Synthetic HD (J = 1–0) spectra. Top: five-point cross sampled at ${15}_{.}^{\mathrm{\prime }\mathrm{\prime }}95$ distance, against the gray-shaded Jupiter disk. The vertical axis coincides with the planet’s sky-plane projected rotation axis. All spectra have the same ordinate range (in K on T_mb scale) and are continuum-subtracted for clarity. The white-hatched circle centered at offset (${15}_{.}^{\mathrm{\prime }\mathrm{\prime }}95$, $0_{.}^{\mathrm{\prime }\mathrm{\prime }}0$) displays the half-power beam width of the observations. The systemic velocity is marked by vertical dotted lines. Bottom: differential spectrum between offsets ($+{15}_{.}^{\mathrm{\prime }\mathrm{\prime }}95,0_{.}^{\mathrm{\prime }\mathrm{\prime }}0$) and ($-{15}_{.}^{\mathrm{\prime }\mathrm{\prime }}95,0_{.}^{\mathrm{\prime }\mathrm{\prime }}0$) (red). The equivalent spectrum without pressure-induced line shift (gray) is shown for comparison.