I want to find pm10 concentration in large area so using ground station is not useful; so decide to use the relation between AOT and pm10 to found pm10 concentration and I use this formula from article

Estimation of PM10 Concentration using Ground Measurements and Landsat 8 OLI Satellite Image

Salah Abdul Hameed Saleh1 and Ghada Hasan

AOT(λ)= ao Rλ1 +a 1 Rλ2 + a2 Rλ3 + a3 Rλ4

Where Rλ is the atmospheric reflectance (i =1,2,3... Corresponding

to wavelength for satellite), and aj is the algorithm coefficient

(j =0,1,2,...) is empirically determined.

So how to determine ai value which is empirically determined?

What is the atmospheric reflectance for every band?

Pm10= ao Rλ1 +a 1 Rλ2 + a2 Rλ3 + a3 Rλ4

Where Rλi is the atmospheric reflectance (i =1,2,3,4.. corresponding

to satellite bands), and aj is the algorithm coefficient (j =0,1,2,3 ....) are

empirically determined.

So how to determine the atmospheric reflectance for every band and the ai value which is empirically determined?