[GRASSLIST:7425] Re: Convert DN's to reflection

[Hamish]

> I now want to convert  radiance values are at-the-top-of-the
> atmosphere to measures of reflectance using
> 
> rhop = (pi * L * d2)/(ESUN * cos(thetas))
> where L is the measured TOA radiance, d is the earth-sun
> distance in astronomical units, and thetas is the solar zenith
> angle
> 
> I was unsure of what L should be in this case. Also could
> someone help me see the light with the concept of Julian Days,
> so that I can get the value of d. The data is from November
> 22, 1988.


Julian days is just 1-365. So Nov 22 is Julian day 326. (1988 was not a
leap year)


Getting from d to AU is up to you & Google...



Hamish