SAR Scientist Highlights Archive

June 2021

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 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.”

April 2021

Josef Kellndorfer heartily remembers receiving computer hard drives in the mail containing the data he needed for his research in the 1990s.

Those hard drives came from the Alaska Satellite Facility (ASF), traveling the roughly 4,400 miles to Massachusetts, where he worked at the Woods Hole Research Center, now known as the Woodwell Climate Research Center. Today he is a distinguished visiting scientist at the center but maintaining a strong connection to the satellite facility.

Things have changed mightily since those hard-drive days. He now gets the data he needs from the ASF by tapping on his computer keyboard.

He has been an integral player over his years of official and unofficial connection to the ASF Distributed Active Archive Center (DAAC), which is funded by NASA and part of the University of Alaska Fairbanks Geophysical Institute. And it has shown in the sharp increase in the number of researchers acquiring the data. They tap in from around the globe.

Josef is among the people who they can thank for that.

Josef’s interest in radar remote sensing arose from his studies in geography, remote sensing, and computer science at the Ludwig-Maximilian University of Munich. He had enrolled in a class, which had just two other students, taught by Dr. Wolfgang Keydel who was head of the Radar Section at the German Aerospace Research Center DLR.

“And he instilled in me an interest in using radar for remote sensing, which was my other passion back then.”

Josef’s passion for remote sensing was instilled by his grandfather, Heinz Schmidt-Falkenberg, who was head of the Section of Photogrammetry and Remote Sensing at Germany’s Federal Ministry of the Interior’s Institute for Applied Geodesy, today known as the Federal Agency for Cartography and Geodesy.

As part of Germany’s Antarctic Research, his grandfather coordinated an ocean-ice-atmosphere science plan supporting the establishment of ESA’s receiving station for ERS-1 on the Antarctic Peninsula. The work led to his grandfather being awarded the German Medal of Honor.

With his studies in geography completed in Germany, Josef had two high-priority items next on his list: learning to speak English and deepening his knowledge of radar remote sensing. He asked his professor for a recommendation on who to learn under.

The professor suggested Fawwaz Ulaby at the University of Michigan. So with a one-year stipend from the German Academic Exchange Service, Josef headed to the United States.

“I had the great fortune to study and work with Fawwaz and the Michigan team, including many distinguished SAR researchers like Craig Dobson, Kamal Sarabandi, and Leland Pierce. That was 1994,” he said. “So I am now in the 27th year of my one-year visit to the U.S.!”

It was at the University of Michigan where Josef became exposed to the Alaska Satellite Facility, where he and others started to get their first datasets in the 1990s. He remained at the university until 2005, when he left for Woods Hole, leading projects involving remote sensing and GIS applications to map forest degradation and biomass dynamics in various Earth ecosystems.

“My projects got increasingly data-intensive from that first biomass map of the United States (Lower 48) to the pan-tropical mapping of forest with cloud-penetrating SAR data.”

•••

The story of the mailed hard drives is important because it set Josef and others on the quest for easier access to the SAR data stored at ASF.

For Josef, that increased connection to ASF began in the mid-2000s.

"I had a big project funded by several foundations — Google, Moore and Packard foundations — to do a pan-tropical mapping of basically the vegetation in the tropics, which was, back then for us, key to unlock the question of how can we monitor our tropical forests and the whole idea of bringing that into the climate negotiations on the big topic of REDD — Reducing Emissions from Deforestation and forest Degradation,” he said.

He wanted to demonstrate through the project that the tools at the time existed for such heavy data work. Those tools included the ALOS satellite of the Japan Aerospace Exploration Agency.

"But back then the computer power was such that I built my own computer cluster at the Woods Hole Research Center, now called the Woodwell Climate Research Center, and I arranged with colleagues at ASF that they would ship hard drives to me,” he said.

"So I had a shipment of hard drives of these, back then, 17,000 ALOS satellite scenes. And so I started to become a big data user with them, and as part of that I tried to use a working group at some point, and we started to discuss ‘How do we bring these datasets easier to users?’”

Josef served as chair of that group — the ASF User Working Group — in 2013 and 2014.

"And now, of course, 15 years later the picture is completely different. We no longer ship hard drives. It's all in the cloud."

•••

Josef formed his company, Earth’s Big Data, in 2016. His clients include such prominent entities as the World Wildlife Fund, NOAA, and NASA. And he’s quite busy.

"My focus is we need to move forward, particularly when we look at this Sentinel-1 mission that we have from Europe right now, which is a big data holding for the Alaska Satellite Facility, and then, as we move into the next NASA mission, the NISAR satellite mission where we have — where we're thinking about science data volumes of 100 terabytes per day.

"So it all has to be a cloud-based solution, so now, my relationship is very much working with ASF on optimizing data access, and the cloud and streaming solutions of how we identify these big datasets, and so I continue to work in trying to analyze big-scale satellite data.

"And so it continues, and I look forward to many, many more years of that relationship, because, together, I think we can do a really big-scale project. I'm always interested in the global picture as a geographer by training."

January 2021

Dr. Paul Rosen is Project Scientist for the NASA-ISRO SAR (NISAR) mission. NISAR will measure Earth’s changing ecosystems, dynamic land surfaces, and ice masses, providing critical measurements for carbon cycle modeling, natural hazards research, sea level rise, groundwater exploitation, and more. With its all-weather, day/night, multi-frequency, polarimetric capability, NISAR will also support a host of other applications.

Dr. Rosen is applying 35 years of experience in Earth and planetary radar remote sensing to guiding NISAR science and the potential benefits and impact of these data in the science and applications community. This entails interacting with scientists, engineers, managers, and the public, at all levels and in many capacities. He expects NISAR to have a major impact on how science and applications are developed using synthetic aperture radar (SAR) data, noting that NISAR will provide the world with an unprecedented source of data, processing tools, and educational materials. NASA’s Alaska Satellite Facility Distributed Active Archive Center (ASF DAAC) will take a leading role in NISAR data distribution and education.

August 2020

Bernd Scheuchl brings more than 25 years of experience using synthetic aperture radar remote sensing data in both industry and academia to his role as the chair of ASF’s User Working Group. As leader of the advisory board, he helps shape ASF’s role as a NASA Distributed Active Archive Center, ensuring the data are accessible for all users. Scheuchl works to coordinate ASF’s support of the upcoming NASA/ISRO SAR mission (NISAR) through development of new SAR techniques and transformative technology. As a researcher, his team’s work is at the forefront of using SAR data to study Antarctica, including producing its first continent-wide ice velocity map.

February 2020

As Director of ASF, Dr. Nettie La Belle-Hamer’s mission is to support and mentor her team of driven professionals as leaders in remote sensing and data accessibility. She applies her research background in space physics to guide the facility as it provides high-quality data to meet the evolving needs of its users. Dr. La Belle-Hamer has been a part of ASF for 19 years and was appointed Director in 2002. She is also Deputy Director of the Geophysical Institute, where she works to develop and expand the capabilities of both organizations.

October 2019

As ASF Chief Scientist, Franz J. Meyer leverages almost two decades of remote sensing research experience to act as the interface between ASF and the scientific community.

Meyer has spent his career working with space agencies around the world to develop processing techniques and methods for synthetic aperture radar, or SAR, data. These techniques have been used to explore signals related to surface deformation such as earthquakes and volcanic eruptions. Recently, his research has expanded into the development of remote sensing-based hazard monitoring. He has led trainings around the world to help governments and organizations increase their capacity for radar techniques and hopes to transform SAR into a tool to meaningfully influence people’s lives on a daily basis.

SAR Scientist Highlights Archive