By Paul E. Racette, DSc
Dr. Alberto Moreira, president of the IEEE Geosciences and Remote Sensing Society, has a dynamic vision for remote sensing that is now, he says, in its golden age. And he sees that the rewards of maturity also bring responsibility. “This is a living Earth. We have a responsibility to leave the Earth at least in as good of condition as it is today.”
Dr. Moreira is a pioneer in research and development of high-resolution radar signal processing, innovative synthetic aperture radar (SAR) system concepts and associated techniques like radar tomography, digital beam forming and advanced imaging modes. He received the B.S.E.E. and the M.S.E.E. degrees, in 1984 and 1986, respectively, from the Aeronautical Technological Institute ITA, Brazil and the Eng. Dr. degree (Honors) from the Technical University of Munich, Germany, 1993. In 2003, he received a full professorship from the University of Karlsruhe, Germany, in the field of Microwave Remote Sensing. As its chief scientist and engineer, Prof. Moreira managed from 1996 to 2001 the SAR Technology Department of the Microwaves and Radar Institute at the German Aerospace Center (DLR). Since 2001, he is the director of the Microwaves and Radar Institute at DLR. The Institute contributes to several scientific programs and space projects for actual and future air- and space-borne SAR missions. Prof. Moreira is the Principal Investigator for the TanDEM-X mission led by DLR.
His personal interests are dynamic, too. He is South American from Sao Jose dos Campos in Sao Paulo, Brazil. He went to Germany for his PhD and met his wife, also a Brazilian, in an art museum, an interest they share. His father is an architect, plays the violin and paints and his mother is a professional musician, from whom he learned to play the piano. He and his wife have two children, 12 and 14. His hobby, begun when he was 17, is gliding a tow airplane without a motor in which he has participated in world championships. “It’s incredible the flight of gliders, a very nice experience. And this perhaps inspired me to work with space research. When you fly you are like a bird and can see the ground below, just like remote sensing.”
Paul Racette, Earthzine Editor in Chief, interviewed Alberto Moreira at the 2010 IGARSS in Honolulu.
Earthzine: How did you enter the field of remote sensing?
Alberto Moreira: My professor in Brazil told me if I wanted to make good research in my field I should go to either the United States, Europe, or somewhere else. I got a scholarship from the German government and with that I came to DLR, the German Aerospace Center, in ’86, to earn a PhD in synthetic aperture radar. And this was a very challenging time for SAR because at that time, a few people had a deep understanding onhow it works. Even the digital processing algorithms that could deliver a very focused image were not well understood. And my task at DLR was to develop a real-time algorithm for our airborne SAR. At that time we had workstations that were very slow. It took two days to process one SAR image, with some ten by ten kilometers. They had a request to have these in real-time. That was the topic of my PhD to develop an algorithm for real-time airborne SAR processing. At the end of my PhD, this was implemented in the airborne SAR. We had twenty-eight digital signal processors, dedicated computational units. We could have SAR images in real-time with three meters resolution, and these were used for more than ten years during innumerous airborne campaigns.
Earthzine: You’re now the director of the Microwaves and Radar Institute.
Alberto Moreira: This does not happen very often at DLR. I made a sort of career at DLR at the start as a PhD student. I was contracted as a researcher and then, after three years, I was a group leader responsible for ten people. In ’96, I got the responsibility of a full department with some 35 people. Then in 2001, I was very proud to be selected as the director of the microwaves and radar institute. We are some 130 people. Our institute is shaping the future radar missions of the German space program. All the new radar missions in Germany are coming from our institute.
Earthzine: Does that include the ESA, the ERS-1?
Alberto Moreira: We have made substantial contributions in the conceptual analysis, the performance estimation and calibration for all the ESA radar missions. For the Sentinel-1 we have a contract from industry for defining the calibration algorithms of the mission. We have also had international programs with NASA. Since the eighties we have been collaborating with JPL in the scope of the Shuttle Imaging Radar missions SIR-C/X-SAR, and also SRTM. DLR has contributed with the X-band radar systems for these missions. SIR-C/X-SAR in ’94 was a milestone in radar development because this was the first mission with three radars at three different frequencies. In 2000, with the SRTM [Shuttle Radar Topography Mission] we had one radar from JPL, a C-band radar, and the X-band radar from Germany, both for topographic mapping. That mission was also again a milestone in remote sensing because the topographic data from interferometric SAR measurements became a reference for the geocoding of remote sensing data for geoscience applications.
Earthzine: The TerraSAR-X is Germany’s first radar satellite.
Alberto Moreira: That’s a mission in a public-private partnership between DLR and the German industry. TerraSAR-X was launched in June 2007. Since then it is supplying high-resolution radar images for scientific and commercial applications. TerraSAR-X is the fruit of consistent development of German radar technology over many years and is an example of successful cooperation with the German space industry. Our institute is responsible for the system engineering, radar instrument operation and calibration and is involved in a number of scientific proposals for data evaluation.
Earthzine: How many free flying SARs have been launched?
Alberto Moreira: We have a tremendous development in the radar area. Ten years ago, we had two satellites: RadarSat-1 was one and the ERS-2. These were single frequency, no polarization and so on. As of today we have fifteen spaceborne radars flying with different frequencies and polarizations and this has been a huge development. The great number of SARs in space is a prominent example of the golden age of remote sensing.
Earthzine: Fifteen SARs?
Alberto Moreira: All SARs! In addition to ERS-2 and Radarsat-1, that are still operating, we have three CosmoSkymed satellites, we have the ENVISAT/ASAR satellite, we have ALOS/PALSAR, we have the TerraSAR-X, TanDEM-X, TECSAR from Israel, five SAR-Lupe satellites, and Radarsat-2. So we have now indeed sixteen and a new era for SAR remote sensing!
Earthzine: So you are the Principal Investigator on the TanDEM-X.
Alberto Moreira: In 2001 we started with the realization of TerraSAR-X satellite in Germany. And then in 2003, the national call for the next Earth Observation mission after TerraSAR-X was issued in Germany. I had the vision at that time: our institute should submit a strong proposal for a first interferometric SAR mission with close formation flying because of the huge demand for digital elevation models with improved quality. In 2006, we were very happy that the German space agency selected our mission proposal, TanDEM-X, for implementation. That was a challenge: A lot of changes could not be done as we would like because TerraSAR-X was almost built and scheduled to be launched in 2007. We started indeed in 2004-05 doing the kind of minimal changes in TerraSAR-X in order to allow for a bistatic radar operation. TerraSAR-X was launched in 2007 and TanDEM-X now in June 2010.
Earthzine: So it just launched recently.
Alberto Moreira: Very recently, but our team is so strong: three days after the launch, we produced our first radar image! This is a world record, normally it takes a few weeks or even months to have the first image. And just last week, 25 days after the launch of TanDEM-X we were able to produce our first DEM [digital elevation map] with a height accuracy of about 30 cm. Still, with a big separation between the satellites, as they are flying three seconds behind the other, this is more or less 20 kilometers. They are approaching very slowly and in the middle of October they will be just about 250 meters from each other!
Earthzine: What are the objectives of the TanDEM-X mission?
Alberto Moreira: The primary objective is to produce a new global digital elevation model with accuracy much better than what is currently available. Today what we have globally is about ten meters height accuracy. From SRTM we don’t have the icecaps, we only have DEM data within å±60 degree latitude because the shuttle could not cross the poles. With TanDEM-X we will have global coverage of consistent quality with horizontal spacing of about 12 meters and a height accuracy of 2 meters. For local areas, we can achieve accuracy that is even better than one meter in the height. For example, last week our first DEM had an accuracy of about 30 centimeters. Because the separation is so big, the interferometer becomes very sensitive. But we cannot map the whole Earth, for example the Himalayas, the Alps, or Rocky Mountains with accuracy of ten centimeters. That’s too sensitive: you lose control of the topography. In the first year, we’ll map the Earth with accuracy of about four meters. Then we’ll map it again the next year with much higher accuracy. The two products will deliver a high quality DEM with accuracy of about two meters.
Earthzine: Now, GEOSS is built around the nine societal benefit areas. What are the societal benefits of TanDEM-X?
Alberto Moreira: Basically, the global DEM, is the first goal of TanDEM-X. With this product we make contributions to the following 5 GEOSS benefit areas. One example is hydrology. Water flows according to the ground slope. If we use the present-day DEM’s ten meters accuracy to simulate waterflow, then you can see how inaccurate water modeling can be. Other benefit areas are disaster (e.g. high resolution 3D maps of affected areas), climate (topographic maps of the polar caps providing high-resolution information about the ice melting), agriculture (biomass estimation of crop fields by using the innovative technique of polarimetric SAR interferometry) and ecosystems (monitoring of forest areas, aforestation and deforestation). We are also planning to produce global maps on land use change since we are going to map the whole land masses twice.
Earthzine: How are you incorporating the TanDEM-X data sets with GEOSS?
Alberto Moreira: We are working in one of the GEOSS working groups that is also working with the SRTM DEM and with the ASTER DEM. The TanDEM-X mission was only possible because of a public-private partnership with the industry. Our industry partners paid 30% of the cost of the mission, and DLR the rest. We cannot open the whole DEM to the scientific community on a global basis because otherwise you don’t have a commercial market for the industry. We plan to make available to GEOSS a DEM with reduced pixel resolution but with height accuracy much better than currently available. This is how we have established industry partnerships so that we can do business as well as research and contribute to GEOSS.
Earthzine: What do you see are the top technical challenges to address over the next decade?
Alberto Moreira: Well we need to separate the technical challenges into categories such as lidars, imaging optical sensors, radars, and also microwave radiometers. In all these measurement areas we need to move in the direction of data continuity. Whether we are mapping long-term processes or short term, the measurements will only become reliable if there are data available over long periods. Radars, for example, digital beam forming represents the future technology, allowing a much better performance, swath width and resolution than existing systems. Microwave radiometers are moving towards the concept of synthetic aperture. The optical, high resolution, and several hyperspectral sensors are just coming out with an incredible number of bands.
One most important part is that these technologies must become affordable – remote sensing must be affordable. The cost of the satellites must become cheaper. We have good examples from Europe over the last few years where the industry makes offers much below the cost cap set by the funding agency. This is a revolution and I hope that in this way we can afford these new technological developments. We need solutions where the next generation of technology has a heritage from the past. We need a road map for 20 years ahead, so we can plan the heritage from one technology to another without big jumps that are usually associated with high risks and costs. Then technology development becomes affordable.
Earthzine: ESA just recently hosted the Living Planet Symposium. Do you view the Earth as a living entity?
Alberto Moreira: The Earth is dynamic. Every minute, every second something is changing on the Earth. Human beings make the Earth much more dynamic. This is a challenge because Earth’s processes are rather complicated and they interact with each other in ways we do not understand. One big challenge is to guarantee that we have sustainable development. The Earth is so fragile that if we don’t care, future generations will have less chance for a better life than we have. And this we cannot afford. Sustainable development is an agreement between countries, every nation has a responsibility to make sure that they are taking care of the water resources. Every individual has this responsibility. This is a living Earth. We have a responsibility to leave the Earth in at least as good of condition as it is today.
German Aerospace Center (DLR)
Microwaves and Radar Institute
P.O. Box 1116
Phone: + 49 8153 28 2305/2306
Fax: + 49 8153 28 1135