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1. Jan 18, 2016

### ecastro

I stumbled upon this equation for a Lambertian uniform target:

$\rho^{*} = \frac{\pi L}{\mu_s E_s}$,

where $\rho^{*}$ is the reflectance, $L$ is the measured radiance, $E_s$ is the solar flux at the top of the atmosphere, and $\mu_s$ is the cosine of the sun zenith angle, $\theta_s$.

The equation confuses me if I were to consider a monochromatic reflectance of the target, i.e. the reflectance of the target at a specific wavelength. What should be the measured reflectance for this case, is it the spectral radiance, should its units be $\frac{W}{m^2 nm^2 sr}$? How about the solar flux (I considered it to be equivalent to the irradiance of the source at the target), should it be spectral irradiance, which I can calculate by the black-body radiation equation?

2. Jan 23, 2016