Other
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.a41d0142a&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #A41D-0142
Other
1610 Atmosphere (0315, 0325), 3305 Climate Change And Variability (1616, 1635, 3309, 4215, 4513), 3360 Remote Sensing, 3394 Instruments And Techniques
Scientific paper
Accurate measurements of tropospheric CO2 abundances with global-coverage and monthly temporal resolution are needed to quantify processes that regulate CO2 exchange with the land and oceans. To meet this need, the 2007 Decadal Survey for Earth Science by the US National Research Council recommended a laser-based CO2 measuring mission called ASCENDS. In July 2008 NASA convened a science definition workshop for ASCENDS, which helped better define the mission and measurement requirements. We have been developing a technique for the remote measurement of tropospheric CO2 concentrations from aircraft and spacecraft. Our immediate goal is to develop and demonstrate the lidar technique and technology that will permit measurements of the CO2 column abundance over horizontal paths and from aircraft at the few-ppmv level. Our longer-term goal is to demonstrate the capabilities of the technique and instrument design needed for an ASCENDS-type mission. Our approach uses the 1570-nm band and a dual channel laser absorption spectrometer (ie DIAL used in altimeter mode). It uses several tunable fiber laser transmitters allowing simultaneous measurement of the absorption from a CO2 absorption line in the 1570 nm band, O2 extinction in the oxygen A-band, and surface height and aerosol backscatter in the same path. It directs the narrow co-aligned laser beams toward nadir, and measures the energy of the laser echoes reflected from land and water surfaces. The lasers are tuned on and off the sides of CO2 line and an O2 line (near 765 nm) at kHz rates. The receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface along with scattering from any aerosols in the path. The gas extinction and column densities for the CO2 and O2 gases are estimated from the ratio of the on and off line signals via the DIAL technique. We use pulsed laser signals and time gating to isolate the laser echo signals from the surface, and to reject those from thin clouds and aerosols. Generally signal- to-noise ratios of 700 are required, and the CO2 estimates are sensitive to small drifts and other errors. We have constructed breadboard versions of the CO2 and O2 sensors, which use tunable fiber lasers and a 20 cm diameter telescopes. We have used them to make measurements of gas absorptions over 206 and 400-m open horizontal paths. These have been in several sessions extending over multiple days, and have allowed us to assess the measurement stabilities and to compare its estimates to readings from an external CO2 sensor. Airborne demonstration flights are being prepared for fall 2008. We have also calculated several characteristics of the technique for space and have performed an initial space mission accommodation study. In the presentation we will describe how this approach compares to the measurement needs as summarized from the ASCENDS workshop, and will give an update on measurement demonstrations and projected instrument capabilities.
Abshire James B.
Allan Graham R.
Riris Haris
Stephen Mark A.
Sun Xiaosong
No associations
LandOfFree
Laser Sounder Approach for Measuring Atmospheric CO2 Concentrations for the ASCENDS Mission does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Laser Sounder Approach for Measuring Atmospheric CO2 Concentrations for the ASCENDS Mission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laser Sounder Approach for Measuring Atmospheric CO2 Concentrations for the ASCENDS Mission will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1233550