Accurate global measurements of tropospheric CO₂ mixing ratios are needed to better understand the global carbon cycle and the CO₂ exchange between land, oceans and atmosphere. NASA Goddard Space Flight Center (GSFC) is developing a pulsed lidar approach for an integrated path differential absorption (IPDA) lidar as a candidate for the NASA’s planned ASCENDS mission to allow global measurements of atmospheric CO₂ column densities from space. Our group has developed and demonstrated an airborne IPDA lidar for this purpose. It uses two tunable pulsed laser transmitters allowing simultaneous measurement of a single CO₂ absorption line in the 1570 nm band, absorption of an O₂ line pair in the oxygen A-band (765 nm), and atmospheric backscatter profiles in the same path. In the airborne lidar, both lasers are pulsed at 10 kHz, and the two absorption line regions are sampled at typically a 300 Hz rate. A space version of this lidar must have a much larger laser power-telescope area product to compensate for the signal losses in the ~40x longer range. An analysis of signal to noise ratios indicated that for a 400 km orbit, a 1.5 m diameter telescope and a 10 second integration time, that 1.5 to 2 mJ laser energy is required to attain the needed measurement precision. To meet the laser energy requirements we have pursued two parallel power-scaling approaches for the space laser. These include a single-amplifier approach consists of a multi-pass Er:Yb:Phosphate glass based planar waveguide amplifier (PWA) and a parallel amplifier approach using multiple (typically 8) large mode area (LMA) fiber amplifiers. In this paper we summarize the laser amplifier design approaches and preliminary results.

Date Published: 20 February 2015
PDF: 10 pages
Proc. SPIE 9342, Solid State Lasers XXIV: Technology and Devices, 93420M (20 February 2015); doi: 10.1117/12.2080792

Published in SPIE Proceedings Vol. 9342:
Solid State Lasers XXIV: Technology and Devices
W. Andrew Clarkson; Ramesh K. Shori, Editor(s)