Item — HN Reader

It's all about latency. Having broadband with 200+ms of latency to reach geostationary satellites is to slow for modern networks.

https://www.satsig.net/latency.htm

You have to move the satellites closer to Earth to reduce latency - hence low earth orbit (LEO). You can achieve much better latencies, <20ms, and support modern networking applications.

https://arstechnica.com/information-technology/2020/03/musk-...

But when you reduce the height to LEO, not only are the satellites no longer geostationary, they also have a much smaller coverage area. So you need more satellites to cover the same area, and fancy networking to handle the constant hand-off between satellites.

3 comments

To grab a couple bits of info from that page + google, to give people a good idea of the distances involved at a glance:

    Starlink orbit:           550km
    Geosynchronous orbit:  35,786km
    Earth's circumference: 40,075km

Geosynchronous orbits are quite a way out. Latency at terrestrial distances can be painful already, bouncing through geosynchronous satellites will be multiples worse at a minimum. Meanwhile, Starlink's are at "normal" distances for networking - you probably connect to things further away all the time already.

The low latency is also a requirement to receive FCC subsidies related to rural broadband, e.g. see https://www.reddit.com/r/spacex/comments/h04on0/fcc_just_vot....

Have heard (IIRC in https://theamphour.com/518-satellites-and-evs-with-joris-aer...) that this could have been part of the reason for Starlink's decision to have their satellites in a lower orbit.

The subsidy angle is also of course a familiar playbook across SolarCity/Tesla/SpaceX etc.

Bandwidth as well. Starlink can reach 100Mbps, and they're talking about 200Mbps. They can do that in part because they have more satellites.

> because they have more satellites

I wouldn't characterize this as a function of having more satellites, but rather having fewer users per satellite (an admittedly subtle difference). But, related to the above post(s), the smaller geographical area each satellite covers is a problem for coverage (you need more satellites in orbit), but is a benefit for speed -- you have less users vying for the full bandwidth of the satellite.

And, because the geographical areas are smaller, instead of having one base station/uplink, you now have geographically distributed base stations, so you have multiple points to access the Internet. This also helps with bandwidth (instead of X total uplink capacity, you need X/n capacity for each site, where n is the number of sites).

Once you get around the logistics of managing a fleet of satellites, many, many benefits flow from having lower orbits.