The Gravitomagnetic measurement of the angular momentum of celestial   bodies
  The asymmetry in the time delay for light rays propagating on opposite sides of a spinning body is analyzed. A frequency shift in the perceived signals is found. A practical procedure is proposed for evidencing the asymmetry, allowing for a measurement of the specific angular momentum of the rotating mass. Orders of magnitude are discussed. 
Angelo Tartaglia, Matteo Luca Ruggiero