The 2007 National Research Council (NRC) Decadal Survey on Earth Science and Applications from Space recommended Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) as a mid-term, Tier II, NASA space mission. ITT Exelis, formerly ITT Corp., and NASA Langley Research Center have been working together since 2004 to develop and demonstrate a prototype Laser Absorption Spectrometer for making high-precision, column CO2 mixing ratio measurements needed for the ASCENDS mission. This instrument, called the Multifunctional Fiber Laser Lidar (MFLL), operates in an intensity-modulated, continuous-wave mode in the 1.57- micron CO2 absorption band. Flight experiments have been conducted with the MFLL on a Lear-25, UC-12, and DC-8 aircraft over a variety of different surfaces and under a wide range of atmospheric conditions. Very high-precision CO2 column measurements resulting from high signal-to-noise (great than 1300) column optical depth measurements for a 10-s (approximately 1 km) averaging interval have been achieved. In situ measurements of atmospheric CO2 profiles were used to derive the expected CO2 column values, and when compared to the MFLL measurements over desert and vegetated surfaces, the MFLL measurements were found to agree with the in situ-derived CO2 columns to within an average of 0.17% or approximately 0.65 ppmv with a standard deviation of 0.44% or approximately 1.7 ppmv. Initial results demonstrating ranging capability using a swept modulation technique are also presented.

/pdf/atmospheric-co2-column-measurements-with-an-airborne-2v8chyb49w.pdf

Atmospheric CO2 column measurements with an airborne intensity-modulated continuous wave 1.57 μm fiber laser lidar.

We employed a new experimental technique known as spatially resolved capillary-inlet mass spectrometry (SpaciMS) to observe the evolution of multiple species inside the channels of a monolithic NO x storage-reduction (NSR) catalyst. The NSR material consisted of a Pt/K/Al 2 O 3 washcoat deposited inside cordierite monolith channels. Spatially and temporally resolved measurements were made over the monolith length in a bench flow reactor during fast cycling between synthetic lean and rich environments at 200 and 300 °C. Regeneration was found to be very efficient at 300 °C regardless of whether pure H 2 , pure CO, or mixtures of H 2 and CO were employed. At 200 °C, CO was noticeably less effective than H 2 . We conjecture that at 200 °C CO may be inhibiting the regeneration process through its strong adsorption on Pt. Generation of H 2 by water-gas shift was seen at 300 °C but not at 200 °C.

Spatially resolved in situ measurements of transient species breakthrough during cyclic, low-temperature regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

A transient image is the optical impulse response of a scene which visualizes light propagation during an ultra-short time interval. In this paper we discover that the data captured by a multifrequency time-of-flight (ToF) camera is the Fourier transform of a transient image, and identify the sources of systematic error. Based on the discovery we propose a novel framework of frequency-domain transient imaging, as well as algorithms to remove systematic error. The whole process of our approach is of much lower computational cost, especially lower memory usage, than Heide et al.'s approach using the same device. We evaluate our approach on both synthetic and real-datasets.

/pdf/fourier-analysis-on-transient-imaging-with-a-multifrequency-5brb8ls9qw.pdf

Fourier Analysis on Transient Imaging with a Multifrequency Time-of-Flight Camera

Amplitude-modulated continuous wave (AMCW) time-of-flight (ToF) range imaging cameras measure distance by illuminating the scene with amplitude-modulated light and measuring the phase difference between the transmitted and reflected modulation envelope. This method of optical range measurement suffers from errors caused by multiple propagation paths, motion, phase wrapping, and nonideal amplitude modulation. In this paper a ToF camera is modified to operate in modes analogous to continuous wave (CW) and stepped frequency continuous wave (SFCW) lidar. In CW operation the velocity of objects can be measured. CW measurement of velocity was linear with true velocity (R2=0.9969). Qualitative analysis of a complex scene confirms that range measured by SFCW is resilient to errors caused by multiple propagation paths, phase wrapping, and nonideal amplitude modulation which plague AMCW operation. In viewing a complicated scene through a translucent sheet, quantitative comparison of AMCW with SFCW demonstrated a reduction in the median error from -1.3  m to -0.06  m with interquartile range of error reduced from 4.0 m to 0.18 m.

/pdf/application-of-lidar-techniques-to-time-of-flight-range-2pwrjqh6iq.pdf

Application of lidar techniques to time-of-flight range imaging

Effect of potassium and water vapor on the catalytic reaction of nitric oxide and dioxygen over platinum

A compact frequency-modulated, continuous wave (FM-cw) lidar system for measurement of distributed aerosol plumes and hard targets is presented. The system is based on intensity modulation of a laser diode and quadrature detection of the return signals. The advantages of using laser diode amplitude modulation and quadrature detection is a large reduction in the hardware required for processing and storing return signals as well as the availability of off-the-shelf integrated electronic components from the wireless and telecommunication communities. Equations to invert the quadrature signal components and determine spatial distributions of multiple targets are derived. Spatial scattering intensities are used to extract aerosol backscatter coefficients, which can then be directly compared to microphysics aerosol models for environmental measurements. Finally, results from laboratory measurements with a monostatic FM-cw lidar system with both hard targets and aerosols are discussed.

Intensity-modulated, stepped frequency cw lidar for distributed aerosol and hard target measurements

Lean phase operation of lean NOx adsorbers or lean NOx traps (LNTs) is analyzed using data from highly controlled isothermal bench-flow experiments on Pt/K/Al2O3 catalysts. Simulated diesel exhaust was used for inflow in the experiments. Pt promotes the oxidation of NO, the primary component of engine-out NOx, to NO2 which is more easily adsorbed and stored as KNO3. While the presence of Pt was found to be essential for capturing the NOx from the exhaust, it was seen that the NOx storage efficiency did not increase indefinitely with increasing Pt loading. Pt loading at a given temperature of operation is optimal when the rate of NO oxidation to NO2 is nearly equal to the NO2 adsorption rate at the sorbent sites. The NOx storage efficiency seems to be kinetically limited at lower temperatures and equilibrium limited at higher temperatures. When the lean/NOx capture operation was started from a fully regenerated condition, the NOx storage efficiency under most conditions was found to be independent of the reductant mixture used for regenerating the catalyst. The experiments also indicate the possibility of a significant NOx reduction reaction even under the highly oxidizing conditions. This reduction reaction seems to be of fractional order and is more significant at lower temperatures. More detailed analysis of the outflow from the reactor using Fourier-Transform-Infrared (FTIR) spectroscopy is being planned to identify the final product of this reduction reaction.

Phenomenology of NOx Adsorber Catalysts

Key Characteristrics of the Sorption Process in Lean Nox Traps

Nuclear Thermal Propulsion (NTP) systems are actively being developed for future crewed missions to Mars. NTP systems excel in missions where both high thrust and high specific impulse are required, but modern NTP systems currently do not have a Technology Readiness Level (TRL) high enough for use in crewed space exploration. TRLs are used to demonstrate the level of rigor with which a component/system has been tested/demonstrated for its intended use. While space systems technology in general must be qualified as a unit, nuclear technology must be first demonstrated to meet qualification level requirements both at the fuel (component) level and the reactor (subsystem) level. In this paper, historic NTP development programs are surveyed to identify a testing and development strategy that can be effectively implemented to allow for NTP reactor development. Based on this strategy, required facilities to enable such activities are identified. Current domestic experimental capabilities to support NTP qualification are limited to separate effects testing of individual components. Separate effects testing is found extensively in historic NTP development efforts but is not sufficient for full fuel and reactor qualification. Combined effects testing allows for an accurate assessment of fuel performance but is not achievable for NTP conditions in existing facilities. Assessment of historic development programs suggests that an intermediate, subscale test facility is necessary to advance NTP TRLs. A solution to meet this need is proposed, namely the Subscale Maturation of Advanced Reactor Technologies (SMART) facility. SMART will mitigate risk to NTP development by enabling performance and reactor physics demonstrations of NTP subsystems. A SMART facility could be built by modifying existing nuclear test facilities, which may potentially enable schedule and cost savings. To pursue reactor qualification beyond the subscale, a new ground test facility will be necessary. This ground test facility should be developed concurrently with SMART to allow for the facility to be operational in time for expedited NTP engine demonstration. 

Subscale maturation of advanced reactor technologies (SMART): A path forward for nuclear thermal propulsion fuel and reactor development

During this reporting period, the HFIR-MFE-RB-200J-1 spectrally tailored capsules were disassembled and the individual specimens recovered, sorted, and identified. Tensile testing and irradiation creep measurements will be performed during the next reporting period.

Status of DOE/JAERI collaborative program phase II and phase III capsules

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