Data from satellite radar instruments have become a valuable tool for detecting sudden land changes caused by earthquakes, volcanic eruptions, and landslides, and for monitoring slower movements driven by the loss of groundwater, land subsidence, or the motion of tectonic plates. Further, the field of interferometric synthetic aperture radar (InSAR) has seen tremendous development in the past two decades as it enables users to map small movements of Earth’s surface at larger scales than ever before.
Atmosphere conditions can mask or mimic land surface motion, as clouds ever so slightly slow down/delay the radar signal. For example, if there were a cloud over a volcano on the first take (see the diagram above) and the skies were cloud free on the second take, then it may seem that the volcano might be inflating because the radar signal returned to the satellite faster, suggesting uplift. Such artifacts in the radar imagery caused by the atmospheric conditions need to be accounted for in the data analysis.
The TROPO dataset is important because it provides atmospheric corrections that can be used with any radar satellite. These corrections increase the accuracy of the radar measurements for many processes that cause Earth’s land and ice surfaces to move and deform.
“This tropospheric correction dataset is designed to support current and future radar missions — including the NISAR mission that launched in July — by effectively correcting the path that pulses from satellite radar instruments travel,” said Marin Govorcin, Research Scientist at NASA Jet Propulsion Laboratory (JPL). “This improves the clarity and accuracy of surface deformation measurements and brings us closer to understanding the processes driving change beneath the surface.”
The TROPO product uses high-resolution data from the European Centre for Medium-Range Weather Forecasts (ECMWF) HRES weather model as inputs to compute multi-layer tropospheric corrections, which account for both hydrostatic and wet atmospheric delays from the surface to the top of the troposphere. These corrections can then be applied to radar acquisitions from several platforms, including the NASA/Indian Space Research Organization SAR (NISAR) satellite mission, the European Space Agency’s Sentinel-1 mission, and the Japan Aerospace Exploration Agency’s Advanced Land Observing Satellite (ALOS) mission, as well as for airborne instruments such as the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR).
By reducing tropopsheric noise in satellite radar observations, the TROPO data product enhances scientists’ ability to detect both sudden and gradual land changes with greater confidence. Taking it a step further, OPERA routinely produces atmospheric correction data from the ECMWF model on a daily basis, every six hours, which users can then incorporate directly into their InSAR processing workflows.
“By making the TROPO products routinely available, we’re making it easier for researchers to perform tropospheric corrections and use the best available data,” said OPERA Project Manager Dr. David Bekaert. “Since they’re radar mission-agnostic, these products can support the entire satellite radar community.”
Data Access
All OPERA products are accessible through the NASA Earthdata Search portal. The OPERA JPL website has links to all available OPERA products as well.
