A Technique to Track Earth’s Subtle Movements with Orbiting Radars is Heating Up

About every six days, ghostly images of most areas on earth emerged from the European space agencies. Sentinel-1 program the technology capturing these images, synthetic aperture radar also known as SAR is booming in the coming years. It may reveal tiny changes on every patch of earth. Daily optical imagery, satellites like the US geological surveys Landsat use reflected light to passively take photos from high in the sky.

Sentinel-1 takes its snapshots actively by using radars, unlike optical technology, which produces the best images on sunny days, SAR, penetrates clouds and works at night and intend to onboard the satellite emits microwave pulses to the surface of the earth and records. The echos that bounce back. The more signals that gather the higher, the resolution of the image, the synthetic aperture of SAR satellites describes an important advance instead of building an extremely large antenna to capture returning waves.

These satellites combine signals from a relatively small antenna, moving through space to sharpen resolution by comparing measurements from different positions, SAR data can reveal. Topography images are often colorized to highlight important features such as flooded regions.

                          

What started as a tool for military surveillance is now essential to earth scientists. Examining changes in the landscape over time. Comparing SAR images from the same vantage point at different times can reveal surface movements from meters to millimeters. This technique is known as interferometric SAR, or InSAR one of the first applications that emerged in 1989. When researchers observed the subtle swelling of fields in California's Imperial Valley after crops were irrigated in 1993, 

a groundbreaking study used InSAR to reveal how the ground shifted after a powerful earthquake rippled through Landers California colors on the map show meters of movement concentrated along the faults. The technique also revealed changes in the land miles away from the epicenter of the earthquake.

Two years later, glaciologists used InSAR to measure the flow of ice streams in Greenland, which accelerated as the planet warmed more recently, geophysicists were able to detect signs of deformation at several volcanoes in the East African rift zone. Some of which were thought to be inactive. The Corvette, the volcano near the city of a WASA has been inflating by almost seven centimeters a year. The launch of the twin Sentinel-1 satellites in 2014 and 2016 provided researchers with regular freely available data.

Norway, Sentinel-1 data to create a deformation map of the entire country in order to identify rockslide hazards inadvertently, they discovered that parts of the train station in Oslo were sinking. Private companies are also investing in SAR technology, ISI, a finished space startup Lance to launch eight or more satellites in 2021, adding to its growing fleet already in orbit. Ultimately they hope to capture snapshots of most places on earth several times per day and produce images with 50 centimeter or higher resolution researchers envision close to real-time SAR observations to change the way we live. It could provide crucial information on natural disasters, such as floods, quickly identifying the most inundated areas can guide response efforts. 

References:

Gabriel, A. K., et al. (1989). "Mapping small elevation changes over large areas: Differential radar interferometry."  94(B7): 9183-9191.      

Joughin, I. R., et al. (1995). "Observations of ice‐sheet motion in Greenland using satellite radar interferometry."  22(5): 571-574.

Massonnet, D., et al. (1993). "The displacement field of the Landers earthquake mapped by radar interferometry."  364(6433): 138-142.

Wu, K., et al. (2020). "Simulation Study of Moon-Based InSAR Observation for Solid Earth Tides."  12(1): 123.

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