Yoram Kaufman

Angular and seasonal variation of spectral surface reflectance ratios: implications for the remote sensing of aerosol over land

We obtain valuable information on the angular and seasonal variability of surface reflectance using a hand-held spectrometer from a light aircraft. The data is used to test a procedure that allows us to estimate visible surface reflectance from the longer wavelength 2.1 /spl mu/m channel (mid-IR). Estimating or avoiding surface reflectance in the visible is a vital first step in most algorithms that retrieve aerosol optical thickness over land targets. The data indicate that specular reflection found when viewing targets from the forward direction can severely corrupt the relationships between the visible and 2.1 /spl mu/m reflectance that were derived from nadir data. There is a month by month variation in the ratios between the visible and the mid-IR, weakly correlated to the Normalized Difference Vegetation Index (NDVI). If specular reflection is not avoided, the errors resulting from estimating surface reflectance from the mid-IR exceed the acceptable limit of /spl Delta//spl rho//spl sim/0.01 in roughly 40% of the cases, using the current algorithm. This is reduced to 25% of the cases if specular reflection is avoided.

The quality and significance of remote sensing of aerosol from EOS-Terra-MODIS instrument

The Terra mission will help quantify aerosol radiative forcing of climate by providing innovative measurements of the aerosol daily spatial distribution and identifying dust, smoke and regional pollution. MODIS aerosol information is being validated and supplemented by measurements bv the Aerosol Robotic Network (AERONET) of 100 global ground-based instruments. AERONET measures the aerosol spectral optical thickness and the total precipitable water vapor every 15 minutes throughout the day. These aerosol measurements should be very important as input to models that calculate radiative forcing and predict climate change.

Overview of EOS AM-1 platform and science

NASAs Earth Observing System is poised to launch the first major platform for Earth remote sensing, EOS AM-1. The platform, scheduled for launch in late 1998, will have five instruments and acquire global data for a wide variety of scientific studies of the Earths land, oceans, and atmosphere. This paper discusses the unique technological advances incorporated into the design of the platform. The key Earth System Science observations are highlighted along with the plans for science outreach activities.