Maybe most of the inflation occurs right after the eruption, and the rate slows down as it gets closer to the next eruption . The research was led by geophysicist Zhong Lu of Raytheon STX Corp., a USGS contractor at a satellite data center in Sioux Falls, South Dakota. Lu and Wicks studied Westdahl with five other researchers from the USGS, the Alaska Volcano Observatory and the Cascades Volcano Observatory. Using satellite radar to measure inflation of volcanoes has been tried only on Westdahl and on Alaska s Okmok volcano, so its value for predicting eruptions remains uncertain. Using radar to measure uplift or sinking is difficult.
Scientists compare radar images of the same area over periods of months to years.
Each fringe represents a certain amount of vertical movement. The ERS satellites, launched in 1991 and 1995, were not designed to measure volcanoes and land sinking. Their main mission is to study oceans, atmospheric conditions, ice caps and coastal regions. Sites include Cambodia s Angkor Wat Temple, French Polynesia, Papua New Guinea, the Philippines and Australia's coastal wetlands. The airborne radar, which is used to demonstrate technology for spaceborne radar missions , will not only collect geological data, but information for coastal analysis, oceanography, forestry, hydrology and archaeology.