Update: Comments on SpaceX’s FCC response on using Starlink for PNT from Todd E. Humphreys, Professor of Aerospace Engineering and Director of the Wireless Networking and Communications Group (WNCG) and Radionavigation Laboratory, at the University of Texas at Austin.
“It’s great to see SpaceX publicly acknowledge their interest in providing PNT with Starlink. Back when we published our first paper on the Starlink signal structure, we made it clear there is great potential for Starlink to provide PNT in addition to broadband.
Elon Musk responded to the MIT Tech Review article we did with a tweet saying ‘Starlink can obviously offer far more robust positioning than GPS, as it will have ~1000X more satellites over time. Not all will have line of sight to users, but still >10X GPS & far stronger signal. Just not today’s problem.’
Now it looks like SpaceX has come around to viewing PNT as “today’s problem.” But what’s interesting about their recent comment is an emphasis on the L-band D2C signals for PNT rather than the Ku-band broadband signals. It’s not clear how many unique D2C satellites each phone will be able to pull observables from. If only one, then positioning results will be slow and not very accurate. If several, then it may rival GPS accuracy, provided that SpaceX gets the timing right.
At present, Starlink’s timing in the Ku band is so irregular that accurate pseudorange-based PNT is not possible, as we show in a recent paper under review. Our work on this has been funded by the DOT under CARMEN+ (led by Zak Kassas at OSU).
SpaceX has submitted reply comments to the FCC describing how its Starlink LEO satellite system currently provides and could further support positioning, navigation, and timing (PNT) services. The filing was submitted as part of the FCC’s ongoing Notice of Inquiry (NOI) into promoting resilient and diverse PNT capabilities across the United States.
FCC’s Initiative on PNT Resilience
The FCC’s NOI (WT Docket No. 25-110), titled “Promoting the Development of Positioning, Navigation, and Timing Technologies and Solutions,” seeks to explore technological solutions to bolster the robustness of PNT services. Recognizing the vulnerabilities of GPS to jamming and spoofing, the FCC is soliciting input on both space-based and terrestrial alternatives to ensure national security, public safety, and economic stability.
In its comments, SpaceX outlines several technical characteristics of the Starlink system that it argues are relevant to PNT applications:
Existing Timing and Positioning Capabilities
SpaceX states that Starlink terminals can currently provide nanosecond-level timing accuracy and meter-level positioning using time-of-arrival measurements from Starlink satellites. The company notes that its network supports applications requiring precise timing—such as cellular network synchronization—without relying on external GPS sources. Timing signals are derived from the LEO constellation and synchronized through the network’s broadband infrastructure.
Architecture and System Design
The filing emphasizes that the Starlink system is built around several features SpaceX considers relevant for robust PNT support:
- LEO Configuration: With thousands of satellites in low Earth orbit, the system offers global coverage and short signal travel times.
- Directional Antennas: SpaceX highlights the phased-array user terminals as an advantage for signal integrity and interference mitigation.
- End-to-End Encryption: According to the filing, this makes Starlink’s timing and positioning information less susceptible to spoofing or tampering.
SpaceX notes that Starlink is already in commercial use by a variety of customers and has been tested by U.S. military and civilian users in degraded GNSS environments. It states that Starlink’s capabilities are not hypothetical and have been demonstrated under real-world conditions.
Integration with a Layered PNT Framework
In response to the FCC’s interest in a “layered” approach to national PNT resilience, SpaceX positions Starlink as one of multiple complementary solutions. The company argues that diverse, independently operated systems—satellite- and terrestrial-based—can provide redundancy and reduce dependency on any single technology or spectrum band.
The filing also addresses concerns raised by other stakeholders who questioned whether Starlink qualifies as a PNT system. It reiterates that Starlink was developed independently of government funding and can scale rapidly through SpaceX’s vertically integrated manufacturing and launch model.
Spectrum Use
SpaceX confirms that Starlink operates in Ku- and Ka-band spectrum allocated for broadband services and is not proposing new spectrum allocations for PNT-specific use. It asserts that PNT functionality can be delivered within existing allocation.
