Search results for "Radiometer"
showing 10 items of 272 documents
Interpolation and Gap Filling of Landsat Reflectance Time Series
2018
Products derived from a single multispectral sensor are hampered by a limited spatial, spectral or temporal resolutions. Image fusion in general and downscaling/blending in particular allow to combine different multiresolution datasets. We present here an optimal interpolation approach to generate smoothed and gap-free time series of Landsat reflectance data. We fuse MODIS (moderate-resolution imaging spectroradiometer) and Landsat data globally using the Google Earth Engine (GEE) platform. The optimal interpolator exploits GEE ability to ingest large amounts of data (Landsat climatologies) and uses simple linear operations that scale easily in the cloud. The approach shows very good result…
On-line tools for microscopic and macroscopic monitoring of microwave processing
2007
International audience; Direct monitoring of temperature, chemistry and microstructure is required to understand microwave heating in more detail, in order to fully exploit the unique features this non-equilibrium processing method can offer. In this paper, we show first that microwave radiometry can be used to follow volumetrically the thermal trajectory of microwave-heated aluminium powder. In-situ Raman spectroscopy is then shown to evidence thermal gradients between diamond and silicon grains in a binary powder mixture. Finally, perspectives and preliminary results of microstructural analysis obtained from X-ray microtomography are presented.
Land Surface Temperature
2019
Abstract An introduction to the chapter on Land Surface Temperature (LST). The basic thermal infrared theory is presented with example algorithms for the retrieval of LST and emissivity data are described in the later section. Various methods to validate satellite Land Surface Temperature (LST) products exist, but the most accurate and conclusive method is the direct comparison against in situ LST obtained from spatially representative radiance measurements over homogeneous sites. Some validation results and insights found in the literature are provided and the determination of in situ emissivity and LST with thermal infrared field radiometers is explained. The chapter concludes with an exa…
Study of the diurnal cycle of stressed vegetation for the improvement of fluorescence remote sensing
2006
Chlorophyll fluorescence (Chf) emission allows estimating the photosynthetic activity of vegetation - a key parameter for the carbon cycle models - in a quite direct way. However, measuring Chf is difficult because it represents a small fraction of the radiance to be measured by the sensor. This paper analyzes the relationship between the solar induced Chf emission and the photosynthetically active radiation (PAR) in plants under water stress condition. The solar induced fluorescence emission is measured at leaf level by means of three different methodologies. Firstly, an active modulated light fluorometer gives the relative fluorescence yield. Secondly, a quantitative measurement of the Ch…
Sensitivity analysis of the fraunhofer line discrimination method for the measurement of chlorophyll fluorescence using a field spectroradiometer
2007
The Fraunhofer Line Discrimination (FLD) principle is established as a good method for remote sensing of solar induced chlorophyll fluorescence. Some improvements to the method are analysed in order to determine and reduce the sources of error in the estimation of the fluorescence emission. A sensitivity analysis has been performed over simulated data generated from real diurnal cycle measurements.
A preliminary assessment of a detailed two stream short-wave narrow-band model using spectral radiation measurements
1997
Abstract A data bank of measurements of global, direct and diffuse solar spectral irradiances at ground level for clear skies has been compiled for Valencia (Spain) dating back to December 1992. The measurements were made with a commercial Li-cor 1800 spectroradiometer with a range of 300–1100 nm and a spectral resolution of 6 nm. A preliminary comparative assessment has been carried out between the experimental data and model data. The chosen model was a detailed narrow-band model (208 spectral intervals from 0.2 to 4 μm) developed at the “Laboratoire d'Optique Atmospherique (LOA)” of the University of Lille (France). This plane-parallel multilayer model uses a two-flux method to solve the…
Estimating the difference between brightness and surface temperatures for a vegetal canopy
1995
Abstract The difference between the surface temperature T S and the brightness temperature T b , which can be measured with a thermal infrared radiometer, has been calculated for different surface emissivity values and different atmospheric conditions. These calculations show that T s − T b is often significant even for high surface emissivities and that the spectral band in which the measurements are performed is a key factor in the interpretation of T s − T b . In particular, it is not a simple matter to use the characterisation of the whole spectrum atmospheric radiation to derive T s from T b when the measurements are performed in the 8–14 μm atmospheric window.
Surface temperature and water vapour retrieval from MODIS data
2003
This paper gives operational algorithms for retrieving sea (SST), land surface temperature (LST) and total atmospheric water vapour content (W) using Moderate Resolution Imaging Spectroradiometer (MODIS) data. To this end, the MODTRAN 3.5 radiative transfer program was used to predict radiances for MODIS channels 31, 32, 2, 17, 18 and 19. To analyse atmospheric effects, a simulation with a set of radiosonde observations was used to cover the variability of surface temperature and water vapour concentration on a worldwide scale. These simulated data were split into two sets (DB1 and DB2), the first one (DB1) was used to fit the coefficients of the algorithms, while the second one (DB2) was u…
Theoretical split-window algorithms for determining the actual surface temperature
1993
Two split-window strategies for obtaining the actual surface temperature (AST) from an infra-red sensor system are investigated by means of simulations of radiometer signals for a wide range of different geophysical situations. The differences between strategies are closely related to the strong or weak presence of atmospheric effects in the split-window coefficient. It has been demonstrated that the strong presence makes it necessary to know the total atmospheric water vapour as well as the effective emissivities in the two thermal channels for applying the strong split-window method, whereas for the weak presence one only needs to know the emissivities. Simplified algorithms have been obt…
Multi-channel and multi-angle algorithms for estimating sea and land surface temperature with ATSR data
1996
Abstract A study has been carried out using LOWTRAN-7 simulations of the Along-Track Scanning Radiometer (ATSR) data at 11 and 12 μm wavelengths to compare the merits of the multi-angle technique with those of the currently used multi-channel technique (split-window method) to retrieve both sea surface temperature (SST) and land surface temperature (LST). To this end a simple single-channel double-angle viewing model is presented, which relates actual surface temperature to the two brightness temperatures measured from space in the two views of interest (ATSR nadir and forward). Subsequently, statistical retrieval coefficients for the double angle and split-window techniques are derived via…