Showing papers in "Remote Sensing in 2007"

The marine optical buoy (MOBY) radiometric calibration and uncertainty budget for ocean color satellite sensor vicarious calibration

Abstract: For the past decade, the Marine Optical Buoy (MOBY), a radiometric buoy stationed in the waters off Lanai, Hawaii, has been the primary in-water oceanic observatory for the vicarious calibration of U. S. satellite ocean color sensors, including the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the Moderate Resolution Imaging Spectrometers (MODIS) instruments on the National Aeronautics and Space Administration's (NASA's) Terra and Aqua satellites. The MOBY vicarious calibration of these sensors supports international effort to develop a global, multi-year time series of consistently calibrated ocean color data products. A critical component of the MOBY program is establishing radiometric traceability to the International System of Units (SI) through standards provided by the U. S. National Institute of Standards and Technology (NIST). A detailed uncertainty budget is a core component of traceable metrology. We present the MOBY uncertainty budget for up-welling radiance and discuss additional considerations related to the water-leaving radiance uncertainty budget. Finally, we discuss approaches in new instrumentation to reduce the uncertainties in in situ water-leaving radiance measurements.

Scintillation index of optical plane wave propagating through non-Kolmogorov moderate-strong turbulence

Abstract: An optical plane wave propagating through atmospheric turbulence is affected by irradiance fluctuations known as scintillation The scintillation index of an optical wave in strong turbulence can be analyzed by extended Rytov theory, which uses filter functions to eliminate the effect of cell turbulence sizes that do not contribute to scintillation, and it already has been calculated by Kolmogorov's power spectral density model However several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly In this paper, for a horizontal path, we use extended Rytov theory to carry out plane wave scintillation index analysis in non Kolmogorov strong turbulence We do it using a non Kolmogorov power spectrum which uses a generalized exponent factor and a generalized amplitude factor Although our final expressions for the scintillation have been obtained by extended Rytov theory, which is necessary to adopt in strong turbulence conditions, they reduce to the proper results also in weak turbulence

The Microwave Humidity Sounder (MHS): in-orbit performance assessment

Abstract: The Microwave Humidity Sounder (MHS) is the high-frequency microwave radiometer of the ATOVS (Advanced TIROS Operational Vertical Sounder) instrument suite of the IJPS (Initial Joint Polar System), the current joint EUMETSAT-NOAA programme for operational satellite meteorology. Five MHS models have been built by Astrium Ltd under EUMETSAT contract, two of which are currently operational on the NOAA-18 and Metop-A satellites. The MHS instrument replaces the former AMSU-B in the operational microwave sounder suite. This paper provides a summary description of the MHS instrument and describes in some detail its in-orbit performance and functionality, along with a comparison with similar instruments. The in-orbit performance has been extensively assessed during the SIOV (Satellite In-Orbit Verification), the first part of the commissioning phase aimed at activating the payload and verifying its operation, and is periodically monitored throughout the mission life. The performance relevant to the SIOV and operational phase of the MHS instruments on both NOAA-18 and Metop-A are presented. With respect to its predecessor AMSU-B, the MHS instrument constitutes a sensible improvement in terms of radiometric sensitivity and calibration accuracy, while allowing full continuity of the acquired data and relevant processing.

Sea surface effects on the sea surface temperature estimation by remote sensing

Abstract: By using a sea surface temperature profiler buoy, the behaviour of the vertical temperature profile near the sea surface was observed in Mutsu Bay. In the daytime under calm and strong sunshine condition, there occurred a large temperature difference between the uppermost sea surface and the 1 m depth. The difference disappeared when the wind began to blow with a speed greater than 4ms−1. Besides the atmospheric effects the inhomogeneity of the vertical temperature distribution near the sea surface must be another major error factor in the sea surface temperature estimation by satellite remote sensing.

Sea surface temperature (AVHRR, MODIS) and ocean colour (MODIS) seasonal and interannual variability in the Macaronesian islands of Azores, Madeira, and Canaries

Abstract: Within the framework of ORPAM (03/MAC/4.2/A2) project, five years of AVHRR Sea Surface Temperature (SST) (in °C) (2001-2006) (HAZO station, Azores) and of MODIS Ocean Colour (OC) (chlorophyll a in mg m-3) and SST (2002- 2007) data (NASA/GSFC), allowed the establishment and comparison of the mean surface temporal variability among the Azores, Madeira, and Canaries regions. Results show strong and similar seasonal SST variability patterns with average values ranging between 15°C (winter) and 27°C (summer). Largest SST differences are observed during wintertime (Azores/Canaries-lowest/highest values, respectively). Interannual SST variability shows no defined patterns among the three regions. Ocean Colour seasonal variability varies inversely with SST. In the Azores, spring blooms dominate, followed sometimes by smaller autumn ones. In Madeira, spring blooms dominate. In Canaries, OC means are highest during February and March. Interannual OC variability shows the largest variation in Canaries (summertime). These results suggest strong latitudinal gradient effects. Canaries waters are generally warmest, followed by Madeira, and Azores. Highest OC averages are found in the Azores and Canaries regions. In the latter case, this most likely reflects e.g.: the contribution of the African coastal upwelling; OC algorithms failure in Case 2 waters; and winter mixing processes in the region.

Characterization and Correction of Stray Light in Optical Instruments

Abstract: Improperly imaged, or scattered, optical radiation within an instrument is difficult to properly characterize and is often the dominant residual source of measurement error. Scattered light can originate from the spectral components of a "point" source and from spatial elements of an extended source. The spectral and spatial scattered light components are commonly referred to as stray light and can be described by an instrument's spectral line spread function (SLSF) and point spread function (PSF), respectively. In this paper, we present approaches that characterize an instrument's response to scattered light and describe matrices that have been developed to correct an instrument's response for this scattered light. Examples are given to demonstrate the efficacy of the approach and implications for remote sensing instruments are discussed.

ECSIM : The simulator framework for EarthCARE

Abstract: In 2013 an important ESA Core Explorer Mission, EarthCARE is scheduled to be launched. EarthCARE, (the Earth, Clouds, Aerosol and Radiation Explorer) will comprise two active (a cloud-profiling radar (CPR) and an high spectral resolution atmospheric lidar (ATLID)) and two passive (a Multi-spectral imager (MSI) and a Broad-Band Radiometer (BBR)) instruments. With these, EarthCARE will enable cloud and aerosol properties retrievals consistent with a Top-of-Atmospheric (TOA) flux accuracy of 10 Wm-2. This will be achieved by simultaneously probing the atmosphere vertically with the active instruments in synergy with the passive instruments. In order to facilitate and optimize algorithm development and to quantify the effect of different instrument configurations on the mission performance a simulator for EarthCARE (ECSIM) has been developed. ECSIM relies strongly upon a previous prototype developed by ESA/KNMI where a combination of forward and retrieval models (full End-to-End capabilities) have been included. In order to make this tool more useful within the scientific and engineering communities, the prototype simulator has been embedded into a completely reorganized architecture intended to improve a number of aspects: *Complex algorithms have been enclosed within logical entities: models. *Models are connected in a logical sequence with well-defined interfaces. *Users can customize almost every mode's parameter values using configuration XML files. *Model outputs are well documented and stored in easy to access NetCDF files. *Complex simulations can be built up with a few mouse clicks. *Users can run lengthy simulations automatically iterating through different parameter values. *ECSIM can intercept and classify information and error messages from the simulations. *A database is maintained with all the information generated by the system. *It is possible to add third-party algorithms or tools to convert, analyze and visualize data extracted from generated products.

Improved minimal inter-quantile distance method for blind estimation of noise variance in images

Abstract: Multichannel (multi and hyperspectral, dual and multipolarization, multitemporal) remote sensing (RS) is widely used in different applications. Noise is one of the basic factors that deteriorates RS data quality and prevents retrieval of useful information. Because of this, image pre-filtering is a typical stage of multichannel RS data pre-processing. Most efficient modern filters and other image processing techniques employ a priori information on noise type and its statistical characteristics like variance. Thus, there is an obvious need in automatic (blind) techniques for determination of noise type and its characteristics. Although several such techniques have been already developed, not all of them are able to perform appropriately in cases when considered images contain a large percentage of texture regions and other locally active areas. Recently we have designed a method of blind determination of noise variance based on minimal inter-quantile distance. However, it occurred that its accuracy could be further improved. In this paper we describe and analyze several ways to do this. One opportunity deals with better approximation of inter-quantile distance curve. Another opportunity concerns the use of image pre-segmentation before forming an initial set of local estimates of noise variance. Both ways are studied for model data and test images. Numerical simulation results confirm improvement of estimate accuracy for the proposed approach.

A laser sounder for measuring atmospheric trace gases from space

Abstract: Mounting concern regarding global warming and the increasing carbon dioxide (CO 2 ) concentration has stimulated interest in the feasibility of measuring CO 2 mixing ratios from space. Precise satellite observations with adequate spatial and temporal resolution would substantially increase our knowledge of the atmospheric CO 2 distribution and allow improved modeling of the CO 2 cycle. Current estimates indicate that a measurement precision of better than 1 part per million (1 ppm) will be needed in order to improve estimates of carbon uptake by land and ocean reservoirs. A 1-ppm CO 2 measurement corresponds to approximately 1 in 380 or 0.26% long-term measurement precision. This requirement imposes stringent long-term precision (stability) requirements on the instrument In this paper we discuss methods and techniques to achieve the 1-ppm precision for a space-borne lidar.

Radiometric calibration status of Landsat-7 and Landsat-5

Abstract: Launched in April 1999, Landsat-7 ETM+ continues to acquire data globally. The Scan Line Corrector in failure in 2003 has affected ground coverage and the recent switch to Bumper Mode operations in April 2007 has degraded the internal geometric accuracy of the data, but the radiometry has been unaffected. The best of the three on-board calibrators for the reflective bands, the Full Aperture Solar Calibrator, has indicated slow changes in the ETM+, but this is believed to be due to contamination on the panel rather then instrument degradation. The Internal Calibrator lamp 2, though it has not been used regularly throughout the whole mission, indicates smaller changes than the FASC since 2003. The changes indicated by lamp 2 are only statistically significant in band 1, circa 0.3% per year, and may be lamp as opposed to instrument degradations. Regular observations of desert targets in the Saharan and Arabian deserts indicate the no change in the ETM+ reflective band response, though the uncertainty is larger and does not preclude the small changes indicated by lamp 2. The thermal band continues to be stable and well-calibrated since an offset error was corrected in late-2000. Launched in 1984, Landsat-5 TM also continues to acquire global data; though without the benefit of an on-board recorder, data can only be acquired where a ground station is within range. Historically, the calibration of the TM reflective bands has used an onboard calibration system with multiple lamps. The calibration procedure for the TM reflective bands was updated in 2003 based on the best estimate at the time, using only one of the three lamps and a cross-calibration with Landsat-7 ETM+. Since then, the Saharan desert sites have been used to validate this calibration model. Problems were found with the lamp based model of up to 13% in band 1. Using the Saharan data, a new model was developed and implemented in the US processing system in April 2007. The TM thermal band was found to have a calibration offset error of 0.092 W/m2 sr µm (0.68K at 300K) based on vicarious calibration data between 1999 and 2006. The offset error was corrected in the US processing system on April 2007 for all data acquired since April 1999.

Integrated Cloud-Aerosol-Radiation Product using CERES, MODIS, CALIPSO and CloudSat Data

Abstract: This paper documents the development of the first integrated data set of global vertical profiles of clouds, aerosols, and radiation using the combined NASA A-Train data from the Aqua Clouds and Earth's Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and CloudSat. As part of this effort, cloud data from the CALIPSO lidar and the CloudSat radar are merged with the integrated column cloud properties from the CERES-MODIS analyses. The active and passive datasets are compared to determine commonalities and differences in order to facilitate the development of a 3-dimensional cloud and aerosol dataset that will then be integrated into the CERES broadband radiance footprint. Preliminary results from the comparisons for April 2007 reveal that the CERES-MODIS global cloud amounts are, on average, 0.14 less and 0.15 greater than those from CALIPSO and CloudSat, respectively. These new data will provide unprecedented ability to test and improve global cloud and aerosol models, to investigate aerosol direct and indirect radiative forcing, and to validate the accuracy of global aerosol, cloud, and radiation data sets especially in polar regions and for multi-layered cloud conditions.

Evaluation of the surface of objects by use of Minnaert constants

Abstract: Minnaert constants are calculated from the intensity of the light scattered from the surface of objects. Focused on remote sensing of vegetation on the earth's surface, the light reflected from leaves is measured. A remote sensing simulator is used in an experimental room with a halogen lamp as an optical source and a Wratten gelatin filter No. 25 as a filter. Bidirectional reflectance from two kinds of leaves with different degrees of roughness is measured and their Minnaert constants are obtained by recurrent analysis of the results. The Minnaert constant for a leaf with a smooth surface is larger than 1 (Lambertian surface) and that with a rough surface is smaller than 1.

Five years of AMSR-E monitoring and successive GCOM-W1/AMSR2 instrument

Abstract: Japan Aerospace Exploration Agency (JAXA) has been proposing the Global Change Observation Mission (GCOM). GCOM will consist of two series of medium size satellites: GCOM-W (Water) and GCOM-C (Climate). The mission will take over the Advanced Earth Observing Satellite-II (ADEOS-II or Midori-II). The GCOM-W1 satellite (the first generation of GCOM-W series) was approved by the Space Activities Commission of Japan to proceed to the development phase. Current target of launch date is the beginning of 2012. The Advanced Microwave Scanning Radiometer-2 (AMSR2) is sole mission instrument onboard the GCOM-W1 satellite. Although the simultaneous observation by a microwave scatterometer and AMSR2 is still desired, installation of the scatterometer is not the case at least for the GCOM-W1 satellite. AMSR2 is a successor of the AMSR for the EOS (AMSR-E) provided to the NASA Aqua satellite and AMSR onboard Midori-II with some improvements based on the experiences of AMSR and AMSR-E. They include an improvement of calibration system and an addition of 7.3 GHz channels to help mitigating radio-frequency interference issue. The AMSR-E instrument is still providing continuous data records more than 5-years. Observed brightness temperatures and retrieved geophysical parameters are being widely used for monitoring environmental changes and for applying to the operational applications such as numerical weather forecasting. We expect a long-term continuity by leading the GCOM-W/AMSR2 to the AMSR-E observation.

Applications and results of MODIS lunar observations

Abstract: Since launch, both Terra and Aqua MODIS have been making regular lunar observations with a primary objective of providing an independent stability monitoring for the reflective solar bands (RSB) calibration. To a large extent, this approach is based on the fact that the Moon has extremely stable surface reflectance properties. When combined with a lunar radiometric model, the applications of lunar observations can be significantly enhanced. Using MODIS as an example, this paper discusses various applications developed from its lunar observations. In addition to the RSB stability monitoring, MODIS lunar observations are regularly used to examine its calibration consistency between Terra and Aqua MODIS and to track the sensor's band-to-band registration (BBR) stability. Examples also presented in this paper include optical leak and electronic crosstalk characterization for MODIS thermal emissive bands (TEB) and shortwave infrared (SWIR) bands. Results from multi-year lunar observations show that the MODIS RSB calibration stability has been satisfactory when compared to its solar calibration, and that Terra and Aqua MODIS are calibrated consistently to within ±1% for most RSB. The spatial characterization results derived from MODIS lunar observations agree very well with that determined from its on-board calibrator. It is clear that the applications and results of MODIS lunar observations presented here will serve as good examples or references for other sensors that also make use of lunar surface observations.

Becoming a NIR-Sensitive Aerial Archaeologist

Abstract: For various reasons, aerial archaeologists use(d) film when studying their objects in the Near InfraRed (NIR). However, even the use of colour InfraRed (CIR) emulsions remained severely restricted till today due to some ignorance or a severe lack of knowledge about the subject and - not at least - the critical imaging process. This error-prone film-based workflow belongs now to the past, thanks to the advent of digital cameras. In this article, two new approaches will be outlined, both in an attempt to overcome the constraints on the common archaeological interpretation of varying visible colours in vegetation: the use of modified hand-held digital cameras to photograph the NIR spectrum on the one hand, as well as future plans to digitally capture both Red and NIR wavelengths simultaneously on the other. Besides additional technical background information on NIR photography, the paper treats the advantages (and disadvantages) of NIR to normal archaeological aerial imaging. In the end, an introduction of a new, remotely controlled system to support (aerial) archaeologists in their (NIR) photography is given together with several approaches to NIR image processing.

Stratospheric and upper tropospheric aerosol retrieval from limb scatter signals

Abstract: Solar occultation observations made by the SAGE family of space instruments have provided a record of global stratospheric and upper tropospheric aerosols that extends over 25 years. Since the demise of SAGE II and SAGE III however, there are presently no space instruments devoted to continuing this aerosol data set. The paper aims to demonstrate that aerosol extinction profiles, together with a moment of the size distribution, can be accurately retrieved from Limb Scatter measurements. The methodology is described, and retrieval examples are presented using data from a Limb Scatter instrument, namely SAGE III. The retrieved extinction profiles are compared with SAGE II and SAGE III occultation aerosol products for a series of wavelengths. It is shown that the relative retrieval accuracy is good (less than 5%), with a relative precision on the order of 25%. Once operational, it is planned to apply the retrieval method to the data collected by the two still-operating Limb Scatter instruments (namely OSIRIS and SCIAMACHY) in order to extend the aerosol data record into the present time. In the future, the OMPS Limb Profiler instrument, which is presently manifested on NPP with a launch date of September 2009, will be used for additional stratospheric aerosol research.

EARLINET correlative measurements for CALIPSO

Abstract: The European Aerosol Research Lidar Network (EARLINET) was established in 2000 to derive a comprehensive, quantitative, and statistically significant data base for the aerosol distribution on the European scale. At present, EARLINET consists of 25 stations: 16 Raman lidar stations, including 8 multi-wavelength Raman lidar stations which are used to retrieve aerosol microphysical properties. EARLINET performs a rigorous quality assurance program for instruments and evaluation algorithms. All stations measure simultaneously on a predefined schedule at three dates per week to obtain unbiased data for climatological studies. Since June 2006 the first backscatter lidar is operational aboard the CALIPSO satellite. EARLINET represents an excellent tool to validate CALIPSO lidar data on a continental scale. Aerosol extinction and lidar ratio measurements provided by the network will be particularly important for that validation. The measurement strategy of EARLINET is as follows: Measurements are performed at all stations within 80 km from the overpasses and additionally at the lidar station which is closest to the actually overpassed site. If a multi-wavelength Raman lidar station is overpassed then also the next closest 3+2 station performs a measurement. Altogether we performed more than 1000 correlative observations for CALIPSO between June 2006 and June 2007. Direct intercomparisons between CALIPSO profiles and attenuated backscatter profiles obtained by EARLINET lidars look very promising. Two measurement examples are used to discuss the potential of multi-wavelength Raman lidar observations for the validation and optimization of the CALIOP Scene Classification Algorithm. Correlative observations with multi-wavelength Raman lidars provide also the data base for a harmonization of the CALIPSO aerosol data and the data collected in future ESA lidar-in-space missions.

Active pixel sensors: the sensor of choice for future space applications?

Abstract: It is generally known that active pixel sensors (APS) have a number of advantages over CCD detectors if it comes to cost for mass production, power consumption and ease of integration. Nevertheless, most space applications still use CCD detectors because they tend to give better performance and have a successful heritage. To this respect a change may be at hand with the advent of deep sub-micron processed APS imagers (< 0.25-micron feature size). Measurements performed on test structures at the University of Delft have shown that the imagers are very radiation tolerant even if made in a standard process without the use of special design rules. Furthermore it was shown that the 1/f noise associated with deep sub-micron imagers is reduced as compared to previous generations APS imagers due to the improved quality of the gate oxides. Considering that end of life performance will have to be guaranteed, limited budget for adding shielding metal will be available for most applications and lower power operations is always seen as a positive characteristic in space applications, deep sub-micron APS imagers seem to have a number of advantages over CCD's that will probably cause them to replace CCD's in those applications where radiation tolerance and low power operation are important

Design challenge on forthcoming SGLI boarded on GCOM-C

Abstract: The Japan Aerospace Exploration Agency (JAXA) has the plan of the Global Change Observation Mission (GCOM) for monitoring global environmental change. Second generation Global Imager (SGLI) is a mission instrument to be installed on the satellite of GCOM Mission Climate (GCOM-C) satellite. SGLI is the optical radiometer observed to the frequent Global, Ocean, Land, Cloud and Ice sphere to help determine the Earth's climate change. SGLI is a suite of two radiometers called VNR and IRS. The VNR is employing a wide swath (1150km) push-bloom scan with line CCD detector. IRS is employing a conventional cross-track mirror scan system (1400km swath) with cooled infrared detector. We report the SGLI preliminary design and special feature. The current SGLI is BBM development phase which is underway to confirm the feasibility of the design.

Ship traffic monitoring using satellite SAR images in combination with AIS reports

Abstract: Ship traffic monitoring may be performed using satellite SAR data. The advantage with the SAR sensor is the all weather and day/night imaging capability. However, the SAR backscatter contrast between a vessel and the surrounding sea state may be small in high wind conditions and at small incidence angles. The present and future SAR satellites will have the capability of imaging the earth surface with several incidence angles, and with dual-polarimetry (HH/HV, VV/VH or HH/VV). The SAR ship/clutter contrast may threrefore be increased by applying different polarisation combinations, or using higher incidence angles. We have shown that geocoded ENVISAT ASAR images in the coastal region of Norway can be used to gain experience in the combined use of satellite SAR and an automatic identification system (AIS) for ship traffic monitoring. There are plans for placing AIS systems onboard satellites. It will then be possible to fuse the information from satellite SAR with those from satellite (or ground-based coastal) AIS and thereby identify all the detected ships within a SAR image. This data fusion will enable us to develop further knowledge about SAR backscatter properties from vessel types that may not be detected so well using the SAR data only. On the other side, it will be possible to pin-point those ship candidates that do not carry an AIS system, and thereby take appropriate security or rescue actions.

Wave front sensing of an optical vortex and its correction in the close-loop adaptive system with bimorph mirror

Abstract: The sensing of phase front of the vortex laser beam has been carried out with the help of a Hartmann-Shack sensor. The vortex beam is generated in the form of a Laguerre-Gaussian beam ( LG 0 1 mode) with the help of the special helicoidal phase plates manufactured by the kinoform technology. The measured shifts of focal spots on the hartmannogram are compared with the calculated shifts. From the measured wave front tilts the reconstruction of singular phase surface has been performed with using the novel reconstruction technique. The removing of phase singularity from an optical vortex is demonstrated in the close-loop adaptive system including the bimorph deformable piezoceramics-based mirror.

Deployable, lightweight, and large aperture spaceborne telescope for lidar-based earth observations

Abstract: This paper describes an innovative approach for a new generation of large aperture, deployable telescopes for advanced space LIDAR applications, using the thin active mirror technology. The overall telescope design is presented with a special attention to the optical performances analysis. The mechanical layout with details of the deployment and baffling technique is shown; the complete satellite thermo-elastic analysis mapping the primary mirror deformation due to the thermal loads is presented; the control system architecture is explained and the optical design including the angular and spatial resolution, effective optical aperture and radiometric transmission, optical alignment tolerances, straylight and baffling is deeply discussed. Finally an overview of different mission profiles that this technology can satisfy is presented; the imaging performances can be achieved using the shown technology tuning the surface control to higher performances.

Detection and feature extraction of bridges in airborne and spaceborne SAR image data

Abstract: Operational SAR satellite systems such as ENVISAT-ASAR and RADARSAT-1 deliver image data of a rather coarse resolution, which allows the recognition or feature extraction only for large man-made objects State of the art airborne SAR sensors on the other hand provide spatial resolution in the order well below a half meter In such data many features of urban objects can be identified and used for recognition Core elements of man-made infrastructure are bridges In case of bridges over water, the oblique side looking imaging geometry of SAR sensors may lead to special signature in a SAR image depending on the aspect In this paper, the appearance of bridges over water in SAR data is discussed Geometric constraints concerning the changing of this signature are investigated using simulation techniques based on an adapted ray tracing Furthermore, an approach is presented to detect bridges over water and to derive object features from spaceborne and airborne SAR images in the context of disaster management RADARSAT-1 data with a spatial resolution of about 9 m as well as high-resolution airborne SAR data of geometric sampling distance better than 40 cm are investigated

AlGaN-based focal plane arrays for selective UV imaging at 310nm and 280nm and route toward deep UV imaging

Abstract: The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet detection. Such camera present an intrinsic spectral selectivity and an extremely low dark current at room temperature. It can compete with technologies based on photocathodes, MCP intensifiers, back thinned CCD or hybrid CMOS focal plane arrays (FPA) for low flux measurements. AlGaN based cameras allow UV imaging without filters or with simplified ones in harsh solar blind conditions. Few results on camera have been shown in the last years, but the ultimate performances of AlGaN photodiodes couldn't be achieved due to parasitic illumination of multiplexers, responsivity of p layers in p-i-n structures, or use of cooled readout circuit. Such issues have prevented up to now a large development of this technology. We present results on focal plane array of 320x256 pixels with a pitch of 30μm for which Schottky photodiodes are multiplexed with a readout circuit protected by black matrix at room temperature. Theses focal plane present a peak reponsivity around 280nm and 310nm with a rejection of visible light of four decades only limited by internal photoemission in contact. Then we will show the capability to outdoor measurements. The noise figure is due to readout noise of the multiplexer and we will investigate the ultimate capabilities of Schottky diodes or Metal- Semiconductor-Metal (MSM) technologies to detect extremely low signal. Furthermore, we will consider deep UV measurements on single pixels MSM from 32nm to 61nm in a front side illumination configuration. Finally, we will define technology process allowing backside illumination and deep UV imaging.

An approach for GIS-based statistical landslide susceptibility zonation: with a case study in the northern part of El Salvador

Abstract: The present study deals with evaluation of landslide prone zones in the northern part of El Salvador. The study area falls onto a tectonically and seismically active zone of Central America with on-going neo-tectonic activities. Focus has been put on applying the technique that allows a fast assessment of large regions. The analysis was based on digital data sets including various derivatives of digital elevation models (DEMs) as well as Landsat-based information such as micro-lineament density and landcover; seismic database, geological and morphological maps. Spatial multi-layered information has been used for landslide susceptibility analysis. Here, an inventory map of 363 landslides induced in 1998 by hurricane Mitch were used to produce a dependent variable, the statistical hazard analysis has been carried out while the zonal statistics was used to assign the weights for individual classes of the studied factors. Thus, all the relevant thematic layers representing various independent factors (slope, aspect, relative relief, lithology, drainage density, micro-lineament density and land cover) were relatively weighted and classified due to its disposition to cause landslides. Principle Component Analyses (PCA) was used as a multivariate statistical method that allowed decorrelation of the individual hazard triggers. It has been observed that the high potential zones were found to have very high lineament density, high relative relief and drainage density areas. On the young volcanic pyroclastic deposits, heavy rainfall and sparse vegetation cover cause persistent recurrence of landslides along this region. As result, a landslide susceptibility map integrating morphological, lithological and hydrological information was computed. Delineated hazard zones were again validated with the landslide inventory map and both, the model and terrain mapping, showed a good agreement as the highest class occupied the 64% of the landslide areas and the two highest classes together occupied 90% of the landslide areas, on the other hand none of the landslides fell into the lowest class.

Change detection in urban scenes by fusion of SAR and hyperspectral data

Abstract: Urban areas are rapidly changing all over the world and therefore provoke the necessity to update urban maps frequently. Remote sensing has been used for many years to monitor these changes. The urban scene is characterized by a very high complexity, containing objects formed from different types of man-made materials as well as natural vegetation. Hyperspectral sensors provide the capability to map the surface materials present in the scene using their spectra and therefore to identify the main object classes in the scene in a relatively easy manner. However ambiguities persist where different types of objects are constructed of the same material. This is for instance the case for roads and roof covers. Although higher-level image processing (e.g. spatial reasoning) might be able to relief some of these constraints, this task is far from straight forward. In the current paper the authors fused information gathered using a hyperspectral sensor with that of high-resolution polarimetric SAR data. SAR data give information about the type of scattering backscatter from an object in the scene, its geometry and its dielectric properties. Therefore, the information obtained using the SAR processing is complementary to that obtained using hyperspectral data. This research was applied on a dataset consisting of hyperspectral data from the HyMAP sensor (126 channels in VIS-SWIR) and E-SAR data which consists of fullpolarimetric L-band and dual-polarisation (HH and VV) X-band data. Two supervised classifications are used; 'Logistic Regression' (LR) which applied to the SAR and the PolSAR data and a 'Matched Filter' which is applied to the hyperspectral data. The results of the classification are fused in order to improve the mapping of the main classes in the scene and were compared to a ground truth map that was constructed by combining a digital topographic map and a vectorized cadastral map of the research area. An adequate change detection of man-made objects in urban scenes was obtained by the fusion of features derived from SAR, PolSAR and hyperspectral data.

Remote sensing of precipitable water vapour and cloud cover for site selection of the European Extremely Large Telescope (E-ELT) using MERIS

Abstract: Remotely sensed data can be of great interest for the site selection of astronomical observatories. In particular, candidate sites of the future European Extremely Large Telescope (E-ELT) of 30-60 m diameter from ESO need to be assessed and analytically compared in their observing characteristics. Parameters such as cloud cover and precipitable water vapor which are important for optical and infrared astronomical observations have been assessed with the MEdium Resolution Imaging Spectrometer (MERIS) instrument on the Envisat satellite with a resolution of 1km pixel. A validation of the data was made by comparing MERIS data and in situ measurement available from ESO observatories in Chile, La Silla and Paranal, combined with lower resolution values from the GOES weather satellite. A detailed analysis of daytime cloud cover from 2002 to 2006 at four sites under study both in the northern and in the southern hemisphere for the E-ELT is presented.

Study on the spectral transmission characteristics of MWIR through the atmosphere

Abstract: This paper is a part of developing a software that predicts surface emitted radiance from ground objects by considering solar irradiation and atmospheric convection. The radiance emitted from a surface can be calculated by using the temperature and optical characteristics of the surface together with the spectral atmospheric transmittance. The thermal modeling is essential for identifying objects on the scenes obtained from the satellites. And the temperature distribution on the object is used to obtain their infrared images in contrast to the background. We considered the composite heat transfer modes including conduction, convection and spectral solar radiation for objects within a scene to calculate the surface temperature distribution. The software developed in this study could be used to model the thermal energy balance to obtain the temperature distribution over the object by considering the direct and diffuse solar irradiances and by assuming the conduction within the object as one-dimensional heat transfer into the depth. LOWTRAN7 are used to model the spectral solar radiation including the direct and diffuse solar energy components. The object considered is assumed to be consisted of several different materials with different properties, such as conductivity, absorptivity, density, and specific heat etc. Resulting spectral radiances in the MWIR region arrived at the sensor are shown to be strongly dependent on the spectral surface properties of the objects.

Accuracy assessments of standard products of ALOS optical instruments and their high level products

Abstract: This paper describes the updated results of calibration and validation for optical instruments onboard the Advanced Land Observing Satellite (ALOS, nicknamed "Daichi"), which was successfully launched on January 24th, 2006 and continuously works very well. ALOS has an L-band Synthetic Aperture Radar called PALSAR and two optical instruments i.e., the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2). PRISM consists of three panchromatic radiometers, and is used to derive a digital surface model (DSM) with high spatial resolution that is an objective of the ALOS mission. The geometric calibration is important in generating a precise DSM by stereo pair image of PRISM. AVNIR-2 has four radiometric bands from blue to near infrared and uses for regional environment and disaster monitoring etc . The radiometric calibration is also important for AVNIR-2 as well as PRISM. This paper describes updated results of the radiometric calibration of AVNIR-2, and geolocation determination accuracy evaluation as a part of geometric calibration, and validation of generated DSM by PRISM. These works will be done during the ALOS mission life as operational calibration to keep absolute accuracies of the standard products.

Empirical Storm-Time Correction to the International Reference Ionosphere Model E-Region Electron and Ion Density Parameterizations Using Observations from TIMED/SABER

Abstract: The response of the ionospheric E-region to solar-geomagnetic storms can be characterized using observations of infrared 4.3 micrometers emission. In particular, we utilize nighttime TIMED/SABER measurements of broadband 4.3 micrometers limb emission and derive a new data product, the NO+(v) volume emission rate, which is our primary observation-based quantity for developing an empirical storm-time correction the IRI E-region electron density. In this paper we describe our E-region proxy and outline our strategy for developing the empirical storm model. In our initial studies, we analyzed a six day storm period during the Halloween 2003 event. The results of this analysis are promising and suggest that the ap-index is a viable candidate to use as a magnetic driver for our model.