Improved radar sensitivity through limited sector scanning: The DCAS approach

Abstract

Distributed Collaborative Adaptive Sensing (DCAS) is being developed to provide solutions to many existing limitations of operational weather radar. DCAS makes use of large numbers of distributed short-range (30 km) radar to monitor the first 3 km of the Earth’s atmosphere. DCAS includes the ability to rapidly adjust individual radar operating parameters in a collaborative manner. Included in these parameters is the ability to adjust individual node volume coverage pattern (VCP) in accordance with meteorological events. By adjusting VCP to maximize time on target measurement precision may be improved (McLaughlin et al. 2005). DCAS radars are operated as a network and collaboratively make use of neighboring radar capabilities in order to improve data quality. In this paper we examine the expected theoretical improvement in reflectivity measurement by employing limited sector scanning. Operational radars employ VCPs that include full azimuth rotations as well as multiple tilts in elevation. During a storm event, targets of interest may be located in a limited sector of the full VCP. By limiting the scanning sector, time which would have been spent completing a full volume scan, including volume of limited data utility, is spent observing the targets of interest. By dynamically adjusting a DCAS radar’s VCP to the limited sector of interest, measurement precision may be increased by increasing dwell time. Sensitivity may be improved for a given measurement precision by decreasing the required signal to noise ratio. Dynamic adjustment of a radar’s VCP will require high speed beam scanning via high torque mechanical pedestals or electronic beam scanning. The initial DCAS testbed radars have the capability to scan in azimuth at 120 deg/s and elevation at 30 deg/s (Juyent et al. 2005). Such high scan systems will enable the interlacing of general full volume scans with higher precision limited sector scans. This paper will analyze the theoretical improvements from limited sector scanning in detail. A review of fading theory will be presented followed by both single and multiple node limited sector scanning.