In this UAVSAR Pauli decomposition, the Holitna River runs through the center of the image. The river is located in southwest Alaska and is the largest river system in the Kuskokwim River basin. The Hoholitna River, seen at the top of the image, is a major tributary and joins the Holitna 20 miles (32 km) from the Kuskokwim River. Both rivers flow through a vast wilderness area and the flat landscape accounts for the extreme serpentine nature of the rivers and the formation of oxbow lakes – U-shaped lakes that form when a meander of a river is cut-off. Many of these lakes are visible is this image. Credit: NASA/JPL 2018
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This multi-temporal RGB composite uses three images of the Mekong Delta acquired at different times during the last year to create a wonderful array of colors. Colorful pixels represent temporal variation while white to black pixels have not experienced any significant change. The diversity of color highlights the region's mix of crop types and the diversity of rice cultivation methods. Because of the ability of SAR to image during the rainy season, this technique is a useful tool for mapping and classifying crop type and rice production methods year round. Credit: Copernicus Sentinel data 2019, processed by ESA; courtesy Rowan Biessel, ASF
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Visible in this false color ALOS PALSAR mosaic image, the Tanezrouft Basin in the Sahara Desert is one of the most desolate locations on Earth, and is known as the “land of terror” from its lack of water and vegetation. Salt flats and sandstone outcroppings create various patterns only visible from high above the landscape. The data were acquired in ‘dual polarization’, from which the artificial color composite was generated. © JAXA/METI 2007; Credit: Jeff Hickey, ASF
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This 1978 Seasat image of Central Pennsylvania's Susquehanna Lowlands was taken by the first civilian SAR mission. Different signal returns from the ridges and valleys reveal their formation through ancient tectonic compression. Pressure from the southeast buckled the rocks into long ridges. Erosion of softer rocks formed valleys, while harder rocks remained in the ridges. Bright spots along the river represent buildings in towns.
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In this ALOS AVNIR-2 image, the interaction of wind and local topography are seen to produce a scouring of rocky hills in southwestern Namibia. This sand-free region, with its own local albedo, stands as a beautiful anomaly in the 1,000-mile-long Namib Desert.
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ASF Celebrates 30 Years of Operations

For 30 years, ASF has provided consistent, high-quality access to Earth observation data acquired from space and from air. From a single antenna taking its first satellite downlink in 1991, ASF has grown into a multi-antenna NASA satellite ground support facility and a NASA Distributed Active Archive Center with over 13PB of Earth observation data available to download.

Check out this VIDEO to learn about who we are and what we do.


Dr. Steve Bowman is profiled on the NASA Earthdata website

Dr. Bowman is the Geologic Hazards Program Manager with the Utah Geological Survey and member of the ASF DAAC User Working Group. Find out how he uses SAR for geologic emergency response, and researching and mapping geologic hazards.

Training and Resources

Synthetic Aperture Radar: Hazards

This six-week edX course teaches the fundamentals of the use of Synthetic Aperture Radar (SAR) remote sensing for disaster monitoring. The course is FREE, with the option to pursue a Verified Certificate. Next class September 7. Information online

NEW! Vertex: On-Demand Processing video tutorial

Sentinel-1 GAMMA RTC and GAMMA InSAR

Earthdata Webinar: Part 1

A basic introduction to SAR data collection, the datasets that are available from the ASF DAAC, and the processing required to extract useful information from the data.

Earthdata Webinar: Part 2

Focuses on Sentinel-1 datasets, discussing options for generating Radiometric Terrain Corrected (RTC) datasets, and present workflows using both ArcGIS and QGIS software.

SAR Image Gallery

SAR Scientist Highlight


JUL 2021 -- Rod Boyce

Howard Zebker, PhD

If you want an idea of how long Howard Zebker has been immersed professionally with satellites and satellite data, just look up the launch date of NASA’s Seasat mission.

June 28, 1978.

Seasat was one of the first Earth-observing satellites and was designed to provide data about the planet’s oceans. It was the first time that NASA sent a synthetic aperture radar into orbit.

Seasat didn’t last long, at just 105 days due to a catastrophic onboard short circuit, but its SAR system and other instrumentation provided more ocean data than had been gathered in the previous 100 years of shipboard investigations.

And it proved the value of space-borne SAR.

Howard was deeply involved in Seasat, working on algorithms for the processors that would handle Seasat’s data and helping design the optical correlator system that would make images from the data that had been downloaded from Seasat onto magnetic tape.

Yes, magnetic tape. Also, there were notebooks — of the paper sort, not of the electronic variety — that people were still using.

“I built the ground support equipment for the radar, which included moving all of the test measurements from being done by hand and written into a notebook to a computer-controlled system that could operate the test equipment and record the results,” he wrote in one email exchange for this recollection of his work and his connection to the Alaska SAR Facility, which would later become the Alaska Satellite Facility at the University of Alaska Fairbanks.

“This seems obvious and is the way things are done today, but 40-plus years ago this was one of the first times this was attempted,” he wrote.

Seasat was Howard’s first project at JPL, and it got him connected with the Alaska facility, which was one of five northern hemisphere ground stations receiving Seasat data.

“So I have used data from ASF off and on for decades,” he said. “I have been on the User Working Group and continue to rely on ASF as a source of data and other computing resources and a way to interact with the community. And that continues today.”

So you see, Howard has been around a while.