PRISM

PPIS can also measure the surface backscatter at HH, HV, VH, and VV polarisations. The system can be configured to operate independently at 440 MHz and 860 MHz, or can be operated in interleaved mode with simultaneous measurements at both frequencies. The PPIS is composed of two 2x2 patch array antennas operating at 860 MHz, inclined at an angle of 30° from the horizontal to either side of the aircraft, and a single electronically beam steered 4x4 patch array antenna operating at 440 MHz. These antennas obtain push broom imagery over a cross track swath of +/-45°. Both antennas are able to transmit and receive at V and H polarisations. The antenna gain is 9 dBi for 440 MHz and 10dBi for 860 MHz. In the cross-track direction, the antenna gain is within 2.5 dB of the maximum gain between 15° and 45°. The peak transmit power at the output of the RF unit is 20 W for 440 MHz and 14 W for 860 MHz. At the start and end of PRISM-21, PPIS is be calibrated using three Polarimetric Active Radar Calibrators (PARCs) located close to the airport. During each flight, PLIS will be also calibrated using five Passive Radar Calibrators (PRCs) and forest within the study area.