TUNABLE DIODE-LASER IR SPECTROMETER FOR INSITU MEASUREMENTS OF THE GAS-PHASE COMPOSITION AND PARTICLE-SIZE DISTRIBUTION OF TITANS ATMOSPHERE

A new instrument, the Probe Infrared Laser Spectrometer (PIRLS), is described for in situ sensing of the gas composition and particle size distribution of Titan’s atmosphere on the NASA/ESA Saturn OrbiterATitan Probe Cassini Mission. For gas composition measurements, several narrow bandwidth (0.0001 cm-2) tunable lead-salt diode lasers operating near 80 K at selected, mid-IR wavelengths (3-16 μm) are directed over a pathlength defined by a small reflector extending over the edge of the probe spacecraft platform; volvune mixing ratios of 10-2 should be measurable for several species of interest. A cloud particle size spectrometer using a diode laser source at 0.78 μm shares the optical path and deployed reflector; a combination of imaging and light scattering techniques will be used to determine sizes of haze and cloud particles and their number density as a function of altitude. Key words: Tunable diode laser; infrared laser spectrometer; Titan; insitu high resolution laser spectroscopy. © 1990 Optical Society of America.