Long before Robert Herrick was a research associate professor at the Geophysical Institute, he was a doctoral candidate at Southern Methodist University in Dallas, Texas working on the Magellan mission. Launched by the National Aeronautics and Space Administration in 1989, the imaging radar orbited Venus until 1994. Herrick’s current research has brought him full circle. Along with colleagues, Herrick has reprocessed the data collected by Magellan. The results have been clarifying.
Previously, the topography of Venus was charted using radar altimetry. Lacking a clear line of sight through thick yellow clouds, scientists tracked the travel time of radar waves bouncing between the surface and the satellite to model basic geologic formations. Stereo radar images were also collected during the Magellan mission. Herrick uses the analogy of a View-Master to describe the way in which satellite images of two separate perspectives are combined to achieve stereo-vision, or a three dimensional effect.
Herrick and his team have reprocessed those stereo radar images to produce a higher-resolution map of Venus’ topography. Though the computations for topography require only simple trigonometry, it is sophisticated image matching techniques and contemporary computer resources that make reprocessing the Magellan data possible. With the improved topography, many of the complex tectonic features on Venus can now be studied in detail.
Renewed interest in the morning star has been a long time coming. After several Mars-focused missions, scientists have identified an obvious lack of high-resolution data available for Venus.
“For most of the last 15 years the emphasis for NASA’s unmanned program was doing things related to the search for life. If your focus is on the search for life, Venus is not very useful. The surface temperature is about 900 degrees [Fahrenheit],” Herrick said.
But it is that harsh environment that has again piqued research interest. As more planets are discovered orbiting distant stars, comparing the similarities and differences between Venus and Earth has allured researchers, Herrick said. Despite similar size and distance from the sun, the two planets have dramatically dissimilar atmospheres. Understanding why the stark contrasts exist is key to evaluating the likelihood that an Earth-sized planet will be an Earth-like planet.
Steady advancements in remote sensing have driven down costs of radar technology, which makes studying Venus much more accessible. Making up for the absence of high-resolution topography and imaging of Venus is now an affordable and desirable enterprise.