An AOTF-LDTOF Spectrometer Suite for In Situ Organic Detection and Characterization

We discuss the development of a miniature near-infrared point spectrometer, operating in the 2-4 micron region, based on acousto-optic tunable filter (AOTF) technology. This instrument may be used to screen and corroborate analyses of samples containing organic biomarkers or mineralogical signatures suggestive of extant or extinct organic material collected in situ from planetary surfaces. AOTF technology has the potential to enable significant near-IR spectroscopic diagnostic capability without exceeding the resources of a small surface laboratory. An optically bright, broadband emitter and AOTF combination is used as a tunable narrowband light source, the light from which is guided to a small (~0.04 cm^2) sample area using large (600 micron) diameter infrared fibers. AOTFs have been demonstrated to be rugged and radiation-hard devices, but their principal advantage is rapid wavelength change and the ability to sample at arbitrarily chosen wavelengths, which maximizes information content. Spectrum acquisition is performed using a sensitive point detector. Samples with evidence of organics or other species of astrobiological interest may be further analyzed using a co-focused time-of-flight mass spectrometer (TOF-MS), using laser desorption (LD) to sample and ionize complex molecules directly from the sample surface. The combined instrument geometry allows the LDTOF to quickly verify and identify any reduced organics detected in the rapid AOTF survey of the identical sample. The combination of an AOTF IR point spectrometer with LDTOF thus provides a very practical and efficient astrobiology investigation that is compact and rugged enough for a lander platform targeted for Mars, an asteroid, or icy moons of the outer solar system. This work is supported by NASA's ASTID and EPSCoR programs through grant numbers NNX08AY44G and NNX08AV85A, respectively.