AGRISAR – Airborne SAR and Optic Campaigns

The Microwaves and Radar Institute initiated and has the lead of an extensive radar campaign with the Institute’s own airborne radar system (E-SAR) over a designated agricultural area with the support of the European Space Agency (ESA). The agricultural area is located in northern Germany and is conducted by a European Team. The main objective of the AGRISAR project is to collect data over a whole vegetation growth period starting with the soil cultivation until the harvesting of the crop. The campaign was intended to run for four months with a data collection of closely every week. Three main airborne remote sensing sensors are operated, the E-SAR system from DLR in Germany, maintained by the Microwaves and Radar Institute, the AHS from INTA in Spain, maintained by the Remote Sensing Laboratory and CASI from ITRES Research Limited in Canada. Simultaneously to each flight campaign ground measurements are collected.

Why do we need AGRISAR?

The need for food for an increasing population often threatens natural resources as people strive to get the most out of land already in production or push into virgin territory for new agricultural land. The damage is increasingly evident: water shortages; arable lands lost due to erosion, salinity, desertification, and urban spread; disappearing forests; and threats to biodiversity. The mistreatment of land recourses happen on small, regional and global scale, where the interconnections between land, water and atmosphere need to be seen as a holistic system in order to ensure sustainable management of natural resources.

One step of widening both the understanding and knowledge is the quantification of bio-/geophysical parameters of agricultural crops and the soil surface on which they are growing. This is essential if a decision or selection for agricultural cultivation practices need to be made. Therefore in forehead remote sensing (radar & optical data) are needed for the development and validation of models and retrieval algorithms.

The main objective of the proposed project is to build up a data base for the investigation and validation of the retrieval of bio-/geo-physical parameters, obtained at different radar frequencies (X-, C- and L-Band) and at thermal as well as hyperspectral optical bands acquired over vegetated and non-vegetated agricultural fields.

In addition the next generation of ESA Earth Observation satellites include a series of ‘Sentinel Missions’ to be developed and operated with the framework of GMES (Global Monitoring for Environment and Security). These will include SAR and optical satellites with new imaging configurations and spectral bands, and much improved capabilities for frequent repeat coverage.The AGRISAR 2006 campaign is required to address important specific programmatic needs of Sentinel-1 and -2:

• To assess the impact of Sentinel-1 and Sentinel-2 sensor and mission characteristics for land applications (land use mapping, parameter retrieval)
• To provide a basis for the quantitative assessment of sensor or mission trade-off studies, e.g. spatial and radiometric resolution, revisit time
• Simulate Sentinel-1 and Sentinel-2 image products over the land

In the context of Sentinel-1, AGRISAR 2006 is aimed primarily at the investigation of radar signatures throughout the crop growing season at time intervals of 7/10 days which are consistent with the mission concept. An important dataset of coordinated in-situ and airborne SAR measurements will be collected which will provide support both to studies of the Sentinel-1 technical concept, as well as contributing to studies of future mission concepts involving parameter retrieval at L-band.

As part of the refinement and verification of the Sentinel-1 technical concept, AGRISAR data will be used for the assessment of land use classification using the proposed nominal operating configuration (i.e. IW mode, VV + HH polarisation plus co-polarisation, weekly revisit). Simulation of Sentinel-1 image products is planned.

By including an optical data acquisition component, the campaign also aims to provide feedback on key issues relating to definition of the ESA Sentinel-2 multi-spectral mission requirements. Attention focuses on the investigation of the optimum position and width of spectral bands for land cover/change classification and retrieval of bio/geophysical parameters (e.g. improved surface classification, quantitative assessment of vegetation status at different crop growth stages). The imaging spectrometer data acquired as part of AGRISAR 2006 will be used to simulate Sentinel-2 L1b products using the different proposed configurations, and to investigate compatibility with the envisaged L2/L3 products.

Why choosing Görmin in northern Germany?

Demmin is a consolidated test site located in Mecklenburg-Vorpommern in North-East Germany, approximately 50km north of Neustrelitz and 150km north of Berlin. DLR’s German Remote Sensing Data Center (DFD) is cooperating with the farms in Demmin county (Mecklenburg – Western Pomerania) to operate the long-term test site DEMMIN. This test site is well established, having been used since 1999 as a test site for the so called DEMMIN Project (Durable Environmental Multidisciplinary Monitoring Information Network). The test site is based on a group of farms within a farming association covering approximately 25,000 ha. Görmin is the north-east part of the huge test site Demmin. The field sizes are very large in this area, in average 200 -250 ha. The main crops grown are winter wheat, winter barley, winter rape, maize and sugar beet. The altitudinal range within the test site is around 50m. The main attention of the huge area is paid to the Görmin farm in the north-eastern part of the test site. This farm uses advanced practice techniques and is open for the investigation of new methods, as an example they use GPS data for precision farming practices.

Which kinds of ground measurements are collected?

Simultaneously to the remote sensing data collection ground measurements samples are taken during the four month period. The ground sampling has been divided into a reduced continuously sampling strategy and an intensive sampling strategy taking place at three main weeks.

The continuous ground measurements are performed by DLR-DFD, ZALF, Geo-Informatik and the University of Kiel. They are collecting simultaneously soil and vegetation parameters to the airborne data acquisition on defined sample units.

The intensive campaign has been performed by the European AGRISAR team ( Italy, Spain, The Netherlands, Belgium, Denmark and Germany) at three times during the 14 weeks data acquisition period. At this intensive ground measurement weeks in addition to the continuous measured sampling units nearly all fields has been tried to cover with ground measurements. Whereas for the first intensive time period the measurement are dedicated to install fixed instruments (two soil moisture station and a Bowen-Ratio station) and to perform surface roughness measurements. The second and third are dedicated mainly to vegetation parameter measurements.

How has the remote sensing data been collected?

On a weekly basis the DLR’s Microwaves and Radar Institute’s airborne radar system (E-SAR) has collected a 10 km long and 3 km wide West-East flight stripe. In total 16 data acquisition flights has been conducted from mid April until the beginning of August 2006. Data in X-, C- and L-band has been acquired for each flight. At the intensive measurements campaign a second data acquisition flight stripe has been flown with an overlap in North-South direction.

At two intensive ground campaign, in June and July, for the two flight stripes also optical systems acquired data over the agricultural fields with the Canadian CASI from ITRES Research and the Spanish AHS from the National Institute for Aerospace Technology (INTA).

Which teams are involved?

The European team included German teams from DLR-HR, DLR-FB, DLR-DFD, ZALF, IG-Demmin and Universities in Munich, Berlin, Kiel and Jena along with Spanish teams from University of Valencia, University of Alicante and INTA, Italian teams from University of Naples and the National Research Council (ISSIA), teams from Canadian ITRES, from Technical University of Denmark, from University of Ghent in Belgium, from University of Canfield in UK and from the International Institute for Geo-Information Science and Earth Observation (ITC) in the Netherlands, along with participants from ESA.

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