SpaceX is located at the Starlink Earth Station in Merrillland, Wisconsin. The company applied for a license for the station in September 2019, and the FCC approved the license in April 2020. Image: darkpenguin22/Reddit

In the process of competing with terrestrial broadband service providers for Starlink consumer terminal access to its 12GHz spectrum, SpaceX made important concessions to Kuiper Systems LLC (Amazon subsidiary) regarding its third proposed Starlink modification. Earlier this year, SpaceX asked the FCC to allow it to change the altitude, plane, and angle of its satellites. The company's commitment to customers depends to a large extent on this change.

Now, in a letter of commitment submitted by Mr. David Golman, the head of SpaceX satellite policy, the company acquiesced in Amazon's request to cancel some of the orbital overlaps between Starlink and Kuiper satellites and increase the distance between them. When this letter was released, Amazon raised safety concerns about its satellites in several meetings with the FCC.

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The concession is related to the Starlink cluster, which operates at an altitude of 570 kilometers and has 20 satellites on each of 36 orbital planes. SpaceX's request for modification requires the FCC to allow the company to reduce the height of the cluster by half from the early 1,300 kilometers. Part of the Amazon Kuiper constellation will operate at an altitude of 590 kilometers, and SpaceX's orbital tolerance allows the company to reduce or increase Starlink's altitude by 30 kilometers.

This ensures that when the Kuiper constellation is fully deployed (Amazon's 590 km cluster is the last cluster it will deploy), when SpaceX chooses to take advantage of this tolerance, SpaceX and Amazon's satellites will effectively share the same orbital shell. SpaceX's concession will now ensure that the maximum altitude of these satellites is 580 kilometers, which is one kilometer below the Kuiper Cluster's 9-kilometer orbital tolerance lower limit.

By granting Amazon concessions, SpaceX believes that the FCC should conditionally allow the company to deploy Starlink satellites in one of the two proposed polar crusts. This shell (the fifth column above) consists of 348 satellites, each group of 58 satellites orbiting six orbital planes. The company outlined the polar orbit launch window in December because it requires preliminary approval and believes that the shell will allow it to bring Starlink coverage to Alaska.

SpaceX has asked the FCC to allow it to test Starlink in Alaska, but the coverage in remote states is not the only reason behind the company's latest conditional approval request. In addition, Mr. Goldman believes that by introducing Starlink coverage into polar orbit, SpaceX will also target federal users to support critical missions in areas where satellite Internet access is the only option, thereby contributing to the national security of the United States.

However, while all this marks a big step in solving the Starlink problem in the FCC lobby, the most striking aspect of SpaceX's letter to the committee is its conclusion.

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Here, Mr. Goldman Sachs believes:

As a result of discussions with Amazon, SpaceX has now promised to accept Amazon’s terms of addressing its concerns. After solving the problem, SpaceX asked the committee to quickly approve its modification [emphasis added].

Although forward-looking, we will find below that this may not be the case.

Although SpaceX acknowledged the orbital height of an orbital shell, this concession is far from addressing all Amazon's concerns about the proposed Starlink modification. The company believes that the combination of the lower elevation angle of the Starlink ground station and the reduction in altitude and the doubling of the number of Starlink satellites will greatly increase the interference between the two constellations.

Amazon's data shows that when all three parameters are combined, the number of in-line interference events between Starlink and Kuiper increased by 250%. SpaceX’s proposed modification reduces the minimum earth station elevation angle from the previous 40° to 25°, because the company believes that this reduction will compensate for the reduction in satellite coverage due to the aforementioned reduction in altitude (lower satellites are broadcasting signals when Covers less ground).

Amazon’s analysis shows that in terms of coverage maps, if the proposed Starlink modification is allowed in its current form, its Kuiper constellation will face significant interference and potential coverage locations in North America.

Contrary to SpaceX’s assertion, it has decided that doubling the number of satellites in contact with the gateway earth station will not affect in-line interference. Therefore, the use of a more accurate metric will be all visible Starlink satellites. Amazon’s test shows that even in In this case, online events will still increase.

SpaceX also argued that because it is reducing the altitude of its orbit, the number of visible Starlink satellites will be reduced, thereby offsetting the effect of the decrease in inclination. Amazon's response is shown in the image in front of the gallery above, and the company shows how the reduced angle reduces the exclusive area where its satellites must communicate with ground equipment.

Finally, Amazon also believes that changes to the Starlink satellite antennas will greatly increase the beam profile they produce. Although the performance impact this may have on consumer download and upload speeds is the subject of another debate, Amazon believes that this will make the separation of earth stations and avoid interference as a strategy ineffective, and co-location (sharing) is still the only viable option. The selection allows the operator to operate without failure.

However, Amazon failed to acknowledge SpaceX's argument that a lower elevation angle would reduce PFD (power, flux, and density), so it ended up cutting the separation angle shown in the chart in the second slide above in half. This effectively throws out the company's argument that Starlink's modification will eventually greatly increase interference outside the park. The only change we get in the latest file is a rough statement claiming:

It is a conservative assumption to use the same separation angle threshold for the front and rear, because the reduction in SpaceX's height will increase the necessary separation angle.

However, without mentioning PFD, the statement indicates that Amazon may need to do more work in this area. As far as SpaceX is concerned, it did not mention any changes to the Starlink antenna design, which makes us wonder whether the company is aware of the changes that will occur in the non-geostationary fixed satellite service (NGSO FSS) environment.

Obviously, by establishing a regular launch cadence, SpaceX has ensured the existence of Starlink. Unless Amazon compares or beats the company in this regard, the arguments it makes to the FCC may still be classified as assertions aimed at delaying existing services. SpaceX's plan to quickly launch hardware in space has also aroused concerns among terrestrial broadband service providers-this is another service that has not yet been deployed.

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