The U.S. Air Force operates a network of tethered lighter-than-air aircraft (aerostats) along the southern U.S. border and in Puerto Rico. Normally stationed at altitudes of approximately 3 km, the aerostats provide platforms on which surveillance radars are positioned to monitor U.S. airspace in support of national security. The Tethered Aerostat Radar Systems (TARS), like all aircraft, can only operate safely within certain atmospheric conditions. In particular the TARS are susceptible to damage during episodes of high turbulence that is typically associated with wind shear. Over the past ten years this and other weather events have been responsible for the damage and loss of several aerostat systems and their associated radars. Along with the loss of surveillance data, safety is also of prime concern during these weather events.

In response to a desire for enhanced upper-air monitoring for the TARS, the U.S. Air Force requested National Oceanic and Atmospheric Administration°¦s (NOAA) Environmental Technology Laboratory (ETL) to jointly develop with industry, a reduced-aperture tropospheric wind profiling radar in support of the aerostat program. The resulting radar is a combination of Vaisala°¦s commercial LAP„¥ technology, NOAA ETL°¦s advanced signal processing software (SPS), and other carefully selected commercial-off-the-shelf subassemblies.

The new system operates at 449 MHz, has a peak-transmitted power of 2 kW and uses a coaxial-collinear antenna array with an aperture of 54 square meters. This topology was developed to meet the Air Force°¦s data recovery needs. The system offers a reduced-aperture antenna, less output power, and lower manufacturing, maintenance and deployment costs than is traditionally associated with tropospheric wind profiler systems operating within this frequency band. The first reduced-aperture 449 MHz wind profiler was installed at an operational aerostat site in Ft. Huachuca, AZ, USA during the fall of 2001. Since its deployment, the radar has undergone verification and validation tests as well as integration with other operational flight instrumentation hardware.

The presentation will include a discussion of the new wind profiler topology and the design characteristics that will provide reliable and unattended operation. Statistics for system performance, data recovery and data quality, as compared to radiosonde data, will be presented.