Low SWAP LIDAR Instrument for Arctic Ice Sheet Mass Balance Monitoring

The Arctic sea ice cover plays a major role in governing the exchange of energy between the ocean and atmosphere in the Polar Regions. As such, observations of ice extent and thickness, including temporal growth and melt cycles, improves our understanding of the ongoing global climate changes, and enhances our ability to predict future changes. Despite continual improvements in global climate models, there is still greater difficulty in reproducing the current climate in the Arctic than elsewhere in the world. LIDAR measurements of mixed type and water surface elevation or profiling have not yet been successful from space, and they do not characterize the surface, with sufficient detail and timeliness for albedo to be estimated, so that the local mass balance of the various Arctic sea ice types, including snow cover and open water, cannot be correlated with heat balance estimates. Proposed is a small size, weight, and power (SWAP) dualmode twocolor laser altimeter boresighted with a radiometrically calibrated CMOS imager. The small unmanned aerial system (SUAS) optimized instrument, operates seamlessly over ice, water, snow, ground, and vegetation. Real time fullwaveform processing of 532nm and 1064 nm laser returns, allows surface classification, and, combined with the radiometricallycalibrated multicolor [red, green, blue, and nearinfrared (R,G,B,NIR)] CMOS imager, allows normalized difference vegetation index (NDVI) to be calculated for each pixel. Optimized for the harsh Arctic conditions, the low SWAP dualmode altimeter is implemented with a offaxis, afocal optics, a miniature dualband high rate pulsed laser, and highgain, lownoise segmented avalanche photodiode (APD) arrays. A fixed holographic element scanner achieved efficient ground coverage, and the data is digitized, georeferenced and processed, in real time, using a FPGA processor before being stored in 1 TB of solid state memory. In Phase I, the SUASoptimized dualmode altimeter was developed, and the optics, scanner, laser, receiver, and GPS/IMU components were specified. Design trades were then conducted to achieve the performance goals within the SUAS rigorous SWAP constraints. The laser and avalanche photodiode (APD) receivers were fabricated and tested, and an endtoend performance simulation was performed, verifying performance. In Phase II, the dualmode altimeter will be fabricated and characterized. Real time processing and calibration firmware will be developed, and the system will be demonstrated in field tests. Commercial Applications and Other Benefits: Currently, the top three global uses of LIDAR mapping data are: 1) topographic mapping; 2) flood risk assessments; and 3) watershed analysis. Natural resource applications in geology, water, and forestry, Hydrology / flood applications, and power utility applications are expected to grow, as a result of the innovations flexible deployment and lower cost. The technology also has applicability to 3D military imaging, automotive imaging, gesture recognition, and humancomputer interfacing.