SBIR-STTR Award

We propose a key innovation to improve wavelength-sensitive lidar measurements (such as wind velocity) using photon-counting receivers. A novel binning technique to track the wavelength shifts of the outgoing laser pulses on a per-shot basis before accumulation in the receiver electronics is described. This allows creation of a narrow histogram in the backscattered signal accumulation process while using less expensive, less stable lasers than are traditionally required. This technique relaxes the stringent stability requirements on the laser, and therefore its size, weight, complexity, and cost. We propose to demonstrate the technique in existing lidars more compact and suitable for airborne platforms in terms of size, weight and power requirements of the system. We utilize recent solid-state laser and high-speed signal processing technologies in the wavelength tracking system. The direct application of the wavelength corrector is in a direct detection Doppler wind lidar. This innovation will significantly reduce the cost of wind lidar systems permitting their installation at airports to look for dangerous wind shears as well as for weather forecasting. Also, this innovation will significantly reduce the cost of a space-based Doppler wind lidar system because of the relaxed laser stability requirements.

We propose to develop and demonstrate an receiver system utilizing our novel technique for tracking and compensating for laser wavelength shifts in lidar systems. During Phase 1, we demonstrated that in addition to tracking and correcting for laser frequency drift, the system is able to track and correct for etalon frequency drift (in fact, only this relative frequency drift can be tracked). Data was collected before, during and after a frequency drift over a period of time typical of lidar data integration times. It was seen that integrating without the correction resulted in data too blurred to have any value, but that the correction system compensated for the shift and allowed for proper wavelength measurements. We now look to incorporate this technique into a lidar receiver system and demonstrate its viability in measuring wind velocity. This receiver would prove the ability to reduce the cost and technical difficulties in building a wind lidar system both for NASA programs (NASA-GSFC CATS wind lidar) and commercial systems for use in weather forecasting and airport wind shear monitoring.