A method for measuring a characteristic variable of a radiation source and/or of a medium crossed by the radiation between the source and an interferometer, the interferometer being adapted to plot an interferogram of the radiation by creating a finite number of optical path differences between two rays having followed the same path between the source and the interferometer, the method comprising: - an interferometric inversion carried out on the basis of the interferogram, so as to obtain a measurement of the characteristic variable, the method being characterized in that it comprises the steps consisting in: - estimating the contribution of each path difference to the interferometric inversion step, using a modeling by a radiative transfer code; - carrying out a selection from the path differences, without any sampling regularity constraints, according to the results of the estimation step, the realization of the selection comprising the use of an amount characterizing the performance or the improvement of the interferometric inversion, and the iterative repetition of the following steps: a: initially, no path difference is selected; b: calculating for each path difference the increase in the amount characterizing the performance or the improvement of the interferometric inversion, when adding said path difference to all of the previously selected path differences, this calculation involving the Jacobians of the interferogram, that is to say the partial derivatives of the signal of the interferogram relative to the amount(s) to be inverted; c: adding the path difference, that optimizes said amount, to all of the selected path differences, and repeating step b, until reaching a maximum number of selected path differences or until said amount exceeds a predetermined threshold; - plotting the interferogram using only the selected path differences, and - measuring the characteristic variable of the radiation source and/or of the crossed medium according to the information contained in the interferogram plotted using only the selected path differences, without reconstructing a spectrum of the sampled radiation from the interferogram. - an interferometric inversion carried out on the basis of the interferogram, so as to obtain a measurement of the characteristic variable, - estimating the contribution of each path difference to the interferometric inversion step, using a modeling by a radiative transfer code; - carrying out a selection from the path differences, without any sampling regularity constraints, according to the results of the estimation step, the realization of the selection comprising the use of an amount characterizing the performance or the improvement of the interferometric inversion, and the iterative repetition of the following steps: a: initially, no path difference is selected; b: calculating for each path difference the increase in the amount characterizing the performance or the improvement of the interferometric inversion, when adding said path difference to all of the previously selected path differences, this calculation involving the Jacobians of the interferogram, that is to say the partial derivatives of the signal of the interferogram relative to the amount(s) to be inverted; c: adding the path difference, that optimizes said amount, to all of the selected path differences, and repeating step b, until reaching a maximum number of selected path differences or until said amount exceeds a predetermined threshold; a: initially, no path difference is selected; b: calculating for each path difference the increase in the amount characterizing the performance or the improvement of the interferometric inversion, when adding said path difference to all of the previously selected path differences, this calculation involving the Jacobians of the interferogram, that is to say the partial derivatives of the signal of the interferogram relative to the amount(s) to be inverted; c: adding the path difference, that optimizes said amount, to all of the selected path differences, and repeating step b, until reaching a maximum number of selected path differences or until said amount exceeds a predetermined threshold; - plotting the interferogram using only the selected path differences, and - measuring the characteristic variable of the radiation source and/or of the crossed medium according to the information contained in the interferogram plotted using only the selected path differences, without reconstructing a spectrum of the sampled radiation from the interferogram.