Atmospheric Lidar with Cross-Track Scanning

An eye-safe, multispectral cross-track scan subsystem with a large receiver aperture and a narrow FOV is proposed for the NASA Cloud Physics Lidar to increase horizontal area coverage. The +/-15 degree cross-track scan capability will cover +/- 5 km from nadir at a 20 km altitude. The cross-track scanner uses a whiskbroom pattern with three simultaneous scans and independent receiver FOV's which provides 30,000 points per sweep. Solar background is reduced with a narrow bandpass filter and a narrow transmitter linewidth with center wavelength control. The scanner accounts for the return pulse lag angle due to pulse time of flight. Vertical resolution is maintained at 30 m. Photon counting SPAD detectors and PMT's are used with photon counting modules and multichannel scalers.