POLARIS: ESA´s airborne ice sounding radar front-end design, performance assessment and first results

This paper addresses the design, implementation and experimental performance assessment of the RF front-end of an airborne P-band ice sounding radar. The ice sounder design comprises commercial-of-the-shelf modules and newly purpose-built components at a centre frequency of 435 MHz with 20% relative bandwidth. The transmitter uses two amplifiers combined in parallel to generate more than >128 W peak power, with system >60% PAE and 47 dB in-band to out-of-band signal ratio. The four channel receiver features digitally controlled variable gain to achieve more than 100 dB dynamic range, 2.4 dB noise figure, 160 ns receiver recovery time and -46 dBc 3^rd order IMD products. The system comprises also, a digital front-end, a digital signal generator, a microstrip antenna array and a control unit. All the subsystems were integrated, certified and functionally tested, and in May 2008 a successful proof-of-concept campaign was organized in Greenland. The system detected the bedrock under 3 km of ice, and internal layers were mapped up to 1.3 km.