The well-being of the crew on manned missions depends critical on the composition of the habitat air. Oxygen, carbon dioxide and water vapor are the most important air constituents that have to be monitored continuously. Optical monitoring with its features of high precision, strong species selectivity and fast response is the preferred method if lightweight, small and low power-draw instrumentation can be developed. Vertical cavity surface emitting lasers (VCSELs) are now available covering a broad wavelength range. These single frequency light sources are ideal candidates for high performance gas monitoring and especially suited for space applications due to their small size and extremely low power consumption. Vista Photonics proposes to develop technology based on these lasers that leads to small sensors that fulfill the strict requirements of spaceflight. The narrowband output of these lasers combined with wavelength modulation spectroscopy and a compact absorption cell will provide superior sensor performance. Inherent features like sensor health monitoring and recalibration without the use of expendable gases will be incorporated. The developed sensor will be fully automated and no maintenance will be required.