In preparation of the micro-bolometer based MIcro Satellite for Thermal Infrared GRound surface Imaging (MIST-IGRI) mission, we study the error budget of the Temperature-Emissivity Separation (TES) method using several spectral configurations that differ in channel numbers, locations, and widths. The error budget quantifies the contribution of (1) the TES underlying assumption about emissivity spectral contrast, (2) the errors on atmospheric corrections, and (3) the instrumental noise. When dealing with atmospheric corrections, we consider errors on atmospheric temperature, water vapor content, and concentrations of CO2 and O3. To that end, we design an end-to-end simulator of MISTIGRI measurements in order to simulate the radiative and biophysical quantities involved in the data processing. We conduct numerous simulations over a wide range of realistic setups that include cavity effect, i.e., radiance trapping within vegetation canopy. In the case of micro-bolometer based sensing, the current study highlights that atmospheric and instrumental noises have similar impacts on the TES retrievals, with resulting errors twice as large as those due to the TES intrinsic assumption about spectral contrast, where the latter contributes to the TES error budget within the [0.005-0.009] interval for emissivity, and within the [0.3 K-0.4 K] interval for LST. Also, we show that retrieval performances of surface temperature are very similar across all considered MISTIGRI spectral configurations, with RMSE variation within 0.2 K.< Réduire