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.

Bowman_cropped

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.

On Demand Sentinel-1 GAMMA InSAR and RTC Products Now Available in Vertex

The Copernicus GLO-30 DEM is the default option for Vertex On Demand products

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

FRINGE 2021 Advances in the Science and Applications of SAR Interferometry and Sentinel-1 InSAR
NEW! Vertex: On-Demand Processing video tutorial

Sentinel-1 GAMMA RTC and GAMMA InSAR

NEW! Vertex: Downloading Data video tutorial

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 Data How-To

Data Recipes To Make Using SAR Data Easier

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.

Howard Zebker....continued

Howard was born in the Southern California city of Ventura — “You know, it was nice growing up in a beach town” — and has moved a few times back and forth between the San Francisco Bay Area to the north and Pasadena, the home of JPL.

Today, more than 40 years removed from magnetic tape and notebooks, Howard is a professor of geophysics and electrical engineering at Stanford University in California, where he has been teaching since 1995.

He is also head of the university’s Remote Sensing Group, where the emphasis is on interferometric synthetic aperture radar, or InSAR, which can measure changes on the Earth’s surface down to 1 centimeter from satellites orbiting more than 500 miles above the planet.

Howard is actually an InSAR pioneer.

“I started working on aspects of InSAR in the late ’70s, but mainly that work got started in a bigger way in the mid-’80s when I was at JPL,” he said. “We wrote a number of the initial papers on the method.”

Those papers included the groundbreaking 1986 article, “Topographic Mapping From Interferometric Synthetic Aperture Radar Observations,” which was based on NASA-funded research by Howard and Richard Goldstein while the pair worked at JPL. In that paper, published in the Journal of Geophysical Research, the two introduced the world to a new technique that would produce topographic maps far superior to those created through that era’s technology of using stereo pairs of radar imagery.

“We feel that the interferometric technique is a new and useful approach to the remote determination of topographic data,” the two authors concluded in their 1986 paper.

That proved to be an understatement.

Laurence Smith of the Department of Geography at the University of California, Los Angeles wrote in a 2002 review article in the Annals of the Association of American Geographers that “The past decade has seen interferometric synthetic aperture radar progress from a pioneering technology to an accepted remote-sensing tool with diverse applications in the Earth sciences.”

Smith added in that 2002 article that the previous decade “has seen significant improvements in our understanding of earthquakes, volcanoes, and glaciers as a direct result of this technology” and that it “has the potential to provide fundamentally new types of observations.”

InSAR stands out as a significant piece of work in Howard’s lengthy career.

•••

Howard’s resume, as you might gather about someone affiliated with satellites and remote sensing for so long, is robust. His appointments, honors, board and review panel memberships, and speaking engagements are many.

Consider these few — very few — items outside of his numerous roles at Stanford:

• Distinguished Visiting Scientist, NASA Jet Propulsion Laboratory (2019 - 2020)
• Certificate of Recognition for development of Differential Radar Interferometry, June, NASA (2007)
• NASA Technical Review Committee, HICP planetary missions (2004)
• Group Achievement Award, Airborne Imaging Radar System Team, NASA (1990)
• Director's Research Achievement Award, Jet Propulsion Laboratory (1988)
• Best paper award, IEEE Geoscience and Remote Sensing Society (1988)
• NASA Certificates of Achievement: New Technology: Approaches to Modeling Polarization Characteristics of Surfaces for Radar Polarimetry,” NASA (1988-1995)
• Group Achievement Award, Shuttle Imaging Radar (SIR-A) Development Team, NASA (1982)

He is a fellow of the American Geophysical Union, the Institute of Electrical and Electronics Engineers and the Electromagnetics Academy. He has served on numerous National Academy panels, including the Space Studies Board and the Naval Studies Board Advanced Radar Technology Panel.

•••

The Alaska Satellite Facility has been a constant through much of Howard’s professional life, whether as a member of the Alaska Satellite Facility Users Working Group, of which he has been a member since 1998; as a tool for his own research, or as a means through which the next generation of remote-sensing scientists conduct their research.

“All of our students, from the very first year they're here, they start downloading data from the satellite facility, and they run them through our codes here,” Howard said. “So we all rely on ASF for the source of all of our working data.”

“It trains students to go out and be independent scientists working in this field,” he said. “And this is their primary resource for access to data, which is, for any kind of experimental research, where it all starts.”

Click here to continue the story...

Read about other SAR scientists that have been featured in the past.