This is the first in a series of two papers concerned with new accurate high resolution spectroscopic measurements of line positions and intensities of ozone in the 5 µm and 10 µm regions using a commercial Michelson Fourier transform spectrometer. Measurements in both wavelength regions have been made quasi simultaneously using a special H-shaped absorption cell with two parallel absorption paths of different length that remained connected during the experiments. Accurate ozone partial pressures were monitored on the shorter of the two paths using UV absorption at the 253.65 nm Hg reference line. In this paper, we report in detail on the experimental setup and provide a comprehensive uncertainty analysis. The spectral analysis and retrieved line parameters are provided in the second paper, which also contains the comparison to the literature data. Line positions have been measured with standard uncertainties of u(ν 0) = 3 • 10 −5 cm-1 in both spectral regions, mainly in the ν 3 and the ν 1 + ν 3 bands of ozone. Intensities of most of the transitions in the ν 3 band have a relative standard uncertainty of u r (S) = 1.1 • 10 −2. The uncertainty is slightly smaller for intensities in the ν 1 + ν 3 band at 5 µm. The highly accurate experimental data provide a benchmark for molecular calculations and the 1.1% line intensity uncertainty will help resolving the discrepancy between UV and IR atmospheric ozone retrievals and correcting current biases in spectroscopic databases.