We propose to measure crystal field transitions of Co ions in Ba3CoSb2O9, proposed to be a unique experimental realization of the S=1/2 antiferromagnet on the triangular lattice, a theoretically much-studied frustrated model system with unusual physics such as classical spin liquid (Ising limit) or anomalous soft modes (rotons) in the Heisenberg limit, effects that have remained experimentally unexplored as available materials up to now have had spatially-distorted triangular-lattices or significant site disorder. We have 20g Ba3CoSb2O9 with hexagonal (3-fold) symmetry and no site mixing. We will probe transitions of the Kramers Co2+ ions in the trigonal crystal-field + spin-orbit coupling, determine the spin-orbital character of the ground state doublet and infer the extent of Ising-like anisotropy to complement proposed OSIRIS measurements on the low-energy spin dynamics.