The MVACS tunable diode laser spectrometers

Two independent tunable diode laser spectrometers are resident aboard the M ars Polar Lander as part of the Mars Volatiles and Climate Surveyor payload . One spectrometer is located on the meteorological mast for measurements o f H2O and CO2 in the free atmosphere, and the other serves as the H2O and C O2 analyzer for the Thermal and Evolved Gas Analyzer. Water vapor is measur ed using a tunable diode laser operating at 1.37 Am, while CO2 is measured using a second laser operating near 2.05 mum. The 2.05 Am laser also has is otopic analysis capability. In addition to the major CO2 isotopomer ( (COO) -C-12-O-16-O-16), analyses of (COO)-C-13-O-16-O-16 and (COO)-C-12-O-18-O-16 in the atmosphere and in the Thermal and Evolved Gas Analyzer are possible under certain conditions. The spectrometers were designed and built at the Jet Propulsion Laboratory and have their heritage in a series of tunable d iode laser spectrometers developed for Earth atmospheric studies using high -altitude aircraft and balloon platforms. The 137 mum diode laser on the me teorological mast will provide the first in situ measurements of water vapo r in the Martian boundary layer, with a detection sensitivity an order of m agnitude greater than the water vapor abundances inferred from the remote-s ensing observations by the Viking Orbiters.