The paper systematically investigates non-ideal instrumental effects (e.g., retroreflector misalignments, baseline drift, spectral channeling) in the Bruker FTS 120M spectrometer, employing diagnostic tools (ALIGN60, LINEFIT) for characterization and mitigation. This paper well highlights the importance of routine performance evaluations and maintenance schedules for long-term operational stability of FTIR measurements essential for atmospheric trace gas retrievals. While the research is technically sound and addresses a critical gap in NDACC/TCCON protocols, several issues require clarification and revision to enhance clarity, consistency, and scientific rigor.

• Figure 5 labels the x-axis in Hz (frequency domain), while Figure 15 uses cm⁻¹ (wavenumber domain) without justification. This inconsistency requires clarification or standardization.
• Figure 12 (temporal evolution of FTIR transmission spectra) is not cited or discussed in the main text, leaving its relevance unclear.
• The manuscript alternates between "Figure" (e.g., Section 4) and "Fig." (e.g., Section 2.2.1) for figure references. A uniform style should be adopted.
• The methodology for computing the ILS averaging kernel in Figure 16 is not described, including whether it derives from LINEFIT retrievals or ALIGN60 simulations.
• Channeling frequencies listed in Table 3 (e.g., 2.9750 cm⁻¹) are not explicitly mapped to the FFT peaks in Figure 15, creating ambiguity in their correlation.
• ‌Residuals in Figure 14 appear identical for "Nominal" (absolute values) and "Modified" (percentage), undermining direct comparison. Figure 13 similarly lacks clarity in residual scaling.
• ‌The cited RMS range (3.7×10⁻³ to 5.04×10⁻³) does not match the values displayed in Figure 14’s residual plots, necessitating verification.
• While ILS improvements are shown, there is minimal validation of how these translate to more accurate retrievals of key atmospheric trace gases (e.g., CO, C₂H₆). Concrete examples linking ILS metrics to retrieval errors would strengthen relevance.
• The paper lacks a detailed flowchart or step-by-step workflow for ALIGN60 and LINEFIT procedures. A visual schema would enhance reproducibility, especially for non-specialists.

Review provided in the attached pdf file.