Improvement of SLR accuracy, a possible new step

The satellite laser ranging (SLR) technology experienced a large number of technical improvements since the early 1970's, leading now to a millimetric instrumental accuracy. Presently, it appears as useless to increase these instrumental performances as long as the atmospheric propagation delay suffers its actual imprecision. It has been proposed for many years to work in multiwavelength mode, but up to now the considerable technological difficulties of subpicosecond timing have seriously delayed such an approach. Then a new possibility is proposed, using a device which is not optimized now for SLR but has already given good results in the lower troposphere for wind measurement: the association of a radar and a sodar. While waiting for the 2-lambda methodology, this one could provide an atmospheric propagation delay at the millimeter level during a few years with only little technological investment.