Global Positioning System GPS for Submersibles By Marvin

Global Positioning System (GPS) for Submersibles By Marvin B. May Rodney A. Martin Bereket Tanju Robert A. Lopez, CAPT USN C. Ryan Tang ICS 280 Ubi. Comp Winter 2006 9/25/2020 1

Introduction ○ Motivation for TRANSIT satellite navigation system came submarine community ● Periodic updates used to augment inertial navigation system ○ GPS faces unique technical challenges in submarine environment 9/25/2020 2

Challenges ○ Attenuation of the GPS Signal Reflection at air/water interface ● Attenuation due to lossy nature of seawater ● ○ Effect of Residual Seawater Increases voltage standing wave ratio ● Alters phi/theta components of the radiated far field ● ○ Ducting Atmospheric phenomenon ● Extends transmission of radio waves ● 9/25/2020 3

Challenges ○ Time RMS Navigation Error Lack of sensitivity to GPS error ● Can store ephemeris data on sub ● ○ Receiver Initialization-Time to First Fix Want to minimize exposure time ● Need to search many phase/frequency bins to get P/Y code ● ○ Antenna Considerations Separate antenna from antenna electronics ● Interference from transmission antennas ● 9/25/2020 4

Proposed Solutions ○Covert GPS Navigation Capability (COGNa. C) ●Storage GPS receiver recirculates signal in non realtime ●Minimizes exposure time at the cost of post exposure processing ○Trailing Wire GPS Antenna ●Provides GPS at depth ●Submarine tied to GPS buoy ●Severe space constraints ●Can be towed or stationary 9/25/2020 5

Proposed Solutions ○Submersible Underwater GPS Aided Receiver (SUGAR) ●Use GPS buoy with avionics grade inertial navigator ●Keeps track of submarines relative distance from the buoy ○GPS Acoustic Ranging Net (GARN) ●Deploy multiple GPS buoys ●Use SONAR to determine submersible position relative to the net ●Provides precise and continuous location while within range 9/25/2020 6

Questions? 9/25/2020 7