The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor is one of five sensors on board NASA’s Terra satellite. ASTER data and imagery are crucial tools for monitoring volcanoes for any clues of imminent eruptions, for studying volcanoes during an eruption, and for analyzing impacts after an eruption. Scientists use ASTER data to study the composition and temperature of gasses emitted by a volcano, to look for changes to surface temperatures, as well as interpret topographic data. In visible and near infrared ASTER imagery, vegetation is red, snow, clouds and smoke are white, and lava flows are shades of gray, with newest flows being black. In visible and near infrared imagery, volcanic plumes are white to gray, and may look similar to other smoke or clouds… …so ASTER Thermal Infrared imagery is more often used when analyzing volcanic plumes. In thermal infrared images, the Sulfur dioxide gas in a volcanic plume appears as a slightly blue-ish color. To study surface temperature changes, scientists use thermal infrared imagery. ASTER’s thermal infrared telescope can detect surface temperatures of up to 100-degrees Celsius (212 degrees Fahrenheit). In this thermal infrared image, newer, hotter lava are brighter white areas; cooler or older lava is gray-to-black. Black spots are clouds. Volcanic gasses appear blue-ish. If increased thermal output has been detected at a volcano, ASTER may be tasked to collect data at that location. Many images of active volcanoes are obscured with clouds or volcanic plumes; however, as the Terra satellite revisits a site at least every 16 days, … …there is an increased probability that a clear image will be captured. Volcanologists use these time-series of clear images to study changes to volcanoes over time. ASTER also collects stereographic data, which are used to derive topographic information and can help predict possible lava flow routes. Images captured before and after an eruption event are used for post-eruption flow volume calculations. ASTER topographic information is used when creating a hazard map and planning countermeasures against any possible disasters from future eruptions. For more information on how to access ASTER data please visit the LP DAAC’s data access web page.