def atmDensityPoly(ht, dens_co):
    """ Calculates the atmospheric density in kg/m^3. 
    
    Arguments:
        ht: [double] Height in meters.
        dens_co: [ndarray] Array of 7th order poly coeffs.
    Return:
        [double] Atmosphere density at height h (kg/m^3)
    """

    return 10**(dens_co[0] 
               + dens_co[1]*(ht/1e6) 
               + dens_co[2]*(ht/1e6)**2 
               + dens_co[3]*(ht/1e6)**3 
               + dens_co[4]*(ht/1e6)**4 
               + dens_co[5]*(ht/1e6)**5
               + dens_co[6]*(ht/1e6)**6
               )