A hollow-waveguide gas correlation radiometer for ultra-precise column measurements of formaldehyde on Mars

We present preliminary results in the development of a miniaturized gas correlation radiometer that implements a hollow-core optical fiber (hollow-waveguide) gas correlation cell. The substantial reduction in mass and volume of the gas correlation cell makes this technology appropriate for an orbital mission?capable of pinpointing sources of trace gases in the Martian atmosphere. Here, we demonstrate a formaldehyde (H2CO) sensor and report a detection limit equivalent to ~30 ppb in the Martian atmosphere. The relative simplicity of the technique allows it to be expanded to measure a range of atmospheric trace gases of interest on Mars such as methane (CH4), water vapor (H2O), deuterated water vapor (HDO), and methanol (CH3OH). Performance of a formaldehyde instrument in a Mars orbit has been simulated assuming a 3 m long, 1000 ?m inner diameter hollow-core fiber gas correlation cell, a 92.8? sun-synchronous orbit from 400 km with a horizontal sampling scale of 10 km ? 10 km. Initial results indicate that for 1 s of averaging, a detection limit of 1 ppb is possible.