Radar sounders for Earth and the Planets

Orbiting radar instruments provide a unique means for measuring, on a large scale, the thickness of ice-sheets on Earth and the planets. Studies undertaken within the context of ESA's ACRAS project have identified a num-ber of candidate instruments capable of providing the data needed to determine the distance between ice-sheet surfaces, internal layers, bedrock, and sub-ice sheet water surfaces. This paper reviews the requirements that drive missions associated with Terrestrial sounders and sounders for various planetary destinations. The paper then identifies candidate instrument configurations for the various missions and predicts their performance and indicative budgets.