def model_musp(wavelength_in_nm, coeffs):
    """
    Parameter estimation for the scattering model used by 
    mcxyz as the DKFZ simulation framework uses this approximation

    Keyword arguments: [pysical units]
    wavelength_in_nm -- wavelengths in numpy array [/nm]
    coeffs[] -- for fitting, including: 
        0: musp500 -- reduced scattering coeff. at 500 nm [/cm]
        1: fray -- fraction of Rayleigh scattering at 500 nm
        2: bmie  -- scatter power for mie scattering
    """
    musp = coeffs[0]*(coeffs[1]*(wavelength_in_nm/500)**(-4) 
                    + (1 - coeffs[1])*(wavelength_in_nm/500)**(-coeffs[2]))
    return musp*100.