derived total precipitable water 1°x1° data products at 8:00 hrs 
IST and 14:00hrs IST were used for 7,10,17hrs. acquisitions and 
12,14hrs. acquisitions respectively. The average atmospheric 
turbidity parameters, & and ß, were used for all weather 
conditions. The sensitivity analysis showed the degree of 
dependence of total insolation on both the parameters. Thus the 
proper tuning of turbidity parameters according to changing 
weather conditions can increase the accuracy of insolation 
retrieval. 
4. CONCLUSIONS 
Although the present study showed the possibility of insolation 
retrieval using geostationary data over India for both clear and 
cloudy sky conditions, but its large area validation with more 
number of image acquisitions per day and huge real time ground 
based observations is the need of the hour. The cloud 
attenuation coefficients and turbidity parameters need to be fine 
tuned using real time pyranometer and sun photometer 
observations. The retrieval of precipitable water for 
atmospheric corrections in insolation retrieval scheme will be 
possible with the future launch of INSAT-3D having ‘Imager’ 
with six channels including two thermal bands. 
ACKNOWLEDGEMENTS 
We are highly thankful to EUMETSAT , Germany to provide 
us Meteosat-5 datasets for carrying out this study. We are 
grateful to Shri J. S Parihar, Group Director, Agricultural 
Resources Group and Director, RSAM, Space Applications 
Centre, Ahmedabad for constantly giving us encouragement. 
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