APAR Scanning Requirements and Strategies

The Airborne Phased Array Radar (APAR) is an advanced atmospheric system which is currently being developed at NSF-NCAR. It will replace the expired X-band Electra Doppler radar (ELDORA). The ELDORA radar scanned the atmosphere using a rotating plate to direct the transmit pulses in fore- and aft-pointing cones geometry. APAR will operate on a completely different principle using electronic beam steering with 4 C-band Active Electronically Scanned Arrays (AESAs): one on each side of the aircraft, one on top and one on the bottom. Here we will focus on the scanning requirements for the side AESAs. The typical strategy will be to have 3 scans for one cycle: 1) Doppler 2) polarization and 3) surveillance. This set of scans needs to be completed so that a resolution requirement of 300 m is met along the flight path direction. If the aircraft speed is 120 m s^-1, this mean that the scan cycle needs to be completed in 2.5 seconds. Even with electronic scan agility, it will be challenging to meet desired requirements of resolution, sensitivity, measurement error, unambiguous range and Nyquist velocity. This talk, then, examines and defines some of the scanning strategies to meet these requirements.