We are planning a mission to Mars using a micro-satellite to carry a sub-millimeter sensor to orbit and have performed a feasibility study to determine what we can measure and to what success. The sensor will measure atmospheric molecular oxygen, water, ozone, and hydrogen peroxide to retrieve their volume mixing ratios and change over time. The sensor will also retrieve the temperature field, the wind field, and the magnetic field at various levels of success. The expected measurement errors for molecular oxygen is below 100 ppmv in limb view below 50 km, with 20 ppmv for near surface measurements. For water in limb-view, the retrieval errors are below 1 ppmv with a detection limit of a few tens of ppbv. For ozone the limits are at 2 ppbv, and for hydrogen peroxide the retrieval limits are in the range of 1 ppbv. In nadir-viewing geometry, the expected errors in the column are worse but not by much since we can keep integrating the signal from the same area for a long time, though the vertical resolution clearly suffers.