Precise Time and Time Interval (PTTI)

PTTI Pre-Conference Tutorials

• GNSS (for time transfers)
• Atomic Clocks
• Optical Clocks
• Optical Transfers
• Optical Combs

PTTI Session Topics

ION PTTI Plenary Session

Session Chair:

Advanced and Future Clocks
Clocks are needed for timekeeping, navigation, positioning, communication, science and exploration in both terrestrial airborne and space applications. The development of clocks is driven by technological advances in these areas that push for devices with unique combinations of performance, reliability, robustness and SWaP. This session considers clocks that offer an advantage over existing clocks with a form factor larger than chip-scale atomic clocks. Presentations may be on any type of advanced clock in their present or potential future form. Examples of these clocks include: hot and cold atom clocks, ion(s)/molecules clocks; microwave, terahertz and optical clocks, optical frequency combs, and cavity stabilized ultra-stable lasers; cryogenic sapphire oscillators; and optically pumped clocks.
Session Chairs:
Dr. Roberto Diener, ONR
Dr. Franklin Ascarrunz, Spectradynamics

Environmental Impacts on Clocks and Time Transfer
Clocks and time/frequency transfer systems are being used more commonly in uncontrolled environments like space or field test sites. As such, there is a greater need to understand the impact of thermal, magnetic, acceleration, radiative, or other environmental disturbances on these systems. This session will focus on studies that characterize or mitigate these impacts. This is timely as a newly updated version of the IEEE P1193 standard entitled “Guide for Measurement of Environmental Sensitivities of Frequency Standards” is being prepared for release. We invite submissions regarding this document and/or related aspects of studying environmental impacts on timing systems.
Session Chair:
Dr. Daphna Enzer, Jet Propulsion Laboratory

Low-SWaP Clocks and Oscillators for 5G and Beyond
Low-size, weight, and power (SWaP) clocks and oscillators are critical components for commercial and military applications. The telecom industry has moved towards tighter timing requirements on each antenna in the last decade. 5G requires microsecond absolute timing, and 6G+ will have even finer timing requirements, putting a premium on local clocks and oscillators. This future has a strong overlap with military timing needs, except the DoD clocks must operate and maintain timing through harsh environments including large temperature swings, high shock, and vibration. This session will discuss the state-of-the-art in low-SWaP, handheld clocks and oscillators, for DoD and telecom applications.
Session Chairs:
Dr. Jonathan Hoffman, DARPA
Dr. Jenna Chan, Army Research Laboratory

Mathematical Methods and Algorithms for Timing Applications
Mathematics and statistics play an important role in clock analysis and timing applications from the classical two-sample variance to advanced filtering techniques. This session seeks contributions on mathematical developments that help to analyze clock measurements, handle data anomalies, compute statistics around missing observations, generate timescales, and/or facilitate time transfer or dissemination. Algorithms presented can support any timing related activity from local oscillator performance to long range timing applications. All techniques are welcome although new and innovative approaches are of particular interest, such as those employing machine learning or artificial intelligence concepts.
Session Chair:
Dr. Michael Coleman, Naval Research Laboratory

Novel Methods in Time and Frequency Transfer
Precise timing is critical for operations including positioning and navigation, and timing for networks and communications. Despite its ubiquity and reliability, GNSS may not be available or provide the accuracy necessary.  Improved one-way free-space time transfer, and increasingly developed two-way time and frequency transfer are becoming more relevant in a world of dynamic PNT needs, utilizing both RF and optical time transfer. From two-way free-space microwave links to optical frequency combs with fiber links, this session will include presentations on the newest methods in the synchronization and syntonization of remote clocks in space, from space to ground, between ground stations, and potentially underwater.
Session Chairs:
Dr. Kari Moran, NIWC Pacific
Dr. Zachary Warren, The Aerospace Corporation

Present and Future Clocks for Space and Ground Stations
Abstracts are encouraged that consider the design, development and performance of clocks presently operating in space, or planned for near-term operation in space (LEO, MEO, GEO and deep-space).  Abstracts are encouraged that discuss next-generation space clocks.  For space, issues of Size, Weight and Power (SWaP), reliability, radiation hardening, and longevity are often more crucial for clock design than clocks solely aimed at terrestrial applications.  All types of space clocks are of interest: space-qualified crystal oscillators, warm-vapor lamp or laser optically-pumped clocks, cold-atom clocks, ion-clocks, optical lattice clocks, and any other clock technologies that can contribute to space-system timekeeping.
Session Chairs:
Dr. James Camparo, The Aerospace Corporation
Dr. Thejesh N. Bandi , The University of Alabama

Recent Innovations at Time Laboratories and National Metrology Institutes
This session will provide the opportunity for time and frequency laboratories, including those operated by national metrology institutes (NMIs), military, scientific and academic organizations, to highlight their innovations in PTTI sectors.  Compliant topics are related to UTC(k) generation and performance, time dissemination, time services, calibrations and specific PTTI measurements. Progress reports on primary frequency standards and optical clock contributions to TAI as secondary frequency standards, are welcome and encouraged.
Session Chairs:
Dr. Giancarlo Cerretto, INRIM
Roger Brown, NIST

Role of Clocks and Timing and How they Operate in Present and Future GNSS Architectures
Keeping time is the heart of any GNSS and it takes a complex system with elements in the control segment, onboard the satellite, and with the user equipment to maintain it. This session will focus on how both present and proposed GNSS maintain time and frequency to provide users with a robust navigation signal. Papers presenting both innovative concepts for architectures in LEO, MEO or Cis-Lunar as well as reviewing little known details of existing infrastructure are welcome. The session is especially interested in a diverse representation of timing solutions from GNSS around the world.
Session Chairs:
Dr. John Janis, L3-Harris
Dr. John Elgin, Air Force Research Laboratory

Time Transfer and PNT from Proliferated LEO Constellations
Satellite-based time transfer and navigation from Low Earth Orbit (LEO) has been considered for over a decade, but the advent of proliferated LEO (pLEO) systems now opens up the realization of an effective implementation. In pLEO systems, the production of low-cost small satellites, and the commensurate access to space allows the rapid formation of constellations numbering in the hundreds of space vehicles (SV). These architectures featuring meshed inter-satellite links, allow for the near immediate propagation of timing corrections to SV clocks, supported by two-way inter-satellite ranging. This also enables robust and resilient terrestrial and cislunar navigation. The session will capture the most recent work in using LEO for space-based time transfer and navigation. Both commercial and defense oriented space systems are welcome to submit papers. Key performance characteristics might include maintaining accuracy under periods when access to UTC is not available, either from GNSS, or space to ground links, and the anticipated precision in time transfer approaching ps stability. The session will also consider submissions discussing the evolution of pLEO systems to lunar applications.
Session Chairs:
Greg Weaver, JHU-APL/SDA
Chris Erickson, Space Force

Time Transfer Over Comms and Unconventional Methods
Traditional RF time transfer using point to point signals or one-way through GNSS use either a GNSS receiver or purpose-built time transfer modems. In this session we explore alternatives to traditional methods in the vein of the convergence between time and frequency transfer and existing communication systems; exploring existing or emerging communications systems and their cooperative or non-cooperative use for time and frequency transfer. In addition to timing over comms systems, we’re also interested in exploring submissions that cover unconventional means of transferring time and frequency using naturally occurring phenomenon or using non-traditional communication channels.
Session Chair:
Dr. Per Olof Hedekvist, RISE Research Institutes of Sweden

International Technical Meeting (ITM)

ITM Keynote Address

Dr. Han Park, Deputy CTO and Head of R&D at Hyundai Urban Air Mobility

ITM Sessions

Alternatives, Backups, Complements to GNSS
Recognizing the vulnerability of GNSS users to both natural threats and security vulnerabilities, this session will bring together a variety of topics and applications. This session is looking for contributions describing new positioning methods or technologies, navigation aids, terrestrial transmitters or pseudolites, as well as anything that would complement or replace GNSS during an outage situation. Other topics may include dealing with terrestrial multipath, impact of degenerate geometries on positioning, atmospheric distortions and integrity monitoring for terrestrial radionavigation. Papers can address any domain, including (but not limited to) aviation, maritime, transportation, railway, or space flight.
Session Chairs:
Dr. Okuary Osechas, German Aerospace Centre (DLR) 
Dr. Michael O'Connor, Satelles

Collaborative Navigation
Algorithms and methods of collaborative navigation for GNSS challenged and denied environments. Improvements in satellite availability via data exchange at the measurement level. Improved resilience of GNSS signal processing via multi-node signal accumulation and beamforming in collaborative acquisition and tracking. Applications of collaborative techniques to sensor-fusion with signals of opportunity (SOOP) and non-RF aiding (e.g., vision and lidar) of inertial systems.
Session Chairs:
Dr. Adam Rutkowski, Air Force Research Laboratory
Dr. Kirsten Strandjord, University of Minnesota

GNSS and Security: Interference, Jamming, and Spoofing
Techniques to make GNSS more robust to spoofing, jamming, and interference in general, through signal processing, complementary PNT, authentication, or other means. Applications in robust positioning and secure time transfer. Threat modeling, assessment, and mitigation. Analysis of GNSS disruption events.
Session Chairs:
Dr. Andriy Konovaltsev, German Aerospace Center (DLR)
Mathew Cosgrove, Northrop Grumman

GNSS Integrity and Augmentation
Fault monitoring, fault detection and exclusion, protection level algorithms and requirements for receiver-based integrity, ground-based, space-based, and aircraft-based augmentation. Challenges in the provision of integrity in multi- frequency/multi-constellation services. Applications include navigation for civil aviation, automotive, UAVs, rail, and maritime.
Session Chairs:
Dr. Santiago Perea , European Space Agency
Elisa Gallon, Illinois Institute of Technology

Radionavigation Beyond Medium Earth Orbit GNSS
Going beyond signals from Medium Earth Orbit (MEO) GNSS, this session examines alternate and novel radionavigation signals and techniques to support the demands of modern navigation systems. Signals of opportunity include cellular (e.g., LTE and 5G) and communications satellite signals (e.g., low Earth orbit (LEO) Mega Constellations), CubeSat and remote sensing satellite signals. Navigational aids include terrestrial ultra-wideband (UWB) technologies, modern Wi-Fi protocols, near-field communication (NFC) devices, and emerging LEO-based satellite time and location services. Precise orbit determination and clock estimation for opportunistic satellite-based PNT. Combining these sources to demonstrate PNT accuracy, integrity, and robustness, particularly for mission and safety-critical applications including automated vehicles (AVs) and intelligent transportation systems (ITS).
Session Chairs:
Dr. Kazuma Gunning, Xona Space Systems
Dr. Chun Yang, QuNav

Sensor-Fusion for GNSS-Challenged Navigation
Fusion of measurements from multiple sensors, data, and information sources for navigation in GNSS-challenged and denied environments. Estimation theories, algorithms, data processing techniques, test methods, and results of new implementations integrating diverse sensors such as GNSS, inertial sensors, odometers, magnetometers, radar, lidar, cameras, barometers, maps, signals of opportunity, infrared, ultrasound sensors, etc.
Session Chairs:
Ryan Dixon, Hexagon
Dr. Naser El-Sheimy, University of Calgary

Autonomous Navigation Applications
Advanced positioning and navigation algorithms for autonomous navigation. Use of novel sensors, sensor fusion, and signals of opportunity. Algorithms and methods for high-performance applications using low-cost sensors. Derivation of multi-sensor system navigation performance requirements. New approaches for dealing with delayed and out-of-sequence measurements. Sensor and measurement fault detection and exclusion.
Session Chairs:
Dr. Nikolay Mikhaylov, Robert Bosch Corp.
Laura Norman, Hexagon

Extraterrestrial Navigation
Navigation system design and implementation for extraterrestrial navigation.  Surface and near-surface navigation for the Earth’s moon, Mars, or other planets and moons.  Cis-lunar and trans-lunar navigation beyond the Earth’s geosynchronous belt.  Relative navigation near asteroids and comets.  Navigation technologies including GNSS or GNSS-equivalent, other RF signals, electro-optical systems, and global or local magnetic fields.
Session Chairs:
Dr. Edward LeMaster, Lockheed Martin
Dr. Grace Gao, Stanford University

Precise GNSS Positioning
New algorithms and methods for improving Precise Point Positioning (PPP), Real-Time Kinematic (RTK) and other precise positioning techniques (e.g., PPP-RTK, network-RTK, partial ambiguity resolution). Multi-constellation solutions using single-/multi-frequency geodetic and low-cost receivers/antennas, including smartphones. Developments on Integer Ambiguity Resolution (IAR). Interoperability of correction services with different user equipment. Robustness against multipath and other local effects.
Session Chairs:
Dr. Daniel Medina, German Aerospace Center (DLR)
Dr. Patrick Henkel, Technical University Munich

Receiver Design, Signal Processing, and Antennas
GNSS receiver signal processing techniques for improved resiliency in challenging environments including indoor, urban canyons, foliage, scintillation, high-dynamics and under interference. Improved acquisition and tracking sensitivity, robustness and accuracy. Mitigation of multipath and non-line of sight signals. Design and evaluation of GNSS antennas and antenna electronics.
Session Chairs:
Dr. Sanjeev Gunawardena, Air Force Institute of Technology
Dr. Yu-Hsuan Chen, Stanford University

Remote Sensing, Atmospheric Effects, and Space Weather
Modeling of ionospheric and tropospheric effects on GNSS navigation. Use of GNSS for remotely sensing the atmosphere and Earth’s surface. Scientific applications of GNSS.
Session Chairs:
Dr. Brian Breitsch, University of Colorado, Boulder
Dr. Anthea Coster, MIT Haystack Observatory

Safety-critical Applications of GNSS and Other Sensors
Navigation system design and analysis for safety-critical applications of GNSS and other sensors. Topics include integrity monitoring for filtered solutions, antenna and receiver hardware/software, data collection and analysis techniques including sorting and clustering, and development of statistical models for measurement and process noise for use in safety-critical navigation algorithms.
Session Chairs:
Dr. Charles Toth, The Ohio State University
Dr. Madeleine Naudeau, Air Force Research Laboratory