A description of a resonance line Feautrier radiative transfer (RT) code which allows for coupling between closely spaced emission lines is presented. This code has been used to model closely spaced H and D Lyman α 1215.67 ¿ and 1215.34 ¿ emission lines, respectively, in the Jovian thermosphere. There is no direct interaction between these lines, but coupling and energy transfer may occur as the Voigt broadened lines overlap. The RT method is pseudo three-dimensional in that a spherical shell atmosphere is accounted for in direct solar beam scattering but with one-dimensional (1-D) plane-parallel multiple scattering. In addition, allowance is made for a varying solar zenith angle along the line of sight in calculating intensities. Using a model atmosphere for thermospheric D and H produced by a 1-D photochemical-diffusion model, we present results illustrating the relative importance of including coupling of H and D Lyman α emission lines in radiative transfer calculations for both the disk and limb of Jupiter. These results suggest that the spectral contrast between the H and D Lyman α features is reduced in long limb path geometries and that the disk measurement provides better detection possibilities. ¿ 2000 American Geophysical Union