A model for altimeter returns from penetrable geophysical media

The radar altimeter is a well-understood instrument for monitoring the world's oceans. There has been a recent effort to extend altimeter techniques to the study of the world's ice sheets. To this end, several authors have developed average altimeter waveform models that incorporate pulse-penetration effects to varying degrees. In this paper, the authors extend these models to more adequately account for the effects of surface roughness and subsurface inhomogeneities on the average scattered waveform. This leads to a waveform model that is useful in analyzing altimeter returns obtained over a wider range of geophysical media, such as snow, ice, and foliage, which are characterized by strong subsurface inhomogeneities. Representative results of applying this extended model to airborne altimeter measurements made over various regions of the Greenland ice sheet in September 1991 are provided.