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High Performance, Small Size, Weight, and Power (SWaP) Clock for Unmanned Aerial Vehicles (UAVs)


TECHNOLOGY AREA(S): Sensors, Electronics, Battlespace 

OBJECTIVE: Develop a high performance, reduced Size, Weight, and Power (SWaP) clock for Navy Unmanned Aerial Vehicle (UAV) applications. 

DESCRIPTION: The Navy is seeking to develop alternative routing of data through airborne Unmanned Aerial Vehicle (UAV) nodes to enable high data bandwidth, robust connectivity, and routing flexibility between platforms in the surface fleet. This will allow for increasing the diversity of airborne platforms (including Unmanned Aircraft Systems (UASs)), which can provide new sensors and robust, anti-jam communications. A critical component necessary for this capability is a highly accurate clock that can act as a time and frequency reference to ensure that communications across the network are synchronized properly. The clock needs to have the flexibility to scale in SWaP, and must be suitable for airborne applications. This flexibility would enable networked communications and sensor data fusion utilizing a variety of airborne platforms. This will greatly increase data throughput, system availability, system accuracy, and the ability to dynamically collect and route information, thereby improving the fleet’s ability to execute complex multi-ship missions. Time and frequency reference clocks are used to very accurately determine time-of-day of an event, time duration of an event or interval between two events, and frequency or rate of a repeated event. Within a networked system, these clocks are used to ensure that data transmission and reception is correctly synchronized from point-to-point, that data has not become stale due to latency issues, that information from sensors and weapons systems can be coordinated, and that communications have not been interrupted or compromised. Since the beginning of naval explorations, accurate clocks have allowed for precise geolocation. Typically, the most accurate clocks have been those based upon an atomic standard from the National Institute of Standards and Technology (NIST). Until recently, atomic clocks were expensive and too large to be installed on smaller, more portable tactical platforms constrained by SWaP. This has prevented the Navy from using the most accurate clocks available on smaller platforms. This is no longer the case as emerging atomic clock technology, such as Chip Scale Atomic Clocks (CSACs) and Miniature Atomic Clocks (MACs), offer high levels of timekeeping performance with reduced SWaP impacts. CSACs, which were developed by Defense Applied Research Projects Agency (DARPA), are approximately 15 cubic centimeters (cm³). CSACs are accurate to 50 nanoseconds (ns) while typically consuming less than 150 milliwatts (mW) of power resulting in minimal impact to the host platform. This reduction in SWaP is achieved using advanced physical techniques like Coherent Population Trapping (CPT) and technologies such as vertical surface emitting cavity lasers, which eliminate requirements for higher SWaP components such as conventional lamps. MACs, which were developed by industry, are based on a standard rubidium or cesium physics package but have continued to evolve to meet customer demands for smaller SWaP applications. They also use CPT and other advanced hardware components to reduce SWaP while providing high levels of performance. While CSAC and MACs both offer significant performance improvements, further innovation is required to improve performance another order of magnitude. For example, CSACs (Allan Deviation of 10^(-10) at t = 1 s) and MACs (Allan Deviation of 10^(-11) at t = 1 s) have greatly improved frequency stability over other legacy clocks and crystal oscillators but are still well off performance levels of top-of-the-line Cesium frequency standards (Allan Deviation of 10^(-12) at t = 1 s). An example of a reduction to medium term Allan deviation is achieved through light intensity optimization and compensation for laser frequency detuning. Alternatively, many commercial off-the-shelf (COTS) timekeeping technologies rely on the use of information derived from global positioning system (GPS) signals through a Selective Availability Anti-spoofing Module (SAASM) to discipline and control the frequency of the local clock oscillator to improve overall stability. In summary, the Navy seeks a “one stop shop” time and frequency clock to satisfy mission requirements, to operate across demanding environmental conditions (high acceleration and vibration), and to disseminate time and frequency to a broad variety of local onboard users and systems, all while minimizing SWaP. The Phase II effort will likely require secure access, and NAVSEA will process the DD254 to support the contractor for personnel and facility certification for secure access. The Phase I effort will not require access to classified information. If need be, data of the same level of complexity as secured data will be provided to support Phase I work. Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. Owned and Operated with no Foreign Influence as defined by DOD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Security Service (DSS). The selected contractor and/or subcontractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this contract as set forth by DSS and NAVSEA in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advance phases of this contract. 

PHASE I: Develop a concept for a High Performance, Small SWaP Time and Frequency Reference clock that will utilize state-of-the-art timekeeping technology stated in the topic description. Demonstrate the feasibility of the concept in meeting Navy needs and establish that the concept can be feasibly produced. Feasibility will be established by some combination of initial analysis or modeling. The Phase I Option, if awarded, will include the initial design specifications and capabilities description to build a prototype in Phase II. Develop a Phase II plan. 

PHASE II: Based on the Phase I results and the Phase II Statement of Work (SOW), produce and deliver a prototype accompanied by appropriate data analysis and modeling. Evaluate the prototype High Performance, Small SWaP Time and Frequency Reference clock to determine its capability in meeting Navy requirements. The prototype will demonstrate its ability to meet requirements for Navy UAV applications. Testing, evaluation, and demonstration are the responsibility of the company and should therefore be included in the Phase II proposal. Either demonstration will take place at a company or Government-provided facility. The company will prepare a Phase III development plan to transition the technology for Navy. It is probable that the work under this effort will be classified under Phase II (see Description section for details). 

PHASE III: Support the Navy in transitioning the technology to Navy use. Further refine the prototype according to the Phase III development plan for evaluation to determine its effectiveness and reliability in an operationally relevant environment. Support the Navy in the system integration and qualification testing for the technology through platform integration and test events managed by Program Executive Office Integrated Warfare Systems (PEO IWS) to transition the technology into UAV applications. There is the prospect of significant interest from the private sector for an affordable, small form factor Time and Frequency Reference clock that can produce different timing signals to meet various subsystem requirements. These include mobile infrastructure, wired communications, aerospace, research, medical and instrumentation/timing. 


1: Delcolliano, John, and Olson, Paul. "It’s All About Time." Army AL&T Magazine. July-September 2016. Pages 91-93.

2:  National Institute of Standards and Technology. "NIST-F1 Cesium Fountain Atomic Clock." NIST Physical Measurement Laboratory Time and Frequency Division. 19 September 2016.

3:  Lombardi, Michael. "Fundamentals of Time and Frequency." CRC Press. 2002.

4:  Zhang, Yaolin, Yang, Wanpeng, Zhang, Shuangyou, and Zhao, Jianye. "Rubidium chip-scale atomic clock with improved long-term stability through light intensity optimization and compensation for laser frequency detuning." Journal of the Optical Society of America B. Volume 33. Issue 8. Pages 1756-1763. 8 July 2016.

5:  Lombardi, Michael. "The Use of GPS Disciplined Oscillators as Primary Frequency Standards for Calibration and Metrology Laboratories." Measure Journal. Volume 3. Number 3. Pages 56-65. September 2008. NSCL International.

KEYWORDS: Smaller SWaP For Atomic Clocks; Time Reference For UAVs; Frequency Reference For UAVs; Unmanned Aerial Vehicle (UAV); Unmanned Aircraft Systems (UASs); Cesium Frequency Standards 


Mrs. Onekki Montgomery 

(202) 781-1186 

Mr. David Trumpoldt 

(202) 781-0581 

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