Two satellites \( S_1 \) and \( S_2 \) are revolving in circular orbits around a planet with radius \( R_1 = 3200 \, \text{km} \) and \( R_2 = 800 \, \text{km} \) respectively. The ratio of speed of satellite \( S_1 \) to the speed of satellite \( S_2 \) in their respective orbits would be \( \frac{1}{x} \) where \( x = \) ______________.
