Tunable narrow linewidth laser source for a methane lidar

et al. 2017

J. Appl. Remote Sens

Section: Discussionsupporting

confidence: 58%

Methane optical density measurements with an integrated path differential absorption lidar from an airborne platform

Riris

et al. 2017

J. Appl. Remote Sens

“…In addition, for a space mission we are aiming for a simple and efficient single stage -not a complex multi-stage -OPA based on quasi-phase matching (QPM). In this configuration, we have observed that the OPA output linewidth does not fully converge to the seed linewidth, giving wide side lobes, especially when pump and seed fluences are high and low, respectively 49 . Back-conversion and parametric amplification of the seed's side lobes are possible causes.…”

Section: Gsfc Measurement Approachmentioning

confidence: 97%

The challenges of measuring methane from space with a LIDAR

Riris

et al. 2019

CEAS Space J

The global and regional quantification of methane fluxes and identification of its sources and sinks has been highlighted as one of the goals of the NASA 2017 Earth Science Decadal Survey. Detecting methane from space and airborne platforms with an active (laser) remote sensing instrument presents several unique technology and measurement challenges. The instrument must have a single frequency, narrow-linewidth light source, and photon-sensitive detector at the right spectral region to make continuous measurements from orbit, day and night, all seasons and at all latitudes. It must have a high signal to noise ratio and must be relatively immune to biases from aerosol/cloud scattering, spectroscopic and meteorological data uncertainties, and instrument systematic errors. At Goddard Space Flight Center (GSFC), in collaboration with industry, we have developed an airborne instrument to measure methane. Our instrument is a nadir-viewing lidar that uses Integrated Path Differential Absorption (IPDA), to measure methane near 1.65 µm. We sample the absorption line using multiple wavelengths from a narrow linewidth laser source and a sensitive photodetector. This measurement approach provides maximum information content about the CH4 column, and minimizes biases in the XCH4 retrieval. In this paper, we will review our progress to date and discuss the technology challenges, options and tradeoffs to measure methane from space and airborne platforms.

“…The development of the OPA technology for LIDAR use has been discussed in detail previously. 18,20 We scan the LIDAR wavelength by changing the injection current of the DFB LD. 18,19 Our pulsed LIDAR uses 20 wavelengths spanning 17.6 GHz (0.16 nm) around the 1650.9 nm methane transition.…”

Section: Measurement Approach and Instrumentmentioning

confidence: 99%

Airborne measurement of atmospheric methane concentration using pulsed lidar

Ramanathan

et al. 2012

SPIE Proceedings

We demonstrate the airborne measurement of atmospheric methane using a pulsed lidar at 1650 nm using an integrated path differential absorption scheme. Our seeded nanosecond-pulsed optical parametric amplifier (OPA)-based instrument works up to the highest altitudes flown (>10 km). Our airborne measurements are in good agreement with the expected atmospheric absorption. The difference between the measured absorption expressed in terms of the differential optical depth (DOD) and the predicted DOD calculated using Global Modeling and Assimilation Office (GMAO) data is 0.027±0.038 (standard deviation), with the DOD ranging from 0.5 to 2. For large sections of the flight, the measured absorption profile agrees within 2% rms of the predicted absorption profile. Overall, the retrieved atmospheric methane concentration lies within 11% of the true concentration, the latter estimated from our onboard in situ Picarro cavity ring down spectrometer.