Fine Resolution Radar for Near-Surface Layer Mapping

It is estimated that sea levels have risen 4 to 8 m in the last century. Currently, there is much uncertainty regarding the contribution to this rise from melting ice sheets and glaciers. The key parameter in quantifying the ice sheets contribution is assessing their mass balance. The accumulation rate is a key parameter in computing the mass balance. Remote sensing techniques are required to reduce the uncertainty that currently exists in accumulation rate measurements due to sparse sampling of ice cores and pits. A wideband FM-CW radar was developed to map the near-surface internal layers with high resolution. The radar operated at frequencies from 500 to 2000 MHz. With this bandwidth, the free-space resolution is 10 cm. We used a YIG oscillator in a Phase-Locked Loop configuration to obtain an extremely linear transmit signal. We leveled the power of the transmit signal using an Automatic Gain Control system. The entire radar fits inside one CompactPCI chassis. We analyzed the effect of any amplitude variation and phase non-linearity in the transmit signal on the sideband performance of the IF spectrum. We also developed a simple phase-noise model for a YIG oscillator, and compared our model with the actual phase-noise performance of the YIG oscillator. We tested the radar extensively in the laboratory and field. We obtained excellent internal layer mapping from the 2003 field experiment in NGRIP camp, Greenland and from the 2004 field experiment in Summit camp, Greenland. We are able to see internal layers to a depth of 200 m with fine resolution.