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Expert Opinions: The effect of LEO constellations on GNSS services

February 20, 2017  - By
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Q: What is the potential for low-Earth orbit constellations to augment services provided by the four medium-Earth orbit GNSS?

Doug Taggart, President, Overlook Systems Technologies, Inc.

Doug Taggart, President, Overlook Systems Technologies, Inc.

A: With more than one hundred GNSS satellites broadcasting on three or more frequencies, our international constellation of medium-Earth orbiting (MEO) satellites will provide a combination of path diversity and frequency diversity. However, satellites in low-Earth orbit (LEO) should be added to our MEO mélange to provide orbital diversity and thus cyber safety. The LEO satellites would have 20 dB less path loss and compel jammers and spoofers to become conspicuous. Even with only one LEO in view, we would be able to use the LEO signal as a hot clock to improve the robustness of GNSS signal acquisition by our users. For timing applications, a solitary LEO satellite would enable time transfer to fixed locations worldwide.


Per Enge, Professor and Director, Stanford university Center for Position Navigation and Time

Per Enge, Professor and Director, Stanford university Center for Position Navigation and Time

A: While it is prudent to take advantage of multiple PNT sources, the devil is in the details. Are users seeking more availability, accuracy, integrity and/or resilience to fill gaps? What is the complexity and cost for integration in user equipment, the reliability compared to other augmentations, the applications to be supported, vulnerability to interference, and so on? Additionally, all things from space may not be the best solution when all user needs and vulnerabilities are factored in.

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