In the paper under review, the authors consider the extent to which the ortho spectrum (or orthogonal spectrum) of a hyperbolic surface with totally geodesic boundary determines the surface up to isometry. This is the analogue for the ortho spectrum of known results for the length spectrum, where it is known that there are closed hyperbolic surfaces that are isospectral (that is, have the same length spectrum) but which are not isometric. \par The authors show that a similar results holds for the ortho spectrum. Given its definition in terms of geodesic arcs between totally geodesic boundary components, the surface here is required to be compact with non-empty totally geodesic boundary. Specifically, the authors show in Theorem 6.3 that there are surfaces with the same ortho spectrum but different systolic lengths (where the systolic length is the minimum of the length spectrum) which hence cannot be isometric. The authors also show in Theorem 5.1 that for a fixed ortho spectrum, there are only finitely many hyperbolic structures on a given surface with that ortho spectrum. \par The authors provide a brief summary of results regarding isospectral but not isometric surfaces, which puts the results proven in this paper clearly in context. The proofs use both results regarding the hyperbolic geometry of pairs of pants and hyperbolic trigonometry, and also analysis of the properties of the critical exponent. The paper closes with a short discussion of the ortho exponent for hyperbolic 3-manifolds and its connection to known results about the circle packing exponent.