USGS

Venus Mapping White Paper

Open-File Report 95-519


I. Introduction

This report is a guide to possible uses for Magellan data within the context of Venus mapping. The goal is to provide a set of "cookbook" approaches which may allow mappers working over a broad range of viewing geometries to clearly communicate the surface properties of their units to a wide audience, with due care given to the ambiguities which can enter into such techniques. Backscatter coefficients and ancillary data (emissivity, topography, rms slope, and reflectivity) for Venus obtained by Magellan provide a unique view of the surface roughness at a variety of scales and the dielectric properties of the terrain. The active illumination and control of incidence angles afforded by the radar instrument also create a dataset having quantitative properties that can be compared with observations of potential terrestrial analog surfaces. In preparing a Venus map, it is thus valuable to the mapper and the reader to provide a distillation and interpretation of the quantitative properties of geologic units from the measurements available.

A set of presentation methods are shown, some of which are offered as standards for the use of quantitative data in map texts and figures. Many of the topics covered here are introduced in The Venus Geologic Mappers' Handbook [Tanaka et al., 1994] and this paper expands on these issues with information gained during analysis of Magellan data. One of the primary motivations of this paper is to archive equations and tables needed for Magellan data processing and to provide rationales for the importance of each dataset to future mappers and map users.