NASA's C-20A (Gulfstream III) Earth science aircraft, carrying a specially designed synthetic aperture radar, recently completed the latest in a series of data collection flights over Colorado's centuries-old Slumgullion landslide. The goal of the research flights, funded by NASA's Science Mission Directorate, is to aid scientists' understanding of the mechanisms controlling landslide motion.
Scientists have identified seasonal variations in the movement of the Slumgullion slide, located in the San Juan Mountains of southwestern Colorado. The landslide moves at a rate of about 7 meters, or 23 feet, per year. The entire slide is 6.8 kilometers, or 4.2 miles, long. First studied in the late 1800s, scientists believe that the original slide occurred more than 1,000 years ago.
Developed by NASA's Jet Propulsion Laboratory, the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) mounted on the aircraft's underbelly uses a technique called interferometry to detect and measure very subtle deformations in Earth's surface.
"The combination of the four UAVSAR flight lines over the Slumgullion landslide will allow us to extract a detailed 3-D map of the motion within the landslide that has not been possible before," said Eric Fielding, JPL principal investigator for this study.
"We will compare the UAVSAR measurements with satellite InSAR (interferometric synthetic aperture radar) measurements made in the field by colleagues at the U.S. Geological Survey and the University of California at Berkeley to understand how the slide is responding to variations in snowmelt and rainfall and other sources."
The data collection process is aided by a NASA Dryden-developed Precision Platform Autopilot in the aircraft that enables it to repeat flight patterns over a previous flight track within 10 meters of the original while flying at altitudes up to 41,000 feet.
The Slumgullion landside study benefits from the use of an airborne platform as the flight paths can optimize the study of the landslide motion. The high resolution and L-band wavelength of the UAVSAR allow scientists to make measurements of the surface deformation over periods from days to a few months.
Fielding explained that active slope movement appears to occur in three annual seasonal phases, including the slow season when little moisture occurs to cause movement, an acceleration phase when snowmelt provides movement and a deceleration phase when the previous activity decreases.
The NASA aircraft carrying the UAVSAR first flew over the area in August 2011 and established baseline surface measurements during the "slow" season. Flight lines were repeated in April 2012 to measure the activity of the acceleration phase. Two sensor flights were flown in May 2012 during the deceleration phase, with the final slow-phase flights taking place in late July.
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