Airborne Second Generation Precipitation Radar
The APR-2 is a dual-frequency (13 GHz & 35 GHz), Doppler, dual-polarization radar system (APR3 has added W-Band radar capability to APR2). It has a downward looking antenna that performs cross track scans, covering a swath that is +/- 25 to each side of the aircraft path. Additional features include: simultaneous dual-frequency, matched beam operation at 13.4 and 35.6 GHz (same as GPM Dual-Frequency Precipitation Radar), simultaneous measurement of both like- and cross-polarized signals at both frequencies, Doppler operation, and real-time pulse compression (calibrated reflectivity data can be produced for large areas in the field during flight, if necessary).
More technical details on the APR-2 can be found in Sadowy et al. (2003)