  We consider the production process e-e+ -> G\gamma of invisible gravitons (G)
at future linear colliders. We discuss whether the angular distribution of the
photon (\gamma) can be used to measure the spin of the invisible graviton, or
of any other invisible objects produced. We propose a method based on the
Fourier expansion of the transverse energy squared moment distribution of the
photon. We provide justification for this method, and confirm, especially for
the case of two extra dimensions, that the method is valid within a realistic
setup, which includes the simulation of the Standard Model background,
beamstrahlung, bremsstrahlung, calorimeter resolution and calorimeter coverage.
When the number of extra dimensions is increased, the angular distribution does
not provide sufficient information to extract the spin, but this method still
offers a useful parameterization of the single photon cross section using which
the nature of the missing object can be studied.
