Validation of AMSR Snow Depth on Sea Ice Retrievals Using an Airborne Pulse Radar: Final Report

This is the final report on the project entitled “Validation of AMSR snow depth on sea ice retrievals using an airborne pulse radar.” This is a collaborative project between the Center for Remote Sensing of Ice sheets (CReSIS) at the University of Kansas and NASA Goddard Space Flight Center (GSFC). We designed and developed ultrawideband radars for measuring thickness of snow over sea ice from the surface and from aircraft. We successfully used the radar designed for surface-based measurements to collect data over snow-covered sea ice in Antarctica. Radar-derived snow thickness estimates were in excellent agreement with physical measurements of snow thickness. We obtained a correlation coefficient of 0.95 between the radar estimates and in-situ measurements, and a vertical resolution of about 3 cm. We modified the radar for operation on a fast-moving aircraft. The experimental results were useful to demonstrate the concept of using an ultra-wideband radar to measure snow thickness from an aircraft. However, we could not collect data over many flight lines to support AMSR validation activities. This is mainly because we had to reduce sweep rate for minimizing nonlinearities in the transmit waveform. We tested the radar performance using a short delay line in the laboratory, which did not reveal transmitter waveform non-linearities that affected its performance at typical aircraft operating altitudes. We redesigned and rebuilt the radar with a fast-settling Phase-Locked Loop (PLL) and evaluated its performance using a long delay line in the laboratory. The laboratory test results show that the radar can be operated at sweep rates greater than 4 kHz with a vertical resolution of about 5 cm.