Miniaturized laser heterodyne radiometer for measurements of CO2 in the atmospheric column (original) (raw)
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Conference on Lasers and Electro-Optics, 2016
The miniaturized laser heterodyne radiometer (mini-LHR) is a ground-based passive variation of a laser heterodyne radiometer that uses sunlight to measure absorption of CO 2 and CH 4 in the infrared. Sunlight is collected using collimation optics mounted to an AERONET sun tracker, modulated with a fiber switch and mixed with infrared laser light in a fast photoreciever. The amplitude of the resultant RF (radio frequency) beat signal correlates with the concentration of the gas in the atmospheric column.
2014
In a collaboration between NASA GSFC and GWU, a low-cost, surface instrument is being developed that can continuously monitor key carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). The instrument is based on a miniaturized, laser heterodyne radiometer (LHR) using near infrared (NIR) telecom lasers. Despite relatively weak absorption line strengths in this spectral region, spectrallyresolved atmospheric column absorptions for these two molecules fall in the range of 60-80% and thus sensitive and precise measurements of column concentrations are possible. In the last year, the instrument was deployed for field measurements at Park Falls, Wisconsin; Castle Airport near Atwater, California; and at the NOAA Mauna Loa Observatory in Hawaii. For each subsequent campaign, improvement in the figures of merit for the instrument has been observed. In the latest work the absorbance noise is approaching 0.002 optical density (OD) noise on a 1.8 OD signal. An ov...
Remote Operation of an Open-Path, Laser-Based Instrument for Atmospheric CO2 and CH4 Monitoring
Photonics
The technical specifications and the evaluation of the remote operation of the open-path, tunable diode laser absorption spectroscopic (TDLAS) instrument are presented. The instrument is equipped with two low optical power diode lasers in the near-infrared spectral range for the atmospheric detection of carbon dioxide, methane, and water vapors (CO2, CH4, and H2O). Additionally, the instrument eliminates the requirement of retroreflectors since it detects the back reflection of the laser beam from any topographic target. The instrument was operated remotely by measuring background concentrations of CO2 and CH4 in the atmosphere from 24 November 2022 to 4 January 2023. The accuracy of CO2 and CH4 measurement retrievals on a 200 m laser path was estimated at 20 ppm (4.8%) and 60 ppb (3.1%), respectively. The CH4 accuracy is comparable, but the CO2 accuracy is noticeably lower than the accuracy achieved in local operation. The accuracy issues raised are studied and discussed in terms o...
Measurement of carbon dioxide column via space-borne laser absorption
Proceedings of SPIE, 2007
In order to better understand the budget of carbon dioxide in the Earth's atmosphere it is necessary to develop a global high precision understanding of the carbon dioxide column. In order to uncover the 'missing s i n k that is responsible for the large discrepancies in the budget as we presently understand it calculation has indicated that measurement accuracy on the order of 1 ppm is necessary. Because typical column average C02 has now reached 380 ppm this represents a precision on the order of .25% for these column measurements. No species has ever been measured from space at such a precision. In recognition of the importance of understanding the C02 budget in order to evaluate its impact on global warming the National Research Council in its decadal survey report to NASA recommended planning for a laser based total C 0 2 mapping mission in the near future. The extreme measurement accuracy requirements on this mission places very strong requirements on the laser system used for the measurement. This work presents an analysis of the characteristics necessary in a laser system used to make this measurement. Consideration is given to the temperature dependence, pressure broadening, and pressure shift of the C02 lines themselves and how these impact the laser system characteristics Several systems for meeting these requirements that are under investigation at various institutions in the US as well as Europe will be discussed.
Quantum Electronics, 2019
We consider the application of the heterodyne signal detection technique to measure the atmospheric transmission spectrum in the near-IR range, which makes it possible to measure for the first time the contour of a separate line of the vibrational – rotational CO2 band on the solar observation path with a high spectral resolution of λ/δλ = 108. Together with other characteristics of the instrument, this enables us to measure the carbon dioxide content in the atmospheric column with high accuracy. The experimental setup and measurement technique are described. The existing facilities for measuring the content of greenhouse gases in the atmosphere are compared, demonstrating the possibility of using the near-IR heterodyne spectroradiometry to develop a useful and competitive instrument that can be used in building new networks of ground stations to monitor greenhouse gases.
In situ sensing of atmospheric CO2 with laser diodes near 2.05 μm: a spectroscopic study
Infrared Physics & Technology, 2004
A near-infrared diode laser spectrometer was used in the laboratory to study CO 2 line parameters near 2.05 lm. The spectral region was studied with a new generation of laser: antimonide-based quantum-well diode laser from University of Montpellier--France. One line of the (2 0 0 1) III ‹ (0 0 0) band of CO 2 that is suitable for the in situ sensing of the middle atmosphere has been thoroughly studied at 2.05 lm. The results are compared to previous determinations and available databases. We further demonstrate with this new-generation laser the possibility to detect CO 2 at ground levels using the JETDLAG laboratory spectrometer.
Laser Sounder for Active Remote Sensing Measurements of CO2 Concentrations
2008 IEEE Aerospace Conference, 2008
We report on progress of our C02 laser sounder laboratory breadboard system the goal of which is to measure the integrated column abundance of C02 to better than 1 ppm from low Earth orbit globally, measuring at all latitudes and seasons through day and night. The challenge for an orbiting C02 instrument is to achieve high precision not high sensitivity. We have made simple yet significant improvements to our active, optical-sensing laser-sounder instrument and real-time data processing that now enables absolute absorption measurements to better than ± 0.050O for over 10 hours before re-calibration (equivalent to a lppm precision from orbit). Data from an eight day, 0.8 Km open path comparison test with a LICOR shows excellent agreement.12
Laser sounder approach for measuring atmospheric CO2 from orbit
Proceedings of the …, 2003
We describe progress in developing a laser-based approach for the remote measurement of atmospheric CO 2 from a satellite in low earth orbit. In this method, CO 2 abundance is measured by differential absorption in an overtone band near 1.57 µm. The dry-air mixing ratio can be calculated from the ratio of CO 2 to O 2 , which can be measured using a similar technique applied to an O 2 absorption at 770 nm. A third channel operating at 1.064 µm will be used for cloud and aerosol detection. The approach leverages technology development by the telecommunications industry, using mainly commercially available components, many of which have already been space qualified. Measurement precision better than 1% will be needed to satisfy the scientific requirements. Component stability and noise levels must therefore be thoroughly investigated. In addition, a rigorous calibration strategy will be required. We report initial atmospheric measurements over a horizontal path and results from tests to characterize individual components.
Applied Physics B
We report the development of a laser sonde operated under stratospheric balloons and devoted to the in-situ measurement of carbon dioxide in the upper troposphere and the lower stratosphere. In the 2.68 micron region, strong CO2 transitions are suitable for the in-situ monitoring of carbon dioxide, which gives ∼10% absorption depth and, moreover, antimonide laser diodes are nowadays available that show relevant spectral properties for absorption spectroscopy. The light-weight sensor is based on 50-cm single path configuration and is operated open to the atmosphere. We provide details of the design of the instrument and data processing. The performance and the stability of the instrument were evaluated with the Allan variance technique. The spectrometer was test-flown in the Arctic stratosphere from Kiruna, Sweden and we report preliminary flight results.
Atmospheric CO2 measurements with a 2-μm DIAL instrument
EPJ Web of Conferences, 2018
We report on ground-based atmospheric concentration measurements of carbon dioxide, using a pulsed direct detection differential absorption lidar operating at 2051 nm. The transmitter is based on a tunable parametric source emitting 10-mJ energy, 10-ns duration Fourier-limited pulses. Range resolved concentration measurements have been carried out on the aerosol back-scattered signal. Cloud signals have been used to get long range integrated-path measurements.