  The difference in the proper azimuthal periods of revolution of two standard
clocks in direct and retrograde orbits about a central rotating mass is
proportional to J/Mc^2, where J and M are, respectively, the proper angular
momentum and mass of the source. In connection with this gravitomagnetic clock
effect, we explore the possibility of using spaceborne standard clocks for
detecting the gravitomagnetic field of the Earth. It is shown that this
approach to the measurement of the gravitomagnetic field is, in a certain
sense, theoretically equivalent to the Gravity Probe-B concept.
