When M is a compact
symmetric space, the spherical mean value operator Lr (for a fixed r > 0) acting on
L2(M) is considered. The eigenvalues λ for Lrf = λf are explicitly determined in
terms of the elementary spherical functions associated with the symmetric space.
Alternative proofs are also provided for some results of T. Sunada regarding the
special eigenvalues +1 and −1 using a purely harmonic analytic point of
view.