NanoCarb is an innovative Fourier-transform imaging spectrometer dedicated to the measurement of CO 2 and CH 4. Both its unusual optical principle and sampling strategy allow to reach a compact design, ideal for small satellite constellation as investigated by the European project SCARBO. The NanoCarb performance assessment as well as a proof of concept is required in this framework. We have developed a design strategy to optimize the performances. We demonstrate the potential of the concept through an estimation of the sensitivity, compliant with the space mission target. We also present a preliminary mitigation of the bias induced by water on CO 2 and CH 4 retrieval, illustrating the efficiency and the flexibility of the NanoCarb partial interferogram sampling technique. The presented design reaches a sub-ppm random error for CO 2 and sub-10 ppb random error for CH 4 , considering 128 km swath and 2 by 2 km 2 ground resolution. Design optimization and more systematic performances are discussed.