Development of a Differential Absorption Lidar (DIAL) for Carbon Sequestration Site Monitoring
Abstract
Rising levels of carbon dioxide (CO2) in the Earth’s atmosphere have been identified as a major contributor to climate change. Geologic carbon sequestration has the potential for mitigating CO2 emission into the atmosphere by capturing CO2 at power generation facilities and storing the CO2 in geologic formations. Several technological challenges need to be overcome for successful geologic sequestration of CO2 including surface monitoring tools and techniques for monitoring CO2 sequestration sites to ensure site integrity and public safety. Researchers at Montana State University are developing an eye-safe scanning differential absorption lidar (DIAL) capable of spatially mapping above-ground CO2 number densities for carbon sequestration site monitoring. The eye-safe scanning CO2 DIAL utilizes a temperature tunable fiber pigtailed distributed feedback (DFB) laser operating wavelength of 1.573 μm to access CO2 absorption features. The output of the DFB laser is split using an inline fiber splitter with part of the light sent to an optical wavemeter to monitor the operating wavelength of the laser transmitter. The remaining light is modulated using an inline acousto-optic modulator producing a pulse train with a 20 kHz pulse repetition frequency and a 2 μs duration. This pulse train is amplified in a commercial fiber amplifier producing up to 80 μJ per pulse energy. The output from the fiber amplifier is sent horizontally through the atmosphere and the scattered light is collected using a 28 cm diameter commercial Schmidt-Cassegrain telescope. The light collected by the telescope is collimated and focused into a multimode optical fiber. A fiber coupled photomultiplier (PMT) tube is then used to monitor the light collected by the DIAL receiver. Data is collected in the following manner. The DFB laser is tuned to the online wavelength of the CO2 absorption feature and data is collected for a user defined time. A feedback loop utilizing the optical wavemeter is used to maintain the online wavelength operation of the DFB laser. The signal from the PMT is summed using a multichannel scalar and is read by the computer. The DFB laser is then tuned to the offline wavelength and the process is repeated. The range resolved number density is then calculated using the DIAL equation. This presentation will focus on the design and performance of the eye-safe scanning CO2 DIAL. The initial testing of the CO2 DIAL produces CO2 number densities over a 3 km range with 300 m range resolution.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A23B0238J
- Keywords:
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- 0480 BIOGEOSCIENCES / Remote sensing;
- 3360 ATMOSPHERIC PROCESSES / Remote sensing