Radar's eye that not even clouds can block

Seattle and Portland, Oregon, an area famous for having the cloudiest weather in the United States, were clearly captured from space. The Earth observation satellite 'NISAR (NASA-ISRO Synthetic Aperture Radar)' jointly developed by the National Aeronautics and Space Administration (NASA) and the Indian Space Research Organization (ISRO) succeeded in capturing detailed images of the Pacific Northwest using cloud-penetrating synthetic aperture radar (SAR) technology.

NISAR, launched from India's Satish Dhawan Space Center in July 2025, is equipped with a large antenna reflector with a diameter of approximately 12 meters. The L-band radar used by this satellite has a wavelength of up to 24 centimeters, so it can detect even minute changes in the earth's surface while passing through clouds.

Why is this technology important?

NISAR's radar imagery allows comparative analysis over time to identify subtle changes in forests, wetlands, urban areas, and infrastructure. In particular, it is possible to detect subtle tectonic movements related to volcanic activity, glacier movement, fault slip, and slow-moving landslides.

“The Pacific Northwest is home to millions of people and supports major industries including technology, aerospace, agriculture, and forestry,” said Brandy Downs, a remote sensing engineer at NASA’s Jet Propulsion Laboratory (JPL). “This video shows how NISAR data can contribute to resource management, natural disaster monitoring, and environmental decision-making.”

What the radar image shows

This video, filmed on November 10, 2025, includes waterways, road networks, and cityscapes around Portland and Seattle. Radar images do not show actual colors like regular photos. Instead, the color is determined by a combination of the strength and polarization of the radar signal.

The area shown in magenta in the image is where radar signals are strongly reflected from flat surfaces such as roads and buildings. The yellow dots are analyzed to be influenced by various factors such as land cover, soil moisture, and surface shape. Yellow-green represents the forests and wetlands that cover the area, while the summits of Mount Rainier and Mount St. Helens are depicted in dark blue. This refers to a relatively smooth surface, such as water or an exposed mountain peak.

In particular, purple square patterns with precise right angles were discovered among the light green vegetation at the foot of each mountain. This was created artificially and is presumed to be traces of forest thinning or vegetation that has grown back after past thinning.

The power of observing the 12-day cycle

“A single radar image is just a snapshot of surface conditions,” Downs said. “Scientists typically rely on time series images to figure out what’s going on.” NISAR produces continuous radar measurements by observing the same area twice every 12 days, which can tell the full story of land surface changes.

This time series analysis allows scientists to pinpoint where trees and plants have been removed, regrow, or destroyed and estimate the amount of carbon stored in forests. Additionally, by monitoring the boundaries of water and wetlands, insight into flood risk or changes in river channels can be gained.

NISAR is managed by the California Institute of Technology (Caltech), and JPL led the U.S. project and provided the satellite's L-band SAR and antenna.