Comment by lxgr
3 days ago
That would still only require a couple dozens or few hundreds of satellites. For example, Iridium has 60-70, and Globalstar has less than 50 or so.
The actual reason for these new megaconstellations having so many is spatial frequency reuse through directional transmission/reception beams: More satellites means less users competing for each satellite's spectrum-limited bandwidth.
Iridium offers lower bandwidth and much larger cells than Starlink. But yes, the number of customers within a cell is also key to why there are so many Starlink satellites. Suburban (let alone urban) population density can easily consume the bandwidth available through one satellite.
Smaller spot beams are still technically possible for an Iridium-like constellation with fewer satellites. That's what e.g. ASTS is doing.
In fact, more than one (or maybe two, for geometric reasons near the equator where polar orbits are sparse etc.) satellite concurrently visible is pointless if the ground station/mobile device isn't also heavily directional, which is not the case for small, quickly moving handheld devices at least.
One other reason for wanting more satellites splitting footprint coverage between them would be if the satellite transmitters were transmit power limited.