SpaceX Starlink Can Provide Super GPS With a Software Modification

There is an arxiv paper “Fused Low-Earth-Orbit GNSS”, by Peter A. Iannucci and Todd E. Humphreys of the Radionavigation Laboratory, The University of Texas at Austin, that details how low-earth orbit satellites can be modified to provide super-precise GPS.

MIT Technology Review indicates that the system would be accurate to 70 centimeters. Simple software upgrades can modify Starlink’s satellites so existing communications abilities and existing GPS signals could provide position and navigation services. Each Starlink satellite uses algorithms that are rarely found in consumer products. Spacex Starlink satellites already calculate their own location to within a few centimeters.

Here is information from the Fused Low-Earth-Orbit GNSS paper.

Low-Earth-orbiting (LEO) satellites could provide a positioning, navigation, and timing (PNT) service far more robust to interference than traditional Global Navigation Satellite Systems (GNSS). Previous proposals for LEO PNT require dedicated spectrum and hardware: a transmitter, antenna, and atomic clock on board every broadband satellite. This paper proposes a high-performance, low-cost alternative which fuses the requirements of PNT service into the existing capabilities of the broadband satellite. A concept of operations for so-called fused LEO GNSS is presented and analyzed in terms of the economy of its use of constellation resources of transmitters, bandwidth, and time. This paper shows that continuous assured PNT service over ±60° latitude (covering 99.8% of the world’s population) with positioning performance exceeding traditional GNSS pseudoranging would cost less than 0.8% of downlink capacity for the largest of the new constellations, SpaceX’s Starlink.

Previous proposals targeted positioning precision on-par with traditional GNSS pseudoranging (on the order of 3 meters), fused LEO GNSS can improve on this by more than an order of magnitude. It also offers a significant anti-jam advantage over L-band hosted-payload solutions in terms of signal-to interference ratio, thus making it attractive as a means for delivering assured PNT (A-PNT).

How is this possible?

1. We can use the massive data bandwidth in each broadband satellite transmission burst for up-to-the instant orbit and clock products. If such zero-age-of-ephemeris products are available, then expensive atomic clocks in LEO may be eliminated.
2. We can access these orbit and clock products by performing precision orbit determination (POD) on-orbit using traditional GNSS in a multi-tier architecture. This eliminates extensive ground segment to observe satellite orbits.
3. Commercial broadband signals in K-band and Vband will have both high signal-to-noise-ratio (SNR) and large bandwidth. This greatly reduces receiver noise and multipath error in L-band GPS.

It is possible to build a (relatively) compact, highly-directional receiver phased array for an additional 30 dB of anti-jam performance.

SpaceX’s Starlink could provide continuous centimeter accurate GPS service to 99.8% of the world’s population would require reserving at most 0.8% of system downlink capacity, 0.36% of system energy capacity, and a tiny amount of uplink capacity. This provisioning scenario would also reserve 5.3% of the constellation’s capacity for beam-steering, leading to at most a 0.1 dB increase in maximum pointing loss.

No atomic clocks would be needed.
No extensive ground station infrastructure is needed.
The GPS precision can ten times more accurate to about 30 centimeters or even better.
A jam resistant receiving station can be built.

SOURCES- Arxiv Fused Low Orbit GNSS, MIT Technology Review
Written by Brian Wang,

16 thoughts on “SpaceX Starlink Can Provide Super GPS With a Software Modification”

  1. Starlink will surely cover all pieces of the world and reach every part of it. Now we don't have privacy even without such an Internet and what can happen if Starlink will be launched?

  2. So there is "Musk Time" and if GPS determines position by super precise time measurements, then the positions calculated by Musk's Starlinks will called "Musk Position". There maybe a lot of wishful position calculations in those results. 🙂

  3. Yep. The risky bet was reducing and eventually stop making Merlin engines in favor of the Raptors, and thus relying on first stage reuse to cover the gap on required thrusters/1st stages.

    I don't know how much of that plan they have actually implemented, though.

  4. It's not as though the starship was a sudden surprise that was forced on them. Starship was their plan, if they can't meet their schedule because of the stress of their own plan then they stuffed up.

  5. The starlink is low orbit so any debris at that height deorbits and burns up naturally.
    You might get a few hazardous years if they all start playing demolition derby with eachother, but it's not a long term problem.

  6. Probably they are feeling the strain of developing a huge new rocket with new features nobody has attempted before, while still maintaining a functional rocket launch company.

    Musk already mentioned in the past that developing Starship while relying on the partially reusable Falcon 9 was a risky bet.

    And it's likely they are reaching the limits of the launcher market at its current launch prices.

  7. Sounds like a good opportunity for a private entity to provide full-time clean-up services or a relaxation on salvage rights for any non-functional satellite. Either way, a growth business that may spur additional investment in launches/ orbital infrastructure.

  8. …and new mutterings and whisperings of a small-retail investor IPO in the next several months, likely with ongoing proof of cash-flow, etc. If you though buying Tesla 3 – 5 years ago had a stunning burst of growth potential (but you should be out now) — this will likely be similar.

  9. I don't see how, no one wants to create a Kessler Syndrome type situation. Only real way is to hack and de-orbit.

  10. This is basically a rehash of the proposals behind the UK using OneWeb as a GNSS alternative to Galileo, since they were kicked out of the secret/high performance version of Galileo due to Brexit. Since this is basically a software hack, any next generation megaconstellation can pull this off.

  11. Spacex is getting behind on starlink launches, aren't they? I seem to remember two per month were planned, but it's been around one per month. Of course, the paying customers take priority, but still, they haven't gotten a lot of new contracts, have they?

  12. This all helps power beaming, at least the efficiency if not the base physics. Knowing where everything is helps. Knowing what time it is helps.

  13. Yes. Starlink will become a critical asset for asserting ground and space dominance, and a motor of the country/world's economy.

    Another reason for the re-start of an anti-satellite arms race.

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