MODIS NDVI optimization to fit the AVHRR data series spectral considerations

In early 1999 about when this article win hit the press. NASA is scheduled to launch its first Earth Observing satellite System (EOS) with array of instructions for precise, scientific, remote sensing of the Earth land ocean, and atmospheres. One of the main instruments, MODIS, will monitor daily vegetation dynamics with seven specially selected and highly characterized and calibrated spectral channels in the solar spectrum, with spatial resolution from 250 m to 500 m. These MODIS data, together with multiangular observations from the MISR instrument (also on EOS), will generate a much better picture of vegetation dynamic than previous satellite data records. But studying changes on, the Earth surface takes years and decades. To do it in our scientific lifetime, there is a need to be able to develop a data series that combines the traditional NDVI-AVHRR data sets that was used to monitor vegetation dynamics with the new MODIS data with its narrower channels. Here we propose that due to spectral differences between the AVHRR and MODIS, a combination of the MODIS red and green channels should be used to represent the AVHRR red channel in such long term data series, to avoid a step in the NDVI of delta NDVI of up to 0.05. We use both leaf spectra and full canopy spectra to develop and test this optimization. Optimization of the MODIS sensitivity for monitoring the dynamics of vegetation chlorophyll content is also discussed. (C) Elsevier Science Inc., 1998.