Water vapor temperature and wind velocity measurements from space using 2 um Tm:Ho;YAG

摘要

In meteorological and climatological fields, the scientific community increasingly needs global measurements of key atmospheric parameters with high spatial resolution (horizontal as well as vertical): the future spaceborne lidars are promising instruments for those missions. The next spaceborne applications of lidars are related to `simple' backscatter lidars (ATLID type, currently studied at ESA); the following generation of potentially spaceborne lidars are DIAL and Doppler wind lidars, presenting a higher level of complexity than the previous ones, mainly due to the large power and complex signal processing required. At present, considered wind lidars are based on CO$-2$/ lasers, whose space compliance is still to be demonstrated, while alexandrite or titanium sapphire lasers have been considered for water vapor and temperature measurements. However, flashlamp pumping poses severe constraints (efficiency, thermal dissipation, ...): on the other side, the recent developments achieved in solid-state technology allow us to envisage direct diode pumping as the most promising possibility for both previous applications. All these reasons have induced ESA to ponder a future mission dedicated to water vapor, temperature and wind velocity measurements and using an eye-safe wavelength in solid-state technology. Involved in this ESA contract are Aerospatiale and its subcontractors, namely, Quantel (laser, France) with the support of the University of Berne, Switzerland; Alenia (receiver, Italy); Teldix (lag-angle compensator, Germany); and the lidar teams of the Laboratoire de Meteorologie Dynamique and Service d'Aeronomie, France; and of Enea and the University of Rome, Italy. We have selected Tm,Ho:YAG technology emitting at 2 $mu@m; the main first results of our studies are presented and include: investigation of spectral lines, transmitter and receiver requirements, and parametric studies leading to the final instrument design.