Yttrium Iron Garnet (YIG) is a material with extremely wide ranging applications. It is a ferrimagnetic spinel with the narrowest ferromagnetic resonance linewidth of any known material. Despite decades of experiments on this material, data relating to its full magnon spectrum is sparse. The spectrum is known to contain 20 branches, but the most thorough work to date relies upon a 3-parameter hamiltonian derived from fitting just 3 (the only 3 that were observed in what is still the only INS measurement on this material). Increasing interest in YIG for applications in magnonics (the magnon equivalent of electronics) necessitates a direct measurement of the optical magnon modes, which are crucial for understanding and exploiting this material. We propose to take advantage of large single crystals that are commercially available and thoroughly map the entire excitation spectrum.