LATMIX Planning Meeting LIDAR for LATMIX December 8-9, 2009 Seattle, WA Brian M. Concannon Jennifer E. Prentice NAVAIR brian.concannon@navy.mil jenifer.prentice@navy.mi (301) 342-2034 (301) 342-2025 Jim Ledwell Gene Terray WHOI jledwell@whoi.edu eterray@whoi.edu (508) 289-3305 (508)289-2438 Miles Sundermeyer UMASS, Dartmouth msundermeyer@umassd.edu (508) 999-8892

Lidar 101 Amplitude (dB) Time (depth) Laser Receiver Amplitude (dB) Backscatter Less Turbid Animated slide showing how the lidar return signal is dependant on the properties of the water. Need to modify to show two slabs of water with different IOP’s and corresponding lidar return signal. Time (depth) The slope of the lidar waveform is dependent on the inherent optical properties and is different for different water types. Bottom return

Lidar Data Acquisition & Processing Depth (m) Time or Distance Color Coded Slope vs. Depth Depth (m) Amplitude (dB) A=e-2KsysD Depth (m) Ksys (m-1) Waveform Slope vs. Depth Animated slide showing basic processing technique for in-field viewing of data. Color scale for last protion of animation is arbitrary but Ksys = 0.1 = blue and Ksys=0.7=black.

Lidar System Flown 2008 and 2009

Telescope Modifications for LATMIX Dye Return Dichroic Beam Splitter Lidar Return Simultaneous collection of Blue backscatter and Green dye fluorescence

Lidar Volume Mapping Approaches

LATMIX Lidar Vertical Resolution Altitude T0 f (laser pulse width, system bandwidth, dig sample rate) Laser pulse width = 10 ns -> 1.1 meter depth in water System Bandwidth = 100 MHz (log amp, PMT) = 10 ns Digitizer Sample Rate = 400 MSPS = 2.5 ns per sample Bottom Line: Depth Resolution ~ 1meter with 4X oversample Note: relative depth accuracy ~10 centimeters

LATMIX Lidar Horizontal Resolution f (scan pattern, pulse rate, platform speed, platform altitude) Scan Pattern = circular cone Full Angle = 39 deg Scan Rate up o 15 Hz Pulse Rate – up to 1700 Hz Platform Speed = 100 m/s (1 km/10 sec) Conservative Example: 100 m/s along track 305 m alt 1000 Hz PRF 11.5 Hz scan rate Swath Width = 216 m Min Horizontal = 8 m Min Along Track = 8 m Notes - back scan fill - Peak perf ~ 6 m Across Track Res is f (scan speed, PRF) A/C track Swath Width is f (scan angle, Alt) Along Track Res is f (scan speed, A/C speed)

Flight Patterns vs. Time Evolution Racetrack 9 km/ (100 m/s) = 90 sec = 1.5 min 5.5 km 30 sec leader (3 km) 0.100 m/s x T sec = N km For T =45 sec: Whole Pattern = 7 minute Across track map speed = 1.5 km/hr (20% overlap) 30 sec leader (3 km)

Flight Patterns vs. Time Evolution Dog Bone 5.5 km 30 sec leader (3 km) 100 m/s x T sec = N km T = 45 sec Whole Pattern = 9 min Revisit mid-point every 5 min Across track map speed = 1.9 km/h (33% overlap, ) 30 sec leader (3 km) 17.5 km/ (100 m/s) = 175 sec = 3.25 min

Performance and Flight Limitations Lidar Fog, Low Clouds, Rain Must Monitor Op Area Aircraft/Crew Predicted or Actual Lightning Strong Turbulence 12 – 14 hour duty day

Dye mapping Opportunity Sept 12, 2008 Intensity vs. Position Dye Returns Depth vs. Position Dye Returns 024315-024335 UTC Equivalent to 024301-024319 GPS Time

Environmental Transect June 24, 2009 N. Sargasso Sea Hatteras Data Start and End Latitude (deg)

01:24:18 (UTC) End of Transect SE

01:30:35 UTC Southbound Pass

01:38:30 UTC Northbound Pass

Lidar Data Analysis Goals The measured backscatter (480 nm) and fluorescence (~520 nm) intensities will be used to Map the 3D dye concentration with 5-10 m horizontal and ~1 m vertical resolutions Study the temporal evolution of the dye patch Estimate the along- and cross-isopycnal diffusivities Track the floats and AUV

Questions?

BACKUP

Mapping Floaters and AUV’s Blue Return ~ E x Area x R( bb) ~ E x 20 m2 x 0.0005 ~ E x 0.01 AUV Return ~ E x Area x R( bb) ~ E x ? m2 x ? ~ E x 0.25 x 0.2 ~ E x 0.05 Automating sorting through the data to find 1 shot requites the AUV/floater return look VERY different

Mapping Floaters and AUV’s Lidar will only detect light within it’s scanning, instantaneous FOV 45º LED upward looking cone of light LED - LIDAR can detect 10-6 W easily - Ratio of LIDAR Aperture to LED Spot at 325m separation = 10-5 - attenuation in water ~ e-1.5 = 0.22 - LED Power > 0.2 W (515 to 525 nm) Retro-Reflective Surface - 0.1 m2 Retro tape on ground required ND 3 in Rx for 5 m spot at 305 m - attenuation in water ~ e-3 = 0.05 - 0.01 m retro-tape = easy detection LED retro

01:43:45 UTC Eastbound Pass

01:51:53 UTC Westbound Pass

Intensity vs. Position Dye Returns Sept. 12, 2008 Forward Scan Aft Scan

Depth vs. Position Dye Returns Sept. 12, 2008 Depth calculated at 50% rise of max peak Surface onset calculated at 50% rise of surface flash

Light in the Ocean http://oceanexplorer.noaa.gov/explorations/04deepscope/background/deeplight/deeplight.html Basic illustration of the depth at which different colors of light penetrate ocean waters. Longer wavelength light (reds and oranges) is absorbed more quickly than shorter wavelength light (greens and blues).

HITS 4.1 All Tanker Types + Merchants TW