Evaluation of 2-m Pulsed Integrated Path Differential Absorption Lidar for Carbon Dioxide Measurement-Technology Developments, Measurements, and Path to Space.

The societal benefits of understanding climate change through the identification of global carbon dioxide sources and sinks led to the recommendation for NASA's Active Sensing of Carbon Dioxide Emissions over Nights, Days, and Seasons space-based mission for global carbon dioxide measurements. For more than 15 years, the NASA Langley Research Center has developed several carbon dioxide active remote sensors using the differential absorption lidar technique operating at 2-m wavelength. Recently, an airborne double-pulsed integrated path differential absorption lidar was developed, tested, and validated for atmospheric carbon dioxide measurement.

Feasibility study of a space-based high pulse energy 2 μm CO IPDA lidar.

Sustained high-quality column carbon dioxide (CO) atmospheric measurements from space are required to improve estimates of regional and continental-scale sources and sinks of CO. Modeling of a space-based 2 μm, high pulse energy, triple-pulse, direct detection integrated path differential absorption (IPDA) lidar was conducted to demonstrate CO measurement capability and to evaluate random and systematic errors. Parameters based on recent technology developments in the 2 μm laser and state-of-the-art HgCdTe (MCT) electron-initiated avalanche photodiode (e-APD) detection system were incorporated in this model.

Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO strong absorption line at 2050.

Self-calibration and laser energy monitor validations for a double-pulsed 2-μm CO integrated path differential absorption lidar application.

Double-pulsed 2-μm integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval.

Evaluation of an airborne triple-pulsed 2 μm IPDA lidar for simultaneous and independent atmospheric water vapor and carbon dioxide measurements.

Water vapor and carbon dioxide are the most dominant greenhouse gases directly contributing to the Earth's radiation budget and global warming. A performance evaluation of an airborne triple-pulsed integrated path differential absorption (IPDA) lidar system for simultaneous and independent monitoring of atmospheric water vapor and carbon dioxide column amounts is presented. This system leverages a state-of-the-art Ho:Tm:YLF triple-pulse laser transmitter operating at 2.

Fully conductively cooled, diode-pumped Ho:Tm:LuLiF4 laser oscillator/amplifier.

A fully conductively cooled and diode-pumped linear Ho:Tm:LuLiF laser oscillator can generate more than 1 J normal mode pulses at a 10 Hz pulse repetition rate where heat pipes are used for cooling pump diodes and laser crystal. As an amplifier, it can amplify the 80 mJ/180 ns pulses into 400 mJ pulses before the appearance of amplified spontaneous emission (ASE). The ASE threshold is about 5.

Hepatic portal venous gas and "the aquarium sign" due to intussusception in kawasaki disease.

The presence of hepatic portal venous gas (HPVG) may be secondary to bowel necrosis, mechanical distension, or intraabdominal sepsis. We describe an unusual and hitherto unreported presence of HPVG manifesting as gas embolization and the unique "aquarium sign" in a patient of Kawasaki's disease. Continuous passage of bubble-like echoes flowing from the hepatic portal venous system into the inferior vena cava and right-sided chambers of heart was noted on echocardiography.

Lidar backscatter signal recovery from phototransistor systematic effect by deconvolution.

Backscatter lidar detection systems have been designed and integrated at NASA Langley Research Center using IR heterojunction phototransistors. The design focused on maximizing the system signal-to-noise ratio rather than noise minimization. The detection systems have been validated using the Raman-shifted eye-safe aerosol lidar (REAL) at the National Center for Atmospheric Research.

Side-line tunable laser transmitter for differential absorption lidar measurements of CO2: design and application to atmospheric measurements.

A 2 microm wavelength, 90 mJ, 5 Hz pulsed Ho laser is described with wavelength control to precisely tune and lock the wavelength at a desired offset up to 2.9 GHz from the center of a CO(2) absorption line. Once detuned from the line center the laser wavelength is actively locked to keep the wavelength within 1.

1 J/pulse Q-switched 2 microm solid-state laser.

Q-switched output of 1.1 J/pulse at a 2.053 microm wavelength has been achieved in a diode-pumped Ho: Tm: LuLF laser with a side-pumped rod configuration in a master-oscillator-power-amplifier (MOPA) architecture.

Coherent differential absorption lidar measurements of CO2.

A differential absorption lidar has been built to measure CO2 concentration in the atmosphere. The transmitter is a pulsed single-frequency Ho:Tm:YLF laser at a 2.05-microm wavelength.

Precise wavelength control of a single-frequency pulsed Ho:Tm:YLF laser.

We demonstrate wavelength control of a single-frequency diode-pumped Ho:Tm:YLF laser by referencing its wavelength to an absorption line of carbon dioxide. We accomplish this wavelength control by injection seeding with a cw Ho:Tm:YLF laser that can be tuned over or stabilized to carbon dioxide or water vapor lines. We show that the pulsed laser can be scanned precisely over an absorption line of carbon dioxide by scanning the injection seed laser wavelength.