Padsuren Tungalagsaikhan

Operational value-adding to AVHRR data over Europe : methods, results, and prospects

Abstract The German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) has been operating a ground segment for High Resolution Picture Transmission (HRPT) data acquisition, archiving, and distribution since the early 1980s. The stations visibility covers all of Europe. DFD started with the generation of thematic level-3 AVHRR value-added products consisting of Multichannel Sea Surface Temperatures (MCSST) and Normalized Difference Vegetation Indices (NDVI) in March 1993 [8]. Additionally, calibrated and registered 5-channel image subsets in two areas have been generated for supporting user-specific applications since 1994 [8]. The status of the current level-3 product generation chain as well as corresponding processing algorithms are presented. Perspectives are introduced to improve the existing products in terms of channel 1 and 2 radiometric optimization by implementing an atmospheric correction scheme, as well as to correct the solar channels for anisotropic reflectance with respect to different surfaces. As AVHRR data proved to be one of the major sources to derive global information on different land-oriented parameters, special emphasis is given in this paper on methods to extract land cover, the fraction of Absorbed Photosynthetic Active Radiation (fAPAR), and Leaf Area Index (LAI) with respect to operational use. Furthermore, different algorithms were discussed to derive Land Surface Temperatures (LST) by estimating surface emissivity based on NDVI time synthesis. First results over Germany are shown, problems addressed, and outlines for operational usage are given.

Possible contribution of satellite measurements to monitoring of air pollution in European cities and their surrounding areas for health services

Today there is broad agreement that populations health is significantly affected by influences from the polluted environment. Among the most tremendous consequences are allergies, skin cancer, and deseases of the respiratory tract. As a result of increasing frequence of such health problems health services started to initiate so-called environmental ambulances where patients get proper advice and treatment, especially in densely populated areas with severe air pollution problems. It turned out that the work of such ambulances can be strongly supported by delivering information on environmental conditions such as tropospheric ozone smog, aerosol particles and UV irradiance in near-real time. In such a way the medical staff is supplied with proper knowledge on the occurence of pollution events and their spatial distribution and detailed nature. The German Remote Sensing Data Center (DFD) receives data of different sensors on various satellite platforms and processes them into products of tropospheric ozone, the optical thickness and type of aerosol particles and UV intensity on 1-40 km grids. Satellite retrieved information itself can thus be a tool to monitor air quality and will directly be used by the environmental ambulance and other public health services. Furthermore, DFD extracts information about land use/land cover from its operational processing chains allowing the characterisation of ground pixels in terms of emissions of biogenic volatile organic compounds (BVOC) into the air. Air Pollution VIII, C.A. Brebbia, H. Power & J.W.S Longhurst (Editors)

Operational generation of AVHRR-based level-3 products at the German Remote Sensing Data Centre: status and perspectives

The German Remote Sensing Data Centre (DFD) of the German Aerospace Research Establishment (DLR) has been operating a ground segment for High Resolution Picture Transmission (HRPT) data acquisition, archiving, and distribution since the early 1980s. The stations visibility covers all of Europe. DFD started with the generation of thematic level-3 AVHRR value-added products consisting of Multichannel Sea Surface Temperatures (MCSST) and Normalized Difference Vegetation Indices (NDVI) in March 1993. Additionally, calibrated and registered 5-channel image subsets in two areas have been generated for supporting user-specific applications since 1994. The status of the current level-3 product generation chain as well as corresponding processing algorithms are presented. Perspectives to improve the existing products in terms of channel 1 and 2 radiometric optimization by implementing of a pre-operational atmospheric correction scheme developed by, as well as possibilities to correct the solar channels for anisotropic reflectance with respect to different surfaces are shown. Further, new level-3 products such as geophysical cloud parameters derived using the APOLLO algorithm are presented. Also, first results from various algorithm tests are presented to define an operational land surface temperature (LST) product by estimating surface emissivity based on NDVI time profiles.

Calibration and Pre-processing of a Multi-decadal AVHRR Time Series

Since the early 1980s, the German Remote Sensing Data Centre (DFD) of the German Aerospace Centre (DLR) has received archived and processed Advanced Very High Resolution Radiometer (AVHRR) data from the Polar Orbiting Environmental Satellites (POES) of the National Oceanic and Atmospheric Administration (NOAA). By December 2013, over 237,000 paths over Europe have since been archived at DLR. Based on these High Resolution Picture Transmission (HRPT) raw datasets, an operational pre-processing and value-adding chain has been developed (Dech et al., Aerosp Sci Technol 2(5):335–346, 1998; Tungalagsaikhan et al., Proc. 23th DGPF (12), 2003). In this chapter, the series of AVHRR sensors is introduced, and information on calibration and system correction procedures is given. Next, the pre-processing part of DLR’s processing chain is described, where focus is set on the calibration aspects. Time series examples are provided to show the influence of changes in calibration over time, and to illustrate the need for consistent pre-processing and data harmonization. According to these requirements DLR’s multi-decadal archive of AVHRR data will be re-processed in the frame of the TIMELINE project, providing consistent and well-calibrated time series data.

Towards an operational atmospheric correction for AVHRR land surface products

The German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) has been operating a ground segment for high resolution picture transmission (HRPT) data acquisition, archiving, and distribution since the early 1980s. Since 1994 daily normalized difference vegetation index (NDVI) synthesis maps for all of Europe have been derived from Advanced Very High Resolution Radiometer (AVHRR) measurements in near real-time with a horizontal resolution of about 1 km. In 1998 the processing chain has been expanded to European land surface temperatures (LST). Due to the presence and high variability of atmospheric ozone, water vapour and aerosols in time and space, the atmosphere significantly impacts the solar channels and results in erroneous NDVI data and noisy time series. A robust operational near real-time atmospheric correction scheme is presented. Until ENVISAT data is available, total ozone data derived from ERS-2 GOME and water vapour from NOAA-TOVS are considered for correction. An aerosol retrieval scheme based on GOME and ATSR data is currently being developed. For the determination of LST from the AVHRR brightness temperature measurements also an explicit correction of the atmospheric influence, mainly caused by water vapour absorption, is necessary. Therefore a simple split window technique is applied instead of a single channel method in terms of operational processing. The results have been validated over different sites in Germany, Egypt and Jordan.

The Integration of an Operational Fire Hot Spots Processing Chain in a Multi-Hazard Emergency Management Service Platform (PHAROS)

The project PHAROS (Project on a Multi-Hazard Open Platform for Satellite Based Downstream Services) designs and implements a multi-hazard open service platform which integrates space-based earth observation, satellite communications and navigation (Galileo/GNSS) assets to provide sustainable (pre-operational) services for a wide variety of users in multi-application domains, such as prediction/early detection of emergencies, population alerting, environmental monitoring and crisis management. While the service platform is designed to be multi-hazard, the specific developments for the pre-operational system and pilot demonstration will be focused on the forest fire scenario. The platform will integrate data from EO satellites and in-situ sensors process it and provide the results to a series of key services for disaster management in its different phases. One of the main concerns is to provide fire hot spots as an input for the PHAROS Simulation Service. These fire hot spots (thermal anomalies) are derived automatically and in near real time (NRT) from MODIS data. The MODIS data are available in a high (1d) temporal and in a medium (250m – 1000m) spatial resolution. For the detection of high temperature events (HTE) the MOD14 algorithm is used. The algorithm is based on the shift of the radiances/reflectance to shorter wavelengths (middle infrared) with an increasing surface temperature. MOD14 is well documented and tested in operational services and guarantees comparability and reproducibility as well as a standardized international acknowledged product. The thermal information is collected at 1000 m spatial resolution twice daily by each sensor (Terra and Aqua) providing up to four thermal observations daily. The MODIS images used for fire detection are acquired from two direct broadcast receiving stations from DLR located in Oberpfaffenhofen and Neustrelitz (Germany). This Poster will give an overview of the processing chain from the reception, the processing and derivation of the fire hot spots to the dissemination in the Pharos system.

Operational generation of AVHRR-based land surface temperatures (LST)-a new value adding product from the German Remote Sensing Data Center

The German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) has been receiving, archiving, and distributing high resolution picture transmission (HRPT) data since the early 1980s. The stations visibility covers Europe and its surroundings. DFD started the generation of thematic AVHRR value-added products consisting of multichannel sea surface temperatures (MCSST) and normalized difference vegetation indices (NDVI) in 1993. Calibrated and registered 5-channel image subsets of two areas have been generated for supporting regional applications since 1994. The improvement of the current products as well as the definition of new products has always been of major concern to DFD. The operational generation of land surface temperature (LST) based on estimated emissivity using NDVI time profiles has become operational in May 1998 and provides the user community with daily near-real-time (maximum delay 2 days) LST information for the whole of Europe. New AVHRR based level-3 products such as cloud parameters using the APOLLO algorithm developed by Saunders and Kriebel (1988) have been designed and are operationally generated and archived from January of 1998. A processing scheme for retrospective processing has been developed and will provide historical cloud data of central Europe from the early eighties. An overview is given of the current status of the products mentioned.

Operational determination of satellite derived sea surface temperature and wind speed from NOAA AVHRR and ERS SAR images

The intention of DLRs remote sensing activities is to provide the user community with geophysical information both on land and ocean surfaces in near real time with highest possible reliability on the thermatic quality. Towards this end, the German Remote Sensing Data Centre (DFD) as part of the Germanys aerospace research establishment (DLR) operates a High Resolution Picture Transmission (HRPT) Station for the operational acquisition of Advanced Very High Resolution Radiometer (AVHRR) data. Additionally, DFD functions as a national Processing and Archiving Facility (PAF) for ERS-1/2 data on behalf of ESA. Also, high resolution SAR data from ERS missions can be captured in near-real time by DLRs X-band facilities at the DFD in Neustrelitz, enabling operational derivation of maritime and climatological parameters. This paper describes the value adding processes for the operational derivation of Multichannel Sea Surface Temperatures (MCSST) from NOAA AVHRR data in order to generate daily, weekly and monthly temperature maps of the Mediterranean including the Black Sea, the northeastern Atlantic including the Baltic and North Seas, and the region around Madeira and the Canary Islands. Emphasis is given to special sensor processing steps such as calibration, navigation and cloud-screening for the available products. The ERS SAR is used to derive parameters such as mesoscale wind fields, currents and water levels for the needs of coastal management. Since the SAR works with the same wavelength as the scatterometer, the signal can be evaluated by the same algorithm used for the scayterometer signal (CMOD4 Algorithm from ESA). The wind direction is determined by a method that uses the average direction of wind rows visible on SAR images. Comparisons of wind measurements using recalibrated ERS SAR images to ground truth data are given. Finally, the application potential is outlined and network data distribution, including public access to all products via DLRs Intelligent Satellite Information System (ISIS), are described.