We have designed and built a miniature near-IR tunable diode laser (TDL) spectrometer for measuring <i>in situ</i> the water vapor mixing ratio either in the Martian atmosphere or thermally evolved from Martian soil or ice samples. The laser hygrometer uses a thermoelectrically cooled single-mode distributed-feedback TDL at 1.87 μm to scan over a selected vibration-rotation line of both H<sub>2</sub>O and CO<sub>2</sub> near 5327.3 cm<sup>−1</sup>. A working prototype that weighs only 230 g has been built and used to generate spectra whose analysis demonstrates precision sensitivities as fine as 1 part in 10<sup>6</sup> by volume in 1 s or 0.1 part in 10<sup>6</sup> in 10 s at Martian pressures and temperatures. Absolute uncertainties of ~5% are calculated.
© 2004 Optical Society of America
(010.7340) Atmospheric and oceanic optics : Water
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(300.6260) Spectroscopy : Spectroscopy, diode lasers
Christopher R. Webster, Gregory J. Flesch, Kamjou Mansour, Robert Haberle, and Jill Bauman, "Mars Laser Hygrometer," Appl. Opt. 43, 4436-4445 (2004)