期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2007
卷号：XXXVI-7/C50
出版社：Copernicus Publications
摘要：provided by SPOT satellites or by wide field of view instruments (VGT, MERIS, MODIS),are degraded by two main geophysical sources of noise : 1) atmospheric effects, mainlybecause of aerosol scattering, difficult to correct because aerosol optical properties arehighly variable and difficult to characterise, and 2) directional effects, since the observedsurface reflectances depend on solar and observation angles.Since 2004, the Formosat2satellite, (and in the near future, the VENμS mission, seeDedieu et al, this conference) can provide very frequent high resolution images acquiredwith constant observation angles in the visible and near infrared. With these features,directional effects are considerably reduced, since only the solar angles vary slowly withtime. Furthermore, the quasi absence of surface directional effects allow to improveatmospheric corrections by determining the aerosol properties. For this, we use thefollowing properties:• aerosol optical properties vary quickly with time but slowly with location.• reflectances vary quickly with location but slowly with time, when there are nodirectional effects.In a few days period, if a variation of the top of atmosphere (TOA) reflectance occurs, it isvery likely to be due to variations of aerosol optical properties : it is thus possible toretrieve these properties from TOA reflectance variations. Such a method has been testedusing Formosat2time series over 3 sites : images are being acquired every third day fortwo sites in France, every fourth day for a site in Morocco, with constant observationangles. AERONET sun photometers as well as insitusurface reflectance measurementsare available on both sites.The method is providing quite good results for the optical thickness (standard deviationsare below 0.1) and the surface reflectance time series obtained after atmosphericcorrections are very smooth.
