Mobilizing optical underwater imaging and communications Derek Alley Dr. Brandon Cochenour Dr. Linda Mullen NAVAIR Laser/Magnetics Advanced Technology Branch Patuxent River, MD, USA Mobilizing optical underwater imaging and communications

Applications Oceanography: Bottom mapping/profiling Oil and Gas: Monitoring oil rigs/pipelines Defense: Detection, ranging, and high speed comms Bathymetry/Ranging Imaging Comms/Networking

Complications Clear night/clear water, more light better vision Foggy night/murky water, more light more scattering (clutter) Car with high beams How do we distinguish the object from the clutter?

Hybrid LIDAR-RADAR Combine benefits of light and radar –Transmission through water –RADAR/RF signal processing (this is where SDRs come into play)

Architecture exploits Laser Receiver Platform Can increase source/receiver separation, but increases platform size Fog lights – increases distance between line of sight and illuminated scene to improve visibility Laser Receiver Platform

Tx and Rx fully autonomous  Compact size  Optimize Tx–to-obj distance, Maximize Rx-to-obj distance Image reconstruction via digital comms data encoded into the interrogating beam  RF carrier modulates intensity of laser light. Sync/Comms encoded on carrier via FSK  Simultaneous communications and imaging Thru-the-surface imaging  Wavy water surface doesn’t distort imagery since Tx is below surface Scalable - Distributed Sensing  Multiple Tx or Rx using separate frequency channels similar to cell phones The bistatic approach Tx

Why SDRs? Flexibility – TX: Frame rate, resolution, swath, modulation scheme Frame rate vs resolution Comms speed vs BER – RX: Gain, BW, averaging Image SNR vs resolution

Field Tests R/V Rachel Carson (Univ. of MD)

Object 3m below surface Object 8m below surface File: NAVAIR Brief 2.3m 3 to 8m 1m *Fixed source to target geometry TARGET Field Test Results

Mobile TX and Multiple RX

Platform REMUS 600 AUV: Collaboration with University of MD at Horn Point, MD –Large –Stable –Mature technology –Perfect 1 st step

REMUS HW - Transmitter

TX software operation N210 w/ WBX for FSK communications 70 MHz carrier 250kbps data rate N210 w/ LFTX daughterboard drives the galvo 500 lines/sec zig-zag scan 40 degree 1 meter standoff Sub-millimeter spatial resolution

GRC flow graph Comms (FSK) (WBX) Scanner control (LFTX)

REMUS HW - Receiver

Lab Testing

Future work Tank testing Multi-receiver module Modified OpenROV –> CUTEI (Compact Underwater Temporally Encoded Imager) –Small –“dumb” –$ (cheap) OpenROV CUTEI

Concluding Remarks We’re putting things in motion We use SDRs as the backbone of our comms and imaging system –First USRPs underwater! Necessary step to the implementation on mobile autonomous vehicles with a distributed sensing architecture

Thank You!

Backup Slides

Multi-receiver module Receiver