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Description
Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) Opportunity Announcement
HR001121S0007-09
Enduring Spatially-Continuous Sound Velocity Profiler
Which program will fund this topic? = SBIR
What type of proposals will be accepted?
Both Phase I and Direct to Phase II (DP2)
Technology Area(s): Battle Space, Ground/Sea Vehicles
DARPA Program: Manta Ray, Arctic
TOPIC OVERVIEW
a. Objective
Develop a sound velocity profiler for use on unmanned underwater vehicles (UUVs) capable of spatially continuous and temporally enduring measurements across a vertical depth band of the ocean environment as an alternative to current point measurement and single-use expendable devices.
b. Description
Definitions:
· "Sensor component" is the primary sensor(s) that enables the measurement of the surrounding ocean.
· "Velocity profiler device" enables simultaneous measurements of the sound velocity profile across the full-depth of a vertical column of the ocean. The velocity profiler device includes a sensor component, algorithms, and other mechanisms necessary to complete the sensing as described in this topic.
· "Payload module" is the UUV hull-conforming section that hosts the velocity profiler device and mates to a host UUV or surrogate platform. When the vertical profiler device is stowed, the payload module should conform to the UUV outer mold line.
· "Sensor system" includes the UUV payload module when integrated with and hosting the velocity profiler device.
· "Host platform" is the UUV (or surrogate such as a buoy or surface vessel for purposes of at-sea demonstration) that integrates and hosts the sensor system.
The sound velocity profile within a vertical column of the ocean provides key input into many oceanographic uses due to the impact the speed of sound has on the propagation of undersea acoustics. Understanding the sound velocity profile for a given region enables the identification and characterization of acoustic phenomena for use in passive acoustic monitoring, active sonar transmission, and acoustic communications. The current state of practice for sound velocity measurements primarily uses either point measurements or an expendable probe to obtain a single full-depth profile. Point measurements may be taken by a conductivity, temperature, and depth (CTD) probe estimating the sound speed based on the primary environmental factors which influence it. Sound velocity probes may directly measure sound speed by active acoustic emission across a known distance. These probes are typically mounted to an ocean buoy, a manned or unmanned vessel, or fixed to infrastructure and therefore only measure the sound velocity at their current position and depth.
To obtain a measurement of the full sound velocity profile within a vertical column, expendable bathythermographs (XBTs) or CTD sensors are typically deployed for a single-use measurement. The use of these expendable devices is greatly limited onboard small platforms with limited payload volume such as UUVs. Alternatively, a profiling float equipped with a point measurement device may traverse up and down the water column to generate a profile; however, this solution results in a measurement that is time-delayed and potentially spatially displaced, limiting the accuracy and timeliness of the measurement. Profiling floats further require movement of the device through the water column, which may not be operationally prudent or feasible for a UUV.
This SBIR topic will design, develop, and test a velocity profiler device capable of simultaneous measurements of the sound velocity profile across the full depth of a vertical column of the ocean. A vertical profile of at least 300m depth is desirable to achieve a meaningful measurement. The velocity profiler device will be deployed onboard UUVs, and therefore, must be designed for use within the constraints of size, weight, and power (SWaP) for a notional UUV host vehicle, including consideration of the form factor for the payload module.
Sensor system design guidelines for this SBIR topic include the following:
· Payload module size is at the discretion of the proposer. Due to intended integration within UUVs, a notional volume constraint consisting of a cylindrical form factor of 0.53 meters or smaller diameter and length of 2 meters or less is encouraged.
· The sensor system should nominally be neutrally buoyant in seawater. Weight for the sensor component, electronic and mechanical components, energy storage, and any required ballast or buoyancy compensation should be accounted for within the volume of the payload module.
· Power for the sensor system should be provided by energy storage integrated within the payload volume. Power should not be drawn from the host platform.
· Communications with the host platform are allowed to facilitate deploy/retrieve signals and pass environmental information to the host platform.
· Solutions that allow for frequent sampling of a water column over the duration of several months are highly desirable.
· Solutions that allow for dynamically configurable temporal measurement intervals between continuous and periodic are desirable. The sampling duty cycle(s) and corresponding energy budget of proposed solutions should be substantiated in the proposal. If a dynamically configurable temporal measurement interval is proposed, a minimum of best- and worst-case energy budgets should be described and substantiated.
· A vertical profile of at least 300m of the water column is desired for purposes of the Phase II demonstration. Measurement over a greater range of depths, inclusive of spanning full ocean depth, is highly desirable. Depth tolerance of greater than 1000m is highly desirable as the sensor may be deployed from UUVs, which are operating at depth, as opposed to being deployed from the ocean surface.
The sensor system is intended to be both re-usable and enduring; therefore, the sensor system should be able to survive multiple deployments and stowing cycles over the course of a host platform's lifetime. While deployed into the ocean column, spatially continuous sampling of sound speed within a vertical column is required. Solutions that use mechanical raising and lowering a sensor across various depths other than initial deployment are therefore not desired. The sensor system should be survivable and operable across the full global range of ocean environments to include the Arctic under-ice environment.
Any empirical sound velocity model(s) used should:
· Clearly state all variables, constants, and units
· Clearly state ranges of validity for all variables
· Demonstrate traceability to the full global range of ocean environments to include the Arctic under-ice environment.
Solutions may measure sound velocity by any means; however, active acoustic transmissions are not considered desirable.
Proposals should also include the following additional sensing modality information:
· Detail and substantiate the proposed sensing modalities to include expected times to reach a stabilized state after any change in ambient conditions. A stabilized state is defined for this solicitation topic as equivalent to 95% of the steady-state level approached with unlimited wait time.
· Detail and substantiate the expected accuracy (including expected root mean square error values) of sound velocity measurements and any primitive measurements, including how the proposed approach sufficiently bounds an accurate sound velocity profile calculation.
Novel solutions which address portions, but not all, of the guidance of this SBIR topic, may be considered on a case-by-case basis. Examples include revolutionary new approaches for sound velocity measurement that do not span the full depth range
indicated or a velocity profiler device capable of spanning the full ocean depth that does not fit within the nominal SWaP constraints provided.
· Incremental changes from the current state of practice are not desired.
· Expendable or single-use solutions are not desired and will be considered non-compliant with the research objectives of this SBO and therefore non-conforming per Section I.b.
Details regarding the timing of milestones may be found in Phase I and Phase II descriptions below. The proposal scope should include all testing logistics and costs to include (if applicable) but not limited to the use of host platforms, integration of the sensor
system to the host platform, host platform and sensor system operations, laboratory expenses, and any environmental permitting associated with at-sea testing.
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