The National Academies Logo
Research Associateship Programs
Fellowships Office
Policy and Global Affairs

Participating Agencies - AFRL

  Sign InPrintable View

Opportunity at Air Force Research Laboratory (AFRL)

Relativistic Time Synchronization for Satellite Crosslinks

Location

Space Vehicles Directorate, RV/Space and Planetary Sciences

RO# Location
13.40.01.C0064 Kirtland Air Force Base, NM 871175776

Advisers

Name E-mail Phone
Pham, Khanh Dai khanh.pham.1@us.af.mil 505.846.4823

Description

With an outlook towards flexible Global Positioning System (GPS)-surrogate technologies, this research opportunity focuses on time transfer and synchronization approaches for satellite constellations equipped with crosslink capabilities. Specifically, scientific breakthroughs are needed for time signals of onboard clocks to be transferred and synchronized through crosslinks, including gravitational effects such as Shapiro delays. The endpoints of these crosslinks are satellites with clocks in orbital motions (e.g., moving at 3 km per second for Geo-synchronous Orbits and 7 km per second for Low Earth Orbits). What follow are some technical challenges of interest, including (1) modeling, simulation, and analysis of relativistic time transfers in radio and/or optical clocks; (2) compensation of Shapiro delays and other propagation effects; (3) distributed time transfer mechanisms in radio and/or optical crosslinks; (4) stability and consensus in remote time dissemination; and (5) accurate processing of crosslink data for time synchronization accuracy and convergence.

 

References

Pham KD: “Stochastic Power Controls for Distributed Pulse-Coupled Synchronization”. IEEE Aerospace Conference, doi: 10.1109/AERO.2017.7943841, Big Sky, MT, 2017

Kirchner D: “Two-Way Time Transfer via Communication Satellites”. Proceedings of IEEE 79(7): 983-990, 1991

Miller J, et al: “NASA Architecture for Solar System Time Distribution”. Proceedings of IEEE Frequency Control Symposium: 1299-1303, 2007

Xie Y: “Relativistic Time Transfer for Inter-satellite Links”. Frontiers in Astronomy and Space Sciences 3: 2016

 

Keywords:
GPS denied; Time synchronization; Distributed time transfer; Onboard processing; Crosslinks; Shapiro delay; Synchronization accuracy; Propagation effects;

Eligibility

Citizenship:  Open to U.S. citizens
Level:  Open to Postdoctoral and Senior applicants
Copyright © 2014. National Academy of Sciences. All rights reserved. 500 Fifth St. N.W., Washington, D.C. 20001.
Terms of Use and Privacy Statement.