A concept for a regional coastal zone mission

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Ein Konzept für eine regionale Küstengewässermission

Aufgrund der Bevölkerungsexplosion gibt es einen weltweiten Konsens die Fernerkundung der Küstengebiete zu intensivieren, um so den wachsenden Einfluss der Menschheit auf das Küstenökosystem besser bewerten zu können (z.B. die Verschmutzung von Flussmündungen, Flutungen in kontaminierten Regionen). Doch im Gegensatz zu global ausgerichteten Fernerkundungsmissionen ist für die Beobachtung der Küstengewässer eine Mission mit regional-spezifischen Parametern notwendig. Aus diesem Grunde wurde im DLR, Berlin zusammen mit der Industrie und anderen Partnerforschungsinstituten eine Studie für eine Mission in einem erdnahen Orbit angefertigt. Im Rahmen dieser Studie wurden auch verschiedene technische Untersuchungen realisiert, wie eine Optik- und Gitter-Simulation, eine Signalrauschverhältnis-Analyse und ein experimenteller Prototypaufbau. In diesen Untersuchungen wurde gezeigt, dass ein neues abbildendes Spektrometer eine sehr gute VIS-NIR Komponente für eine Küstenfernerkundungsmission ist. In einer Modulanordnungsuntersuchung wurde das System Orbit-satellit Nutzlast optimiert in dem mehrere VIS-NIR Spektrometer, SWIR Kameras und ein TIR Scanner so angeordnet wurden, dass sie den wissenschaftlichen Anforderungen der internationalen Küstengewässer-Nutzergemeinschaft gerecht werden. Das vorgeschlagene Missionskonzept überdeckt das Spektralgebiet vom Sichtbaren zum Thermischen Infrarot in 21 teilweise programmierbaren Kanälen, mit einer relativ hohen räumlichen (100 m im VIS) und spektralen (1.5 nm im VIS) Auflösung. Für die Beobachtung von besonderen ökologischen Ereignissen ist eine hohe Wiederholungsrate (1-3 Tage) durch die Kippmöglichkeiten (ca. 30 deg von Nadir) des Minisatelliten (< 300 kg) sichergestellt.Due to increasing population pressure there is a world-wide concern to improve the observation of coastal zones for a better assessment of the growing impact of human being on the coastal ecosystem (e.g. pollution in river estuaries, flooding in contaminated regions). In contrast to globally oriented remote sensing missions, monitoring and management of rapid changes of the coastal ecosystem demand specific regional coastal zone mission features. Therefore a low-Earth orbit mission study has been carried out at DLR, Berlin together with industry and partner research institutes. In the scope of this study also various technical investigations have been performed, such as ray-tracing and grating simulations, a signal-to-noise model analysis and an experimental prototype set-up. Thus, the ability of a new imaging spectrometer has been demonstrated to fulfil the requirements for coastal zone observation. In a module arrangement analysis the system orbit-satellite-payload has been optimised in arranging VIS-NIR spectrometers, SWIR cameras and a TIR scanner in a way they cover best the science community needs. The resulting mission concept covers the spectral region from the visible to the thermal infrared in 21 partly programmable spectral channels, with a relatively high spatial (100 m in VIS) and spectral (1.5 nm in VIS) resolution. For monitoring of hazardous events a high repetivity (1-3 days) is ensured by the tilt capability (ca. 30 deg off nadir) of the mini satellite (< 300 kg)

A New Method to Retrieve the Data Requirements of the Remote Sensing Community – Exemplarily Demonstrated for Hyperspectral User NEEDS

User-driven requirements for remote sensing data are difficult to define,especially details on geometric, spectral and radiometric parameters. Even more difficult isa decent assessment of the required degrees of processing and corresponding data quality. Itis therefore a real challenge to appropriately assess data costs and services to be provided.In 2006, the HYRESSA project was initiated within the framework 6 programme of theEuropean Commission to analyze the user needs of the hyperspectral remote sensingcommunity. Special focus was given to finding an answer to the key question, “What arethe individual user requirements for hyperspectral imagery and its related data products?”.A Value-Benefit Analysis (VBA) was performed to retrieve user needs and address openitems accordingly. The VBA is an established tool for systematic problem solving bysupporting the possibility of comparing competing projects or solutions. It enablesevaluation on the basis of a multidimensional objective model and can be augmented withexpert’s preferences. After undergoing a VBA, the scaling method (e.g., Law ofComparative Judgment) was applied for achieving the desired ranking judgments. Theresult, which is the relative value of projects with respect to a well-defined main objective,can therefore be produced analytically using a VBA. A multidimensional objective modeladhering to VBA methodology was established. Thereafter, end users and experts wererequested to fill out a Questionnaire of User Needs (QUN) at the highest level of detail -the value indicator level. The end user was additionally requested to report personalpreferences for his particular research field. In the end, results from the experts’ evaluationand results from a sensor data survey can be compared in order to understand user needsand the drawbacks of existing data products. The investigation – focusing on the needs of the hyperspectral user community in Europe – showed that a VBA is a suitable method for analyzing the needs of hyperspectral data users and supporting the sensor/data specification-building process. The VBA has the advantage of being easy to handle, resulting in a comprehensive evaluation. The primary disadvantage is the large effort in realizing such an analysis because the level of detail is extremely high

A new method to retrieve the data requirements of the remote sensing community – exemplarily demonstrated for hyperspectral user NEEDS

User-driven requirements for remote sensing data are difficult to define, especially details on geometric, spectral and radiometric parameters. Even more difficult is a decent assessment of the required degrees of processing and corresponding data quality. It is therefore a real challenge to appropriately assess data costs and services to be provided. In 2006, the HYRESSA project was initiated within the framework 6 programme of the European Commission to analyze the user needs of the hyperspectral remote sensing community. Special focus was given to finding an answer to the key question, “What are the individual user requirements for hyperspectral imagery and its related data products?”. A Value-Benefit Analysis (VBA) was performed to retrieve user needs and address open items accordingly. The VBA is an established tool for systematic problem solving by supporting the possibility of comparing competing projects or solutions. It enables evaluation on the basis of a multidimensional objective model and can be augmented with expert’s preferences. After undergoing a VBA, the scaling method (e.g., Law of Comparative Judgment) was applied for achieving the desired ranking judgments. The result, which is the relative value of projects with respect to a well-defined main objective, can therefore be produced analytically using a VBA. A multidimensional objective model adhering to VBA methodology was established. Thereafter, end users and experts were requested to fill out a Questionnaire of User Needs (QUN) at the highest level of detail - the value indicator level. The end user was additionally requested to report personal preferences for his particular research field. In the end, results from the experts’ evaluation and results from a sensor data survey can be compared in order to understand user needs and the drawbacks of existing data products. The investigation – focusing on the needs of the hyperspectral user community in Europe – showed that a VBA is a suitable method for analyzing the needs of hyperspectral data users and supporting the sensor/data specification-building process. The VBA has the advantage of being easy to handle, resulting in a comprehensive evaluation. The primary disadvantage is the large effort in realizing such an analysis because the level of detail is extremely high

Spatial PSF nonuniformity effects in airborne pushbroom imaging spectrometry data

Efficient and accurate imaging spectroscopy data processing asks for perfectly consistent (i.e., ideally uniform) data in both the spectral and spatial dimensions. However, real pushbroom-type imaging spectrometers are affected by various point spread function (PSF) nonuniformity artifacts. First, individual pixels or lines may be missing in the raw data due to bad pixels originating from the detector, readout errors, or even electronic failures. Second, so-called smile and keystone optical aberrations are inherent to imaging spectrometers. Appropriate resampling strategies are required for the preprocessing of such data if emphasis is put on spatial PSF uniformity. So far, nearest neighbor interpolations have been often recommended and used for resampling. This paper shall analyze the radiometric effects if linear interpolation is used to optimize the spatial PSF uniformity. For modeling interpolation effects, an extensive library of measured surface reflectance spectra as well as real imaging spectroscopy data over various land cover types are used. The real measurements are systematically replaced by interpolated values, and the deviation between original and resampled spectra is taken as a quality measure. The effects of nearest neighbor resampling and linear interpolation methods are compared. It is found that linear interpolation methods lead to average radiometric errors below 2% for the correction of spatial PSF nonuniformity in the subpixel domain, whereas the replacement of missing pixels leads to average errors in the range of 10%–20%

A concept for a Regional Coastal Zone Mission

Recently, applicational and technological studies have been performed by a group of scientists and industry, led by DLR, basing on experiences with ocean-colour sensor MOS-IRS. The result is a new low-cost mission concept with special emphasis on coastal-zone remote sensing, which will be able to fill an imported gap in Earth observation data, i.e. to detect the strongly needed data for a better understanding of the rapid changes of coastal areas and to provide a tool for monitoring catastrophical hazards. The proposed low-budget mission ECOMON (Regional Ecological Research and Monitoring) will provide visible to the thermal infrared data with relatively high spectral (1.4 nm) and spatial resolution (100 m). The VISSWIRTIR spectral region will be covered by 16 selectable channels in the visible, four channels in the SWIR, and one in the TIR. The swath width will be 400 km and a off-nadir tilting possibility ensures a high repetition rate of two days (for latitudes &gt; 30°). Using mainly compact off-the-shelf technology and carrying this payload on a mini-satellite can ensure a low-budget mission with adequate performance for coastal zone observation

Constitution of an automized processing chain to analyse a MERIS time series of Swiss lakes

The physically based Modular Inversion & Processing System (MIP) is used in an automized processing chain for inland water constituent retrieval from MERIS level 1B data. Preprocessing routines are used to automatically convert the ESA generic data products into MIP input data format. Water/land masking, atmospheric correction and water constituent retrieval are accomplished by simple batch executables from MIP. The accuracy of the constituent retrieval mainly depends on the spectral fit between the image input data and the radiative transfer model results extracted from a database. Therefore, thresholds and initial values for model fitting have to account for all occurring lake specific temporal variations and need careful adjustment

Calibration Facility for Airborne Imaging Spectrometers

ESA currently builds the airborne hyper-spectral push broom imaging spectrometer APEX (Airborne Prism EXperiment) operating in the spectral range from 380 to 2500 nm. The APEX instrument will only achieve its challenging measurement accuracy by regular calibration of the instrument between flight cycles. In view of the high relevance to scientific objectives, ESA is funding an "Calibration Home Base" (CHB) for APEX. It is located at DLR Oberpfaffenhofen and will be operational from 2006 on. The CHB provides all hard- and software tools required for radiometric, spectral and geometric on-ground characterisation and calibration of the instrument and its internal references and on-board attachments, and to perform measurements on polarisation- and straylight-sensitivity. This includes a test bed and the provision of the infrastructure