A document discusses solutions to the problem of submarines having to rise above water to detect airplanes in the general vicinity. Two solutions are provided, in which a sensor is located just under the water surface, and at a few to tens of meter depth under the water surface.
The first option is a Fish Eye Lens (FEL) digital-camera combination, situated just under the water surface that will have near-full-hemisphere (360° azimuth and 90° elevation) field of view for detecting objects on the water surface. This sensor can provide a three-dimensional picture of the airspace both in the marine and in the land environment.
The FEL is coupled to a camera and can continuously look at the entire sky above it. The camera can have an Active Pixel Sensor (APS) focal plane array that allows logic circuitry to be built directly in the sensor. The logic circuitry allows data processing to occur on the sensor head without the need for any other external electronics.
In the second option, a single-photon sensitive (photon counting) detector-array is used at depth, without the need for any optics in front of it, since at this location, optical signals are scattered and arrive at a wide (tens of degrees) range of angles.
Beam scattering through clouds and seawater effectively negates optical imaging at depths below a few meters under cloudy or turbulent conditions. Under those conditions, maximum collection efficiency can be achieved by using a non-imaging photon-counting detector behind narrowband filters.
In either case, signals from these sensors may be fused and correlated or decorrelated with other sensor data to get an accurate picture of the object(s) above the submarine. These devices can complement traditional submarine periscopes that have a limited field of view in the elevation direction. Also, these techniques circumvent the need for exposing the entire submarine or its periscopes to the outside environment.
This work was done by Hamid Hemmati, Joseph M. Kovalik, and William H. Farr of Caltech, and John D. Dannecker of QinetiQ NA Corp. for NASA’s Jet Propulsion Laboratory. NPO-47916
This Brief includes a Technical Support Package (TSP).
Hemispherical Field-of-View Above-Water Surface Imager for Submarines
(reference NPO-47916) is currently available for download from the TSP library.
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Overview
The document presents a technical support package for NASA's Hemispherical Field-of-View Above-Water Surface Imager for submarines, identified as NPO-47916. Developed at NASA's Jet Propulsion Laboratory (JPL), this innovative technology aims to enhance submarine situational awareness by enabling the detection of aerial threats without the need for surfacing, thus reducing the risk of detection by adversaries.
The system offers two primary options for underwater sensing. The first option utilizes a fish-eye lens coupled with a digital camera positioned just below the water's surface. This configuration provides a near-complete hemispherical field of view (360° azimuth and 90° elevation), allowing for comprehensive monitoring of the airspace above the submarine. The camera is equipped with an Active Pixel Sensor (APS) that integrates logic circuitry for on-sensor data processing, enabling the detection of specific light signatures, such as moving light sources.
The second option employs a photon counting detector array positioned at depths of several meters. This approach is advantageous in conditions where optical imaging is compromised due to beam scattering in cloudy or turbulent waters. The system can achieve high collection efficiency and utilize synthetic aperture techniques to enhance spatial resolution, allowing for effective imaging even at significant depths (up to 250 meters under clear conditions).
The document highlights the novelty of these devices, which complement traditional submarine periscopes that have limited elevation field-of-view. By using these advanced sensors, submarines can maintain a low profile while effectively monitoring their surroundings.
Applications of this technology extend beyond military use, with potential benefits for homeland security and border patrol operations. The research and development of this system stem from NASA's broader efforts in optical communications and faint signal detection in deep space, showcasing the dual-use nature of the technology.
The document concludes with acknowledgments of the research conducted at JPL under NASA's sponsorship, emphasizing the importance of compliance with export regulations and the proprietary nature of the information contained within. For further inquiries, contact details for JPL's Innovative Technology Assets Management are provided. Overall, this document outlines a significant advancement in submarine technology, enhancing operational capabilities while ensuring stealth and safety.
