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Portable Atomic Clock

Description:

TECHNOLOGY AREA(S): Electronics

OBJECTIVE: Develop, demonstrate, and deliver a portable (rackmount) optical atomic clock with volume < 20 L, weight < 30 kg, power < 100 W, and stability (< 3 x 10-13 at 1 second) that can be utilized in Army systems requiring precise timing in global positioning system (GPS)-denied environments.

DESCRIPTION: Precise timing is critical for numerous Army applications such as navigation, communications, surveillance, and synchronization of sensors and systems. Assured positioning, navigation, and timing (PNT) solutions currently rely on acquiring GPS signals, which may not be readily available in increasingly contested environments and therefore may need to hold precise time for minutes to hours. To ease reliance on GPS, long-holdover clocks with cost, size, weight, and power (CSWaP) appropriate for various DoD platforms are necessary to enable mission-critical functions even in contested environments. Focused research over the past 10-15 years has led to portable timing technology advances including miniaturized vapor cell microwave atomic clocks [1] that are now commercially available. The chip-scale atomic clock (CSAC) has impressive stability performance at its size, weight, and power (SWaP), but it suffers limitations in long-term performance due to various drift mechanisms that are currently being addressed through exploration of new physics approaches. Optical atomic clocks have shown superior stability performance [2] but face challenges to being deployed outside of the laboratory, such as technical complexity and reliability in dynamic environments. Certain proposed optical clock architectures [3] have shown relative simplicity over others but have not yet been realized in a form factor that is appropriate for SWaP-constrained platforms nor have they been characterized for long-term reliability in dynamic environments. The goal of this SBIR is to develop and demonstrate an optical clock that provides a combination of performance and CSWaP that currently deployed atomic clocks cannot offer.

PHASE I: * We would like this topic to be Direct to Phase II if possible, as commercial development has already demonstrated feasibility **Determine technical feasibility of realizing a portable optical clock that can be evaluated for deployment in Army applications. Develop a preliminary clock design, model key elements of the proposed clock, and identify subcomponents that demonstrate a clear path to achieving a fractional frequency instability of < 3 x 10-13 at 1 second and reaching a flicker floor of 10-14 at 10,000 seconds with size, weight, and power less than commercial rackmount cesium beam tube clocks [4]. Phase I deliverables include a design review including expected device performance as well as quarterly reports and a final report presenting Phase II plans.DIRECT TO PHASE II: Offerors interested in submitting a Direct-to-Phase-II proposal in response to this topic must provide documentation to substantiate that the scientific and technical merit and feasibility described in the Phase I section of this topic has been met and describes the potential commercial applications. Documentation should include all relevant information including, but not limited to: technical reports, test data, prototype designs/models, and performance goals/results.

PHASE II: * We would like this topic to be Direct to Phase II if possible, as commercial development already demonstrated feasii **Develop an integrated optical clock system design (physics package, electronics, firmware/software). Build the clock to specifications determined in the Phase I design study and refined through proof-of-concept breadboard demonstration of subcomponents.Construct and demonstrate a prototype clock, and validate its performance by measuring short-term frequency stability, long-term drift, and flicker floor outlined in Phase I. Perform temperature cycling and inversion tests to determine environmental and acceleration sensitivities. Phase II deliverables include a clock prototype for further Army evaluation, as well as quarterly and final reports.Awardees of this topic will have the ability to voluntarily participate in quarterly soldier touch-points, a 1-2 day trip within the continetal US. Touch point will be provided free of charge however participating companies must travel and participate out of company internal operating budgets. Soldier touch point details will be provided to awardees under this topic at Phase II award.

PHASE III: Developments in this program should enable widespread deployment of clocks with stability exceeding current rackmount primary frequency standards. These clocks could lead to more reliable and robust global positioning, synchronization, and time-keeping in GPS-denied environments, as well as secure communications. Potential commercial applications include precise synchronization of telecommunication networks for high-bandwidth communications, next-generation satellite atomic clocks for global positioning, and improved reliability of business activities in the event of GPS outages (e.g. time-stamping of global business transactions).

KEYWORDS: optical atomic clock; GPS-denied environments; positioning, navigation, and timing (PNT); precise timing

References:

Lutwak, R., Rashed, A., Varghese, M., Tepolt, G., LeBlanc, J., Mescher, M., Serkland, D. K., Geib, K. M., Peake, G. M., Römisch, S., "The Chip-Scale Atomic Clock - Prototype Evaluation," Proceedings of the 39th Annual Precise Time and Time Interval Meeting, Long Beach, California, November 2007, pp. 269-290.; W. F. McGrew, X. Zhang, H. Leopardi, R. J. Fasano, D. Nicolodi, K. Beloy, J. Yao, J. A. Sherman, S. A. Schäffer, J. Savory, R. C. Brown, S. Römisch, C. W. Oates, T. E. Parker, T. M. Fortier, A. D. Ludlow. Towards the optical second: verifying optical clocks at the SI limit. Optica, 2019; 6 (4): 448 DOI: 10.1364/OPTICA.6.000448; Ye, Jun & Ma, Long & Hall, John. (2001). Molecular Iodine Clock. Phys. Rev. Lett.. 87. 270801. 10.1103/PhysRevLett.87.270801.; https://www.microsemi.com/product-directory/cesium-frequency-references/4115-5071a-cesium-primary-frequency-standard

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