Precise Time and Time Interval (PTTI)

PTTI Pre-Conference Tutorials

1. GNSS Time and Frequency Transfer Techniques
2. Time Scales, Time Keeping, and Redefinition of Time
3. Next-Generation Chip-Scale Clocks and Quantum Sensors
4. Deep-Space Positioning, Navigation, and Timing
5. Advanced Ground and Space Optical Clocks
6. Nuclear Clocks and Test of Fundamental Physics

PTTI Session Topics

Peer review is optional

Perspectives and Updates from National Metrology Institutes in T&F Metrology
Recent work and strategic developments at National Metrology Institutes (NMIs) and Designated Institutes (DIs) worldwide, which remain at the core of the international time and frequency metrology infrastructure. Contributions are invited on methods and technologies for the generation and maintenance of UTC(k); improvements in timescale algorithms; the development and deployment of hardware for timekeeping and dissemination; calibration and traceability services offered to national and international stakeholders; reports on the implementation of optical clocks into institutional timescales; efforts to improve time transfer capabilities; and initiatives aimed at supporting emerging user demands in sectors such as telecommunications, finance, geodesy, and defense. Presenters are encouraged to share insights into institutional strategies for international collaboration, capacity-building, and adaptation to the upcoming redefinition of the SI second. This session aims to foster cross-institute dialogue, highlight best practices, and explore the evolving roles of NMIs in a globally connected metrological ecosystem.
Session Chairs:
Dr. Jeff A. Sherman, NIST
Dr. Héctor Álvarez Martínez, ROA

Engagement of Broader Scientific and Regulatory Communities in T&F Metrology
Presentations from communities and organizations such as ITU, BIPM, IAU, IGS, IERS, ISO, ETSI, IEEE, CNES, NASA, ESA, and others that contribute to or depend on T&F metrology in critical ways. Topics may include the adoption of timing standards, coordination of leap second practices, synchronization challenges in telecommunications, timing in geodesy and Earth observation, and the use of ultra-stable time in astrophysics and space science. The session also encourages reflections on the role of regulatory and scientific communities in supporting international harmonization efforts, interfacing with metrology institutes, and contributing to forward-looking developments in timekeeping, particularly in the context of increasing performance demands and the digital transformation of timing infrastructure.
Session Chairs:
Dr. Joseph Achkar, LNE OP/ITU
Dr. Lukasz Bonemberg, European Commission-Joint Research Centre (JRC)

Advances in Ground Atomic Clocks
Recent progress in the development, evaluation, and application of high-performance ground-based atomic clocks, which continue to drive the frontiers of precision measurement in both fundamental science and applied metrology. Contributions invited are microwave frequency standards, optical lattice clocks, single-ion clocks, and other state-of-the-art systems. Topics of interest include novel interrogation techniques, clock laser stabilization, vacuum and thermal control advances, and innovative approaches to improving accuracy, stability, and robustness. The session also welcomes updates on system-level integration, compact and transportable clock designs, and performance benchmarking across metrological, industrial, and academic environments.
Session Chairs:
Dr. Daphna Enzer, JPL, CALTECH
Dr. Shimon Kolkowitz, UC Berkeley

Advances in Space Atomic Clocks
The development and deployment of current and next-generation space-qualified atomic clocks and oscillators. Contributions are welcome on systems designed for operation in low Earth orbit (LEO), medium Earth orbit (MEO), geostationary orbit (GEO), and deep-space environments, including lunar and interplanetary missions. Relevant topics include advances in space-clock design generally; and more specifically for radiation hardness, vibration tolerance, and thermal stability.  Relevant topics could also address: space qualification and environmental testing procedures; system integration and flight readiness, and on-orbit performance characterization; mission results from existing spaceborne clocks; development of compact and Low-SWaP (Size, Weight, and Power) units; and progress toward space-compatible optical frequency standards. The session encourages forward-looking concepts that aim to extend clock performance, autonomy, and reliability in the increasingly demanding context of space operations.
Session Chairs:
Dr. James Camparo, The Aerospace Corporation
Dr. Jacopo Belfi, Leonardo SPA 

Advances in Low-SWaP Atomic Clocks
Topics of interest include technologies such as chip-scale atomic clocks (CSACs); vapor-cell clocks; miniaturized ion and cold-atom systems; ruggedized designs suitable for operation under harsh environmental condition; advances in SWaP optimization, power management, robustness to shock and vibration; and performance benchmarking across a variety of operational contexts. Applications may span defense and military systems, GNSS-denied navigation, satellite payloads, autonomous platforms, telecommunications infrastructure, and space-based missions. Contributions demonstrating field validation, integration challenges, or transition to manufacturing are especially encouraged.
Session Chairs:
Dr. Jenna Chan, ARL DEVCOM
Peter Cash, Microchip

Environmental Sensitivity of Clocks and Timing Systems
How environmental variables—such as temperature, vibration, pressure, and electromagnetic interference—impact timing systems. Topics include measurement and modeling techniques, sensitivity mitigation, and compliance with IEEE 1193 and similar standards; contributions on test protocols, environmental chambers, robustness testing in mobile and space environments, and techniques for compensating or isolating effects due to changing ambient conditions; both component-level and system-level analyses are welcome, including work on clocks used in field-deployed or industrial applications.
Session Chairs:
Dr. Daniele Monahan, The Aerospace Corporation 
Dr. Judith Olson, HRL Laboratories, LLC

Methods and Algorithms for Timescales and Timing Applications
Algorithmic developments for timescale generation, clock modeling, uncertainty estimation, prediction, filtering, anomaly detection, and new methods of machine learning and neural networks in frequency and timing protocols. Topics may include Kalman filtering, clock ensemble realization and management, timekeeping for space missions, interpolation/extrapolation of noisy data, and predictive models to support robust synchronization in dynamic environments, including anomaly detection and mitigation. Contributions involving optical timescales, data-driven algorithms, or software-defined implementations are especially encouraged.
Session Chairs:
Andrea Auer, German Aerospace Center (DLR)
Dr. James McKelvy, Jet Propulsion Laboratory

NEW! Electronics for Precision Timing Applications
Analog and digital electronics that enable precision timing including noise analysis and mitigation strategies; clock distribution and signal conditioning; electromagnetic compatibility and interference control; compensation for environmental effects, low-phase-noise circuit design, and digital components such as ADCs, DACs, FPGAs, and DSPs. Innovative system integration approaches, including SDR and hybrid architectures, are also welcome.
Session Chair:
Dr. Claudio E. Calosso, INRIM

NEW! Established T&F Transfer Technologies
Techniques for transferring time and frequency, including GNSS, TWSTFT, and fiber-based systems; also addressing calibration, uncertainty management, and hybrid methods. Contributions are encouraged, but not strictly limited to, network-based synchronization, bidirectional optical links, time traceability chains, and improvements to robustness and traceability over long distances. 
Session Chairs:
Calvin Lin, Telecommunication Labs
Dr. Josef Vojtech, CESNET

NEW! Novel Approaches to T&F Transfer
Time and frequency transfer for emerging, terrestrial, or space-based, communication systems and networks. Submissions explore methods beyond the traditional and standardized, including unconventional means of transferring time and frequency using naturally occurring phenomenon, non-traditional communication channels, and other novel related techniques. Theoretical work, simulations, and experimental results that challenge or extend beyond conventional methods, especially in frontier applications, are encouraged.
Session Chair:
Dr. Nathan Barnwell, NIWC Pacific

Timing Architectures and Performance in GNSS Systems
The design and evaluation of timing architectures within GNSS constellations. Topics include onboard clock performance, system time generation, ground-segment synchronization, timekeeping in Earth or cislunar orbit, as well as the evaluation of the performance of new timing services. Submissions may address practical or theoretical frameworks for time distribution across segments, hybrid GNSS systems, or advanced timing schemes for LEO constellations.
Session Chairs:
Dr. Gaetano Galluzzo, European Space Agency (ESA)
Dr. John P. Janis, L3Harris Technologies

NEW! Lunar Timekeeping and Navigation
The need for an independent lunar timekeeping and its synchronicity to the Earth’s time is an important aspect to be solved including the PNT solutions for the moon orbiter and landing missions, such as Artemis. The lunar missions require precise, resilient, and reliable PNT solutions for both navigation and effective communications considering the planned human missions to the moon. Progress toward realization of lunar timekeeping and lunar coordinated time (LTC), synchronization of UTC to LTC, and atomic clocks on the moon, and novel time transfer methods are of particular interest.
Session Chairs:
Dr. Thejesh N. Bandi, The University of Alabama
Cheryl Gramling, NASA

NEW! Transitioning to a New Definition of the SI Second
The transition to a revised definition of the second, driven by advancements in optical clock technology addressing both the technological innovations, and the organizational and scientific challenges that must be addressed to implement this change. Key topics will include: the scientific rationale behind redefinition; advances in optical clock, their dissemination and comparison; milestones, criteria, and the timeline for redefinition; comparative analysis and understanding of redefinition options; impact on timekeeping: dissemination, calibration, and infrastructure; emerging quantum technologies; and next-generation timekeeping solutions.
Session Chairs:
Dr. Nils Nemitz, NICT
Dr. Demetrios Matsakis, Masterclock

International Technical Meeting (ITM)

ITM Session Topics

All manuscripts will be peer reviewed

Advancements in Navigation Algorithms
Application of modern machine learning techniques to enhance navigation, including deep neural networks, boosting, graphical models, and both interpretable and unsupervised learning methods. Algorithms and techniques leveraging network connectivity to assist and improve navigation. Innovative estimation methods such as distributed state estimation, advanced filtering, and integration of 3D models, landmarks, and other data sets. Utilization of cloud and crowd-sourced data for navigation. Development of algorithms for new applications and fresh approaches to modeling and numerical challenges in navigation and positioning. Robust positioning techniques suitable for challenging environments. Collaborative and cooperative positioning algorithms and theories. 
Session Chairs:
Dr. Élisa Gallon, Airbus Defense and Space
Dr. Zhen Zhu, Eastern Carolina University

Alternatives, Backups, Complements to GNSS
Alternative PNT solutions for applications such as aviation, maritime, transportation, railway, and space flight. Technologies addressing the vulnerability of GNSS users to natural threats and security vulnerabilities. New positioning methods or technologies, navigation aids, low Earth orbit satellites, terrestrial transmitters or pseudolites. Technologies that complement or replace GNSS during outages. Solutions for multipath and degenerate geometries on positioning. Examination of atmospheric distortions and integrity monitoring for signals of opportunity or other radionavigation.
Session Chairs:
Dr. Tim Needham, Ohio University
Dr. Joshua Morales, StarNav

Atmospheric Effects, GNSS Remote Sensing, and Scientific Applications
GNSS technologies used for environmental and scientific monitoring, modeling and measuring atmospheric effects such as tropospheric delays and ionospheric delays and sensing Earth’s surface changes. Applications in radio occultation, ionospheric scintillation, and detecting significant geophysical events such as earthquakes and volcanic eruptions. GNSS reflectometry for environmental monitoring of atmosphere, soil moisture, flood surveillance, oceanography, ice, and inland water bodies. Novel GNSS applications exploring gravitational measurements and dark matter detection.
Session Chairs:
Dr. Shrivathsan Narayanan, Collins Aerospace
Dr. Hyeyeon Chang, University of Colorado, Boulder

Autonomous Navigation and Safety-Critical Applications
Navigation systems for assisted and autonomous vehicles and mobile platforms. Integrity monitoring for safety-critical applications using GNSS and additional sensors. Support through assistance and cloud-based technologies for reliable and secure autonomous systems. Enhanced safety, availability, and efficiency in guided vehicle systems and pilot assistance within demanding environments. Safety protocols, integrity standards, and certification criteria for autonomous navigation and guidance systems. This session also welcomes contributions on integrity monitoring and fault detection methods for safety-critical systems, including ARAIM, RAIM, and other receiver-based integrity mechanisms.
Session Chairs:
Andrew Videmsek, Reliable Robotics
Dr. Hadi Wassaf, DOT Volpe Center

GNSS Security: Interference, Jamming, and Spoofing
Detection, characterization, and geolocation of intentional and unintentional interference. Mitigation strategies and improved robustness against spoofing, jamming, and general interference. Signal-to-noise ratio characterization in the presence of interference and its effects on GNSS receivers. Development of software and hardware solutions, including signal processing and authentication. Fault detection and integrity assessment techniques related to spoofing or interference, including satellite or constellation-level anomaly detection. Architectures for incorporating backup and complementary PNT technologies for detecting and mitigating GNSS jamming and spoofing. Applications in robust positioning and secure time transfer. Threat modeling and analysis of GNSS disruption events. Spectrum monitoring and localization of interference sources using ground, airborne, and spaceborne receivers. Use of smartphone GNSS data for spectrum monitoring. Techniques to enhance GNSS robustness through advanced signal processing, authentication, and complementary PNT methods.
Session Chairs:
Dr. Eric Vinande, Air Force Research Laboratory
Dr. Birendra Kujur, Illinois Institute of Technology

Innovations in Navigation for Smartphones and Wearables
Applications requiring reliable positioning solutions in smartphones and wearables. Enhanced positioning techniques in smartphones and wearables for improved indoor, outdoor, and urban-canyon navigation. Improved stochastic modeling of GNSS observables. Algorithms and multi-sensor fusion for enhanced accuracy in varied environments. Use of smartphone raw GNSS measurements for scientific applications in geosciences. Detection and mitigation of jamming and spoofing threats in smartphone-based positioning systems. Quality assessment of GNSS antennas in smartphones and wearables, including evaluation of antenna phase center offsets and variations.
Session Chairs:
Dr. Jaymin Patel, Apple
Dr. Li-Ta Hsu, Hong Kong Polytechnic University

Next-Generation Satellite Navigation Technology
Innovations in future generation satellite navigation technology; advancements in satellite constellations. Strategies and approaches for the interoperability and compatibility of GNSS constellations. Enhancements in GNSS signal structure through improved codes and data messages. Cutting-edge technologies, including highly stable frequency standards onboard navigation satellites and intersatellite links. Development of new navigation systems in low Earth orbit (LEO). Updates on constellation characteristics and programmatic elements, along with ground control and monitoring segments. Evaluation of the performance of new satellites and services. Examination of RF compatibility, mutual interference, and antenna pattern characterization.
Session Chairs:
Dr. José-Ángel Ávila-Rodríguez, European Space Agency
Zach Clements, University of Texas at Austin

PNT Solutions for Space Applications
Emerging applications in space positioning. Design and implementation of navigation systems for in-space applications, including space-grade GNSS receivers for re-entering vehicles. Enhancing spacecraft positioning with inter-satellite links and satellite laser ranging. Innovative approaches for satellite constellation build-up and maintenance. Application of GNSS for orbit and attitude determination, including precise orbit determination. Navigation techniques for the Moon, and cislunar and translunar areas beyond Earth’s geosynchronous belt. Relative navigation near asteroids and comets. Advanced space positioning techniques including snapshot-based positioning both on the ground and in space. Interplanetary navigation technologies using GNSS, other RF signals, electro-optical systems, and magnetic fields. Enhanced PNT solutions at LEO, GEO, and HEO. Utilization of environmental features and signals like pulsars, clock aid, and integration with other sensors for cooperative positioning.
Session Chairs:
Dr. Sabrina Ugazio, Ohio University
Dr. Nathan Green, CTSi 

Precise GNSS Positioning Applications
Advances in GNSS positioning methods including multi-GNSS precise point positioning (PPP), real-time kinematic (RTK), PPP-RTK, and network RTK. Development of partial ambiguity resolution techniques and integer ambiguity resolution (IAR) using high precision geodetic-quality and/or low-cost antennas and receivers, including smartphones. Utilization of positioning algorithms with space-based augmentation services like the Galileo high accuracy service (HAS). Multi-constellation solutions employing single-/multi-frequency geodetic and/or low-cost receivers/antennas. Characterization and modeling of GNSS satellite clock errors; precise orbit determination for scientific purposes. Interoperability of GNSS correction services with diverse user equipment, ensuring robustness against multipath, interference, and other local effects. Comprehensive GNSS signals and performance characterization and monitoring. Applications of high precision and high integrity GNSS positioning in fields like crustal and structural deformation monitoring, GNSS seismology, atmospheric remote sensing, and precision agriculture. New algorithms and methods enhancing precise positioning techniques and robustness against local environmental effects. Integrity characterization for high-precision positioning, including protection level estimation and continuity monitoring.
Session Chairs:
Dr. Safoora Zaminpardaz, RMIT University
Dr. Thyagaraja Marathe, Xona Space Systems 

Receiver Design, Signal Processing, and Antennas
GNSS receiver signal processing techniques for enhanced resiliency in challenging environments such as indoor, urban canyons, foliage, scintillation, high dynamics, and under interference. Design of receivers optimized for modernized GNSS signals. Development and application of software-based GNSS receivers. Enhancements in acquisition and tracking sensitivity, robustness, and accuracy. Mitigation strategies for multipath and non-line-of-sight (NLOS) signals. Design and evaluation of GNSS antennas and antenna electronics. Utilization of mass-market and low-cost devices in GNSS applications. Calibration processes for multi-GNSS receivers. Utilization of multi-GNSS signal simulators for testing and development.
Session Chairs:
Mark Carroll, AFRL Sensors Directorate
Emilio Pérez-Marcos, German Aerospace Center (DLR) 

NEW! Resilient Navigation for Civil Aviation
Mitigating the effects of jamming, spoofing, or any form of radio frequency interference (RFI) on civilian aircraft.  Seamlessly maintaining and quantifying integrity to provide safe, secure and robust navigation services, including, but not limited to: en-route services, like performance-based navigation (PBN) or required navigation performance (RNP), as well as landing services like GBAS approach service types (GAST) or localizer performance with vertical guidance (LPV). Papers may describe novel antennas, algorithms, navigation systems, monitoring and warning systems, data fusion and integration, and innovations that provide safe, secure and robust navigation systems for civil aviation. This session also welcomes papers on GNSS augmentation systems (SBAS, GBAS, ARAIM), integrity monitoring, and continuity in aviation environments.
Session Chairs:
Dr. Okuary Osechas, ZHAW
Glenn Colby, CatShot 

Sensor-Fusion for GNSS-Challenged Navigation
Integration of data from multiple sensors and information sources in GNSS-challenged environments. Application of estimation theories, algorithms, and data processing techniques. Testing and results from integrating diverse sensors in challenging environments: GNSS, IMUs, odometers, magnetometers, radar, lidar, cameras, barometers, map, infrared, and ultrasound sensors. Sensor fusion with signals of opportunity (SOOP). Navigation strategies for urban canyons, indoor settings, and GNSS-denied environments. Use of low-cost devices for pedestrian, automotive and UAV applications.
Session Chairs:
Dr. Cagatay Tanil, Amazon Prime Air
Dr. Andrey Soloviev, QuNav

NEW! Validation and Assurance of AI-Based Autonomous Systems
In navigation systems, integrity refers to the trust placed in the correctness of information and the system’s ability to alert users when that information becomes unreliable—critical for safety in applications like aviation. As we move toward AI-based autonomous systems, a similar concept of integrity is needed to ensure these systems operate reliably under diverse conditions. This session invites methods for evaluating, validating, and assuring AI-based autonomous systems used in PNT applications. Topics include transparency, explainability, and accountability in AI-driven decision-making; techniques for performance validation during development and assurance during deployment, especially in dynamic and uncertain environments; and detection and mitigation of out-of-distribution behavior and domain shifts. Contributions may include system architectures, testbeds, monitoring tools, certification approaches; case studies from safety-critical domains such as aviation, automotive, maritime, and space systems; and formal methods, testing frameworks, and standards for AI reliability and integrity.
Session Chair:
Dr. Sahil Ahmed, Illinois Institute of Technology