Design of a Forward Looking Synthetic Aperture Radar for an Autonomous Cryobot for Subsurface Exploration of Europa and Enceladus

The project consists of (1) design of an array of four conformal cavity-backed log-periodic folded slot dipole array (LPFSA) antennas that form the radiating elements, (2) design of a radar system that includes RF signal generation, 4x4 transmit-receive antenna switching and isolation and digital SAR data processing and (3) field testing of the SAR system. The antennas were designed, fabricated, and lab tested at the Center for Environmental Technology (CET) at CU-Boulder. The radar analog and digital system were also designed and integrated at CET utilizing rugged RF components and FPGA based digital waveform generation. Field testing was performed in conjunction with VALKYRIE tests by Stone Aerospace in June, 2015 on Matanuska Glacier, Alaska.

In this presentation we will describe in detail the following aspects pertaining to the design, analysis and testing of the endfire SAR system; (1) waveform generation capability of the radar as well as transmit and receive channel calibration, (2) theoretical analysis of the radial resolution improvement made possible by using the radar in an endfire SAR mode along with the free space radar tests performed to validate the proposed endfire SAR system, (3) a method for azimuth ambiguity resolution by operating the endfire SAR in a bistatic mode,(4) modal analysis of the layered cylindrical LPFSA antenna structure and a forward model of the wave propagation path through planar layered ice medium and (5) analysis and interpretation of the in-situ measurements of the antennas and endfire SAR operation on the Matanuska glacier.