Non-LTE (local thermal equilibrium) calculated vibrational temperatures of CO2 and N2 in the altitude z region 40140 km are presented in this paper. Improvements in these calculations over those we have reported previously include (1) improved rate constants, (2) a detailed radiative transport treatment for the vv2 modes of CO2, (3) th use of the most recently determined efficiency (33%) for the excitation of N2≠ via O(1D)+N2→3P+N2≠, (4) the radiation transport in the weak CO2v3 bands, and finally, (5) a better selection of altitude mesh points in order to achieve numerically more accurate solutions and to extend the lower boundary of the calculations zL from 50 down to 40 km. The improved calculation for Tn2 and T001 are in good general agreement with our previous publications. The change in the efficiency for excitation of N2≠ by quenching O(1D) made the most noticeable change in our most recent calculations: absorption of 4.3-&mgr;m sunlight in the weak bands also impacted these calculations significantly. The v1v2 calculations provide a decent fit to 15-&mgr;m zenith radiance data for altitudes z≲95 km. At higher altitudes it will be necessary to account for thermal line and band broadening in order to achieve a better fit to the data. The thermal broadening increases rapidly as a function of increasing altitude in the lower thermosphere. With the exception of the fluorescent bands the qualitative behavior of the weak CO2v3 band upper state vibrational temperatures Tv3j relative to Tn2 and T001 may be understood on the basis of the relative efficiency of these bands for radiation to space in comparison with the efficiency of the optically thicker, strong v3 band, the 12C1u8O2 (or 626) 001-000 fundamental. These weak bands contribute much more than the fundamental to 4.3-&mgr;m zenith radiance in the altitude range z≲70 km. With regard to the 4.3-&mgr;m earth limb the nonfluorescent weak bands can be expected to contribute more than the fundamental for z≲85 km, but the CO22.7-to4.3-&mgr;m fluorescence of sunlight will still dominate the non-LTE 4.3-&mgr;m earth limb below 95 km. Resolved measurements of zenith or earth limb below 95 km. Resolved measurements of zenith or earth limb radiance in the fluorescent bands may be used to obtain information on the extent to which the upper levels of the hot 15-&mgr;m bands 10¿0, 02¿0, and 02¿0 are in LTE among themselves in the mesosphere and lower thermosphere. This information would be useful for understanding non-LTE atmospheric radiative cooling near 15 &mgr;m.