AST needs more satellites for continuous US coverage

AST needs more satellites for continuous US coverage

Direct-to-device (D2D) satellites or "cell towers in space" can eliminate dead zones but the 45-60 satellites announced appear insufficient for 24/7 services across the US.

AST SpaceMobile aims to deliver broadband-like speeds directly to unmodified cellphones, a claim recently validated in a trial conducted with Vodafone . During the trial, a successful video call was made between Vodafone CEO Margherita Della Valle and researcher Rowan Chesmer via an AST BlueBird satellite, which was passing over a remote mountainous region in Wales, U.K., where Rowan was situated.

The BlueBird satellite’s advanced phased-array antenna, along with other innovations, enables broadband speeds to and from smartphones and satellites. However, as discussed in previous articles, the capabilities of individual LEO satellites alone are insufficient to ensure continuous coverage in areas not served by terrestrial wireless infrastructure.

This article examines AST's recent announcements regarding the number of satellites planned for the medium term and explores potential future scenarios to infer the commercial viability satellite count. The analysis leverages analytics from the Non-GEO Constellations Analysis Toolkit version 5.2 (NCAT 5.2).

Simulation scenarios

AST has publicly stated that with 45 to 60 satellites planned for launch in 2025 and 2026, the company expects to provide 24/7 coverage across the U.S. Additionally, in its Q3 2024 SEC Form 10-Q (page 33), AST mentioned that 20 Block-2 satellites, in conjunction with the existing Block-1 satellites, will deliver intermittent coverage to the most commercially attractive MNO markets, representing an initial "cash-flow" scenario. Thus, the following scenarios were simulated using NCAT:

  • “Bull” scenario with 60 Block-2 satellites orbiting at 732 km altitude
  • “Bear” scenario with 45 Block-1 satellites orbiting at 520 km altitude
  • “Cashflow” scenario with 20 Block-2 satellites orbiting at 732 km altitude.

Given AST's initial goal of providing continuous connectivity across the United States, the analysis concentrated on the latitude range of the Continental U.S. (CONUS), specifically considering smartphones located at the northernmost and southernmost points—Seattle, WA, and Miami, FL, respectively. While these locations are well-served by terrestrial wireless networks, the findings are also relevant to other regions at similar latitudes.

Propagation delay and link distance for AST Block-2 satellites. Source: NCAT5.2

AST has not yet disclosed which of the inclined-orbit shells will be populated first with Block-2 satellites. For simulation purposes, it was assumed that the satellites would be positioned in one of the three shells filed with the FCC, specifically the shell with a 40-degree inclination and an altitude of 732.5 kilometers. As with any simulation, the results are based on these assumptions. For example, if AST satellites could maintain a link at very low look angles and distances greater than 1,600 km (1,000 miles), the satellite footprint would be larger, improving the pass time and availability. NCAT users can conduct simulations under various conditions to assess alternative scenarios.

“Bull case”: 60 Block-2 satellites

Simulation assumptions:

  • 60 Block-2 satellites evenly distributed across 5 orbital planes (12 satellites per plane).
  • Satellites operate at an altitude of 732.5 km with an inclination of 40 degrees.
  • Smartphones connect with satellites that are in line of sight at an elevation angle of 20 degrees or higher above the horizon.

The 12-hour simulation, accelerated 300X within the NCAT framework, generates data with 1 to 2-second granularity, which is summarized in the histogram charts.

Simulation results:

Northern CONUS:

  • Service availability: 56% of the time
  • Wait time between satellite passes: up to 15 minutes (see histogram)
  • Service time for satellite passes: over 5 minutes generally (see histogram)

Southern CONUS:

  • Service availability: 87% of the time
  • Wait time between satellite passes: generally 1 to 5 minutes (see histogram)
  • Service time for satellite passes: over 5 minutes (see histogram).

AST wait and service time histograms for 60 satellites. Source: NCAT5.2

Data:

The NCAT data and analysis are available for download in Excel format (10MB).

Video:

“Bear case”: 45 Block-1 satellites

Simulation assumptions:

  • 45 Block-1 satellites evenly distributed across 5 orbital planes (9 satellites per plane).
  • Satellites operate at an altitude of 520 km with an inclination of 40 degrees.
  • Smartphones connect with satellites that are in line of sight at an elevation angle of 30 degrees or higher above the horizon.

The 12-hour simulation, accelerated 300X within the NCAT framework, generates data with 1-second granularity, summarized in the histogram charts.

Simulation results:

Northern CONUS:

  • Service availability: 40% of the time
  • Wait time between satellite passes: see histogram
  • Service time for satellite passes: see histogram

Southern CONUS:

  • Service availability: 15% of the time
  • Wait time between satellite passes: see histogram
  • Service time for satellite passes: see histogram.

AST wait and service time histograms for 45 satellites. Source: NCAT5.2

Data:

The NCAT data and analysis are available for download in Excel format (12MB)

Video:

“Cashflow case”: Assuming 20 Block 2 satellites

Simulation assumptions:

  • 20 Block-2 satellites evenly distributed across 5 orbital planes (4 satellites per plane).
  • Satellites operate at an altitude of 732 km with an inclination of 40 degrees.
  • Smartphones connect with satellites that are in line of sight at an elevation angle of 20 degrees or higher above the horizon.

The 12-hour simulation, accelerated 300X within the NCAT framework, generates data with 1-second granularity, summarized in the histogram charts.?

Simulation results:

Northern CONUS:

  • Service availability: 20% of the time
  • Wait time between satellite passes: see histogram
  • Service time for satellite passes: see histogram

Southern CONUS:

  • Service availability: 35% of the time
  • Wait time between satellite passes: see histogram
  • Service time for satellite passes: see histogram.

AST wait and service time histograms for 20 satellites. Source: NCAT5.2

Data:

The NCAT data and analysis are available for download in Excel format (15MB)

Video:

The long-term view: AST filing with the FCC

Launching all 243 satellites across the three shells outlined in the FCC filing would enable AST to offer global continuous coverage up to 63 degrees latitude north and south. However, for CONUS specifically, completing the 40-degree shell with 150 satellites would be sufficient to provide continuous coverage, according to NCAT.

AST SpaceMobile's 243-satellite constellation filed with the FCC. Source: NCAT5.2

Conclusions

The key takeaway from this analysis is that, under the specified conditions, 45-60 LEO satellites are inadequate for AST to deliver continuous CONUS coverage. Unlike messaging services that can tolerate minutes of wait time, broadband services demand consistently high levels of availability. As a result, AST will possibly need to begin managing market expectations regarding continuous coverage in the U.S. and other regions.

As previously described, LEO direct-to-device (D2D) is not a winner-take-all market due to the intricacies of the mobile value chain. However, it is still a scale-driven business with two technical-level interconnected factors that are crucial for success:

  • Satellite Power: The size and power of individual satellites, along with critical elements like frequency bands and orbital altitudes, dictate the types of services offered. The range of services—from texting and narrowband to broadband—is largely shaped by satellite power and the integration with Mobile Network Operators (MNOs), as smartphones have inherent power limitations that restrict service capabilities.
  • Satellite Count: The number and strategic distribution of satellites across orbits are essential for ensuring continuous coverage. A higher satellite count, along with the right orbital positioning, impacts the availability of satellites in line-of-sight, which is inherently variable and not fixed.

This article focused on the latter, while AST ranks highly on the former. However, finding the right balance between these two factors is crucial for AST and other constellation operators aiming to deliver reliable, broadband-like 24/7 services directly to smartphones in remote or underserved regions.


The Non-GEO Constellations Analysis Toolkit (NCAT) is an assembly of easy-to-use analytics models to assess and benchmark LEO and MEO satellite constellations. To learn more about NCAT:

Timothy Thorson

Physics graduate

3 天前

What if the sattelites are put into orbits that focus on keeping service continously to certain regions, such as North America, rather than being equally spaced across the earth?? Would that be feasible at 45 satelites and still provide intermittent service to most other areas of earth?

Insightful article I am confident ASTS and its partners know what they are doing.

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Kevin Chen, P.L.Eng., AScT

Project Consultant at Jensen Hughes Consulting Canada Ltd.

6 天前

Who paid for this report?

Fysal Gill

| Serial Entrepreneur & Investor | Strategic Leader & Innovation Driver | Board Member & Advisor |

1 周

Good point!

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Subhoraj Mukherjee

VSAT | RF | IoT | LTE/5G | NGSO | SCS

1 周

Another insightful article, as usual. Thanks for sharing. The key for AST here seems to be managing customer expectation, irrespective of whether they go with Bull, Bear or Cashflow scenario. None of the scenarios will meet 100% availability, which is something terrestrial customers are used to (in coverage zones). It will be interesting to see their strategy till 2027 (assuming Starlink D2C will be launching bulk of their satellites by then, fine tuning voice and data service).

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