The miniaturization of space systems push for cheaper and more compact instruments. The use of photonic crystals as optical filters are a promising option for the miniaturization of spectrometers. This thesis is part of a project in SRON where a novel concept using photonic crystals is being investigated for Earth observation. Ways of using the transmission of photonic crystals for remote sensing of methane were explored. Later, the effects of the concentrations of other gases and the reflectance of the surface in the performance of the instrument were investigated. A method of selecting which photonic crystals to use in the instrument was developed and used to improve its performance. Finally, an optical design was made to estimate the volume of such an instrument.