N211-067 TITLE: Atomic Inertial Sensor as an Alternate Position Source
RT&L FOCUS AREA(S): Quantum Science
TECHNOLOGY AREA(S): Weapons
The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.
OBJECTIVE: Develop atomic inertial sensors that advance the state of the art in inertial navigation.
DESCRIPTION: The success of U.S. Navy missions depends on personnel and platforms having access to accurate and reliable position, velocity, attitude, and time information. Maritime platforms specifically need this information continuously to support safety of ship, weapons deployment, and network communications and geo-registration. The DoD developed Global Positioning System (GPS) to provide accurate, worldwide, all-weather, continuous position and time information to warfighters. As a result, GPS is the primary positioning and time source for maritime surface platforms. However, GPS is susceptible to interference and may not be continuously available. Consequently, in the absence of GPS, other technology is sought to provide positioning and timing information to meet mission support.
Many military platforms also usually deploy inertial navigation systems along with GPS. Inertial navigation systems are continuous, all-weather sources of position, velocity, and attitude information. Inertial navigation systems are not susceptible to interference in the same manner as is GPS. In addition, many maritime platform missions can be met with a military grade inertial navigation system. Inertial systems drift over and require periodic fixes to reset their position. Typically, an inertial navigation system will be corrected by fixes to GPS or some other fix source, such as a visual source, a radar contact, or some other navigational feature. In the event of a prolonged period of GPS not being available and no other usual sources being available, additional sources of position fixing are needed.
Inertial measurement sensors based on atomic interferometry solve the problem of sensor drift by providing measurements of acceleration and rotation with very low bias instability and random walk. This high performance is essential for GPS-denied inertial navigation, because position errors grow quadratically in time, proportional to random walk in the inertial sensors. Atomic interferometry uses wave-particle duality to measure accelerations and rotations as interference effects. These methods are precise because atoms have an exact internal electronic structure, which can be manipulated by electromagnetic radiation. The typical atomic interferometer is conceptually similar to a Mach-Zehnder interferometer, but with laser pulse induced Rabi oscillations enacting the behavior of beam splitters and mirrors. In laboratory settings, atomic interferometers have demonstrated super strategic-grade performance with long-term stabilities in the nano-g accelerometers and nano-radian/sec gyroscopes.
Atomic interferometers have previously been deployed on ships and airplanes with µg and µrad/s sensitivity, but in general there are a few hurdles to deploying this technology in defense operations. This technology currently exists in the commercial market in the form of scalar quantum gravimeters (single-axis/1DOF accelerometers), but for the most part the technology has been funded and developed only for defense applications. In addition, navigation requires inertial measurement at frequencies well above 100 Hz, but atomic interferometer sensitivity decreases at higher frequencies, since atoms spend less time experiencing the acceleration or rotation. These devices must also have size, weight, and power, and cost (SWaP-C) low enough to be combined into a full inertial measurement unit (IMU) with gyroscopes and accelerometers along 3 spatial axes (for a total of 6 degrees of freedom). Other problems include the 2p-phase ambiguity, which limits the dynamical range of the atomic interferometer, wavefront curvature in lasers, and eliminating environmental noise.
An aspirational SWaP-C for a strategic-grade 6DOF IMU post-2020 is less than $750,000, 40 liters, 250 Watts, and 40 kg. Previous efforts by DARPA include PINS/High Dynamic Range Atom Sensors and Systems (HiDRA II) and Chip-Scale Combinatorial Atomic Navigator (C-SCAN). C-SCAN sought to create a 6DOF strategic-grade IMU based on atomic interferometry within a 1 cubic inch and 1-Watt package. The result was the production of a 2DOF IMU with strategic-grade performance as an accelerometer and navigation-grade performance as a gyroscope. A related effort, Cold Atom Microsystems (CAMS) dramatically reduced the SWAP-C of atomic clocks relative to chip-scale atomic clocks. The technology sought should focus on either improving contrast to create a super strategic-grade IMU or on reducing SWaP-C to produce a chip-scale IMU with performance comparable to the PINS/HiDRA II 2DOF IMU.
The technology should target one of three areas: component development, strategic-grade IMU development, or 6DOF navigation-grade IMU development.
Component development should focus on R&D in the area of compact lasers, modulators, shutters, vacuum systems, or small-scale electronics. Lasers should have narrow linewidth (10 dB), or low wavefront curvature (< 1 W) or pumpless. Electronics should be low power and ruggedized to support the other components.
Strategic-grade IMU development should improve the quality of existing atomic interferometer sensor technology by improving performance or reducing SWaP-C as defined hereafter. The ideal IMU achieves continuous-strategic grade measurements at an instability of 1 nrad/s, obtains continuous measurements at a high frequency (> 100 Hz), eliminates background noise at the µrad/s level, and maintains contrast in a dynamic environment. These goals can be supported through many-photon momentum transfer, co-sensor integration, rotation compensation with mirrors, continuous-beam atomic sources, atom-number squeezing, atomic gradiometry, wave-front control, or other innovative methods. A proposed atomic interferometer sensor should be able to reduce SWaP-C without degrading performance or to improve performance without increasing SWaP-C. An IMU should cover as many degrees of freedom as possible.
The technology will undergo an independent evaluation at a Government-provided facility to show it will function in a maritime environment. An IMU should function to specification for an indoor ship-motion simulation test. Components should maintain performance for realistic variations in temperature, pressure, vibration, ship-motion, and supplied power but not ruggedized for warship shock and environmental conditions. System navigation performance shall be tested without continuous GPS aiding for a period of at least 100 hours to measure long-term performance and stability.
Navigation-grade IMU development should produce a fully functional 6DOF based on currently existing atomic interferometer technology. Steps in this direction would be combining currently existing single-axis and dual-axis technology to produce a 6DOF navigation-grade IMU or developing ultra-low SWaP-C single and dual-axis devices, which will later be combined to form the full IMU. It is also possible to construct a 6-axis inertial sensor directly as was done by Canuel et al. in 2008. However, the final product should be field deployable in the marine environment using modular construction to fit through 24" doorway. The device should function on a dynamic platform with angular rates up to 0.3 rad/s, tilting of up to 60 degrees, and accelerations as high as 5 m/s (with SWaP equal to or less than 1110 lbs., 600VA max power draw with 600w max heat load, and 13 ft3 total volume, and functions in a shipboard environment. (0-95% humidity, 0-35oC). The technology sought will result in a resilient and accurate source of position and velocity information to U.S. Navy platforms. This information is needed to assure that platforms can meet mission need in the absence of GPS.
PHASE I: Develop a concept that characterizes atomic interferometry sensors that improves the inertial sensors for maritime platforms. Establish feasibility of an approach through analysis, modeling, and simulation to show the concept will meet the required parameters in the Description. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.
PHASE II: Design, develop, and deliver a prototype of the system described in Phase I. Demonstrate that the prototype meets the capabilities detailed in the Description during independent evaluation conducted at a Government-provided facility.
PHASE III DUAL USE APPLICATIONS: Assist the Navy in transitioning the technology to Navy use. The prototype will be tested on a maritime platform to demonstrate performance of the prototype and the associated system.
The technology will be highly valuable in the shipping industry and any at-sea situations where GPS is not always available and high accuracy is a requirement. If SWaP support is needed, aircraft and spacecraft are additional platforms that would benefit. R&D in supporting components will also enhance commercial electronics and the development of other next-generation sensors.
KEYWORDS: Inertial Navigation Sensors; Cold Atom; Atomic Interferometry; Laser Pulse; Gyroscope; nano-g Accelerometer
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