Using new and accurate experimental results concerning the spectroscopic properties of the H14NO3 and H15NO3 molecules, as well as improved theoretical methods, it has been possible to generate an improved set of line parameters for these molecules in the 11.2 ¿m spectral region. These line parameters were used to detect for the first time the H15NO3 molecule in the atmosphere analyzing atmospheric spectra recorded by the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) experiment. The evidence of H15NO3 in the atmosphere was achieved exploiting the features of the Residual and Error Correlation analysis.