Dr. Jianping Mao - 613 Seminar Series

Global measurement of atmospheric CO2 concentration from space is greatly desired for carbon cycle sciences and climate change studies. The ultimate challenge for CO2 remote sensing from space is to achieve the unprecedented measurement precision, which is 1 part-per-million or 0.25% at current level of atmospheric CO2 on regional scale, in order to significantly reduce current large uncertainties in global and regional carbon budget estimates. Current spaceborne carbon missions such as GOSAT and OCO-2, similarly use one weak CO2 absorption band at 1.6 um, one strong CO2 absorption band near 2 um and the O2 A-band at 0.76 um to retrieve atmospheric column-averaged CO2 concentration with regard to dry air. The measurement requirements and the challenges of these passive remote sensing carbon missions will be reviewed and discussed in this presentation. NASA Goddard Space Flight Center is developing an active laser approach to measure atmospheric CO2 from space as a candidate for NASA’s future space mission ASCENDS (Active Sensing of CO2 Emission over Nights, Days, and Seasons). This approach uses two pulsed lasers to simultaneously measure both CO2 and O2 absorption at a number of wavelengths across a CO2 line at 1572 nm and an O2 line at 764 nm to retrieve atmospheric CO2 concentration. Goddard’s CO2/O2 sounders flew and were tested during ASCENDS airborne science campaigns in the past few years. Measurement strategy of Goddard’s CO2/O2 laser sounders will be reviewed and recent results from ASCENDS airborne science campaigns will be presented in this talk.