An improved coherent radar depth sounder

The University of Kansas developed a coherent radar depth sounder during th e 1980s. This system was originally developed for glacial ice-thickness mea surements in the Antarctic. During the field tests in the Antarctic and Gre enland, we found the system performance to be less than optimum. The field tests in Greenland were performed in 1993, as a part of the NASA Program fo r Arctic Climate Assessment (PARCA). We redesigned and rebuilt this system to improve the performance. The radar uses pulse compression and coherent signal processing to obtain h igh sensitivity and fine along-track resolution. It operates at a center fr equency of 150 MHz with a radio frequency bandwidth of about 17 MHz, which gives a range resolution of about 5 m in ice. We have been operating it fro m a NASA P-3 aircraft for collecting ice-thickness data in conjunction with laser surface-elevation measurements over the Greenland ice sheet during t he last 4 years. We have demonstrated that this radar can measure the thick ness of more than 3 km of cold ice and can obtain ice-thickness information over outlet glaciers and ice margins. In this paper we provide a brief survey of radar sounding of glacial ice, f ollowed by a description of the system and subsystem design and performance . We also show sample results from the field experiments over the Greenland ice sheet and its outlet glaciers.