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Detailed spectroscopic analysis of hydroxyl fundamental vibration‐rotation and pure rotation emission lines has yielded OH(υ,N) absolute column densities for nighttime earthlimb spectra in the 20 to 110‐km tangent height region. High‐resolution spectra were obtained in the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS 1A) experiment. Rotationally thermalized populations in υ = 1–9 have been derived from the fundamental bands between 2000 and 4000 cm−1. Highly rotationally excited populations with N ≤ 33 ( ≤ 2.3 eV rotational energy) have been inferred from the pure rotation spectra between 400 and 1000 cm−1. These emissions originate in the airglow region near 85–90 km altitude. Spectral fits of the pure rotation lines imply equal populations in the spinrotation states F1 and F2 but a ratio Π(A′):Π(A″) = 1.8±0.3 for the Λ‐doublet populations. A forward predicting, first‐principles kinetic model has been developed for the resultant OH(υ,N) limb column densities. The kinetic model incorporates a necessary and sufficient number of processes known to generate and quench OH(υ,N) in the mesopause region and includes recently calculated vibration‐rotation Einstein coefficients for the high‐N levels. The model reproduces both the thermal and the highly rotationally excited OH(υ,N) column densities. The tangent height dependence of the rotationally excited OH(υ,N) column densities is consistent with two possible formation mechanisms: (1) transfer of vibrational to rotational energy induced by collisions with O atoms or (2) direct chemical production via H + O3 → OH(υ,N) + O2.

The Miniature Radio Frequency (Mini-RF) system is manifested on the Lunar Reconnaissance Orbiter (LRO) as a technology demonstration and an extended mission science instrument. Mini-RF represents a significant step forward in spaceborne RF technology and architecture. It combines synthetic aperture radar (SAR) at two wavelengths (S-band and X-band) and two resolutions (150 m and 30 m) with interferometric and communications functionality in one lightweight (16 kg) package. Previous radar observations (Earth-based, and one bistatic data set from Clementine) of the permanently shadowed regions of the lunar poles seem to indicate areas of high circular polarization ratio (CPR) consistent with volume scattering from volatile deposits (e.g. water ice) buried at shallow (0.1-1 m) depth, but only at unfavorable viewing geometries, and with inconclusive results. The LRO Mini-RF utilizes new wideband hybrid polarization architecture to measure the Stokes parameters of the reflected signal. These data will help to differentiate "true" volumetric ice reflections from "false" returns due to angular surface regolith. Additional lunar science investigations (e.g. pyroclastic deposit characterization) will also be attempted during the LRO extended mission. LRO's lunar operations will be contemporaneous with India's Chandrayaan-1, which carries the Forerunner Mini-SAR (S-band wavelength and 150-m resolution), and bistatic radar (S-Band) measurements may be possible. On orbit calibration, procedures for LRO

Three-body rate coefficients for reactions of H + 0 2 + M where M = Nz and HzO have been measured in a high-temperature flow reactor as a function of temperature up to 750 K. Room-temperature rate coefficients for M = Ar have also been quantified. The rate coefficients are measured by the flash photolysis method where atomic hydrogen is produced by excimer laser photolysis of precursor molecules (HzS or HzO) and then probed by either laser-induced fluorescence or resonance absorption. The rate coefficient measurements for nitrogen (298-580 K) can be described by the Arrhenius expression exp[(825 f 130)/T] cm6 molecuk2 s-l. Rate coefficients measured for water are k~~o ( S 7 5 ) = (1.2 f 0.3) X k~,o(650) = (1.0 f 0.3) X 10-31, and k~~o ( 7 5 0 ) = (1.22;) X cm6 molecule-2 s-'. Room-temperature measurements for Ar gave a rate coefficient of kk(298) = (2.1 f 0.2) X 10-32.= (2.9 f 0.8) X

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energy barrier, the reaction coordinate of (1) involves a quantummechanical, temperature independent frequency; and with this model the low pre-exponential factor and negative activation energy of reaction(1) can be explained.