cycle cost of upper-air observation stations can be reduced, while giving users maximum flexibility and performance.