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Experimental Digital Twins for Multi-GNSS Integrity Monitoring


TECH FOCUS AREAS: Network Command, Control and Communications; Autonomy; Artificial Intelligence/Machine Learning; General Warfighting Requirements (GWR)


TECHNOLOGY AREAS: Sensors; Space Platform; Information Systems


OBJECTIVE: Develop experimental digital twin concepts for “eCreate before You Aviate” offering new digital engineering perspectives to competitive market-driven acquisition of Multi-GNSS Integrity Monitoring systems, e.g., in how US Space Force should effectively integrate and operate multi-GNSS software-defined receivers equipped with reprogrammable multi-GNSS integrity monitoring for increased anti-jam performance, signal flexibility, SWaP-C reduction, and increased supplier base.


DESCRIPTION:  US Space Force is interested in exploring the value to Multi-Global Navigation Satellite System (Multi-GNSS) of recent developments in digital twin applied to position, velocity, and timing (PNT) information with different levels of integrity, accuracy, continuity, and reliability in GNSS-challenged environments. Digital twining is now an important and emergent design and development trend in many applications such as health, meteorology, manufacturing and process technology, etc. It is best known as a virtual representation of physical assets enabled through data and simulators for real-time forecast, optimization, monitoring, retrospective analysis, and improved decision-making. Multi-GNSS and multi-GNSS integrity monitoring applications could include exploitation of redundancy of observables available from legacy and modernized civil signal operations including non-GPS data sources, detection and identification of possible anomalies corrupting navigation solutions, and receiver autonomous integrity monitoring. Such technical areas typically involve multi-constellation GNSS physically in real-time, inbuilt spoof detection at GNSS navigation receivers, scenarios and integrity risk assessment, statistical hypothesis testing, availability of simulated and live-fed data and advanced analytics in real time.  The topic solicitation envisions that the breakdown of an experimental digital twin should be consisted of three pillars: i) Virtual Twin – creation of virtual representations of different environments and available infrastructures (e.g., with dedicated infrastructure, with ad-hoc infrastructure or with no infrastructure at all), platform dynamics of multi-constellation GNSS, Inertial Measurement Units (IMUs), multi-GNSS receivers accessing a large number of ranging signals from multi-GNSS constellations via S and L bands, real-time IMU measurements, and the possible levels of hybridization within multi-GNSS integrity monitoring systems together with distributed telemetry, tracking and commanding (TT&C) data from control segments and user segments; ii) Predictive Twin – physics based, data driven or hybrid models operating on the virtual twin to predict the requirements for continuous, accurate and robust PNT services, including characterization of spoofing and navigation errors caused by multi-path propagation as well as signal accuracy and availability; and iii) Twin Projection – Integration of insights generated by the predictive twin into the proof of concept of multi-GNSS software-defined receivers equipped with reprogrammable multi-GNSS integrity monitoring for pseudo ranging operations. Proposed solutions are expected to demonstrate the feasibility of applying high-fidelity numerical simulators, physics-informed machine learning and artificial intelligence, data assimilation, hardware and software in the loop, etc. to multi-GNSS systems, received signals for any coverage services, and multi-GNSS integrity monitoring systems. Quantification of experimental characteristics and capabilities such as continuous updates with total integrity risk of positioning errors in near real-time, physical realism at high spatio-temporal resolutions, informed decision-making, and future predictions to be achieved is highly desirable.


PHASE I: Identify relevant characteristics, e.g., infrastructures, platform dynamics, multiple hypothesis solution separation techniques associating with potential multi-GNSS and multi-GNSS integrity monitoring applications and mapping them to corresponding enabling technologies with which digital twins have been previously demonstrated and evaluated for real-time communication of data and latency, physical realism and future projections, continuous model updates and modeling the unknown. Investigate new techniques, methods, and algorithms of representing the effects of GPS spoofing, multi-path propagation, and other factors affecting positioning errors to enable the feasibility of multi-GNSS, Inertial Navigation Systems, and multi-GNSS integrity monitoring applications of experimental digital twin technologies. Specify underlying datasets (e.g., live-fed INS, non-GPS core data, simulated/emulated GNSS signals, etc.) available for research and validated model building, and computational infrastructures.


PHASE II: Develop of an engineering development unit (EDU) to demonstrate the value of such an experimental digital twin in combination of live feeds of C/A and/or M-Code signals, to a continuous, accurate and robust service provision only offered by the multi-GNSS integrity monitoring, of which single GNSS integrity monitoring alone could not meet. Test out hypothetical scenarios for “what if?” analysis, performance gains and risk assessments of countering threats to integrity and exclusivity. Demonstrate physics/knowledge/science-informed machine learning as needed to enable the hybridization of a suite of different GNSS integrity monitoring solutions in addressing operational challenges of data management, data privacy and security, and data quality. Assess quantitative benefits, e.g., near real-time prediction of PNT resiliency in presence of ambiguity resolution of ephemeris, clock errors, interferences, etc. of using the digital twin EDU.


PHASE III DUAL USE APPLICATIONS: With the findings from Phase I and II, the construction of experimental digital twins will help the design of robust and resilient multi-GNSS, multi-GNSS receivers, multi-GNSS integrity monitoring systems and approaches not only during the conceptualization, prototyping, testing and design optimization phase but also during the operation phase with the ultimate aim to use them throughout the whole product life cycle. Potential Phase III military applications include enterprise tech solutions for robust, resilient PNT capabilities with anti-jam, anti-spoof, accuracy, integrity, and signal flexibility. Tech transition plan: Government organizations such as AFRL and SMC sponsor a government reference design of an experimental digital twin of multi-GNSS integrity monitoring systems in collaboration with small business and industry partners. Successful technology demonstrations will inform the technical requirements of future multi-GNSS integrity monitoring acquisitions by Primes and subcontractors. Improved multi-GNSS integrity monitoring and reprogrammability are generally in demand and thus are widely used in proliferated PNT and open architectures across all orbits.


NOTES: 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 proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR Help Desk:




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KEYWORDS: Multi-GNSS; multi-GNSS receivers; multi-GNSS integrity monitoring; simulated/emulated GNSS signals; live fed INS measurements; non-GPS signals; digital twin; virtual twin; predictive twin; twin projection; PNT reprogrammability

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