This is probably a stupid thing to ask, but: Could this setup be hacked to provide a loose form of GPS?
SpaceX just got FCC approval to launch 7,518 satellites
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Re: SpaceX just got FCC approval to launch 7,518 satellites
#42Does anyone have any context on what sort of internet speeds satellite internet has been benchmarked to provide. I can't imagine the latency being anywhere near good enough to do many of the high bandwidth things people use the internet for today.
Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming you…
SpaceX released a video about a week ago estimating that SF-London times were be around 60 ms, IIRC.
Re: SpaceX just got FCC approval to launch 7,518 satellites
#43Earlier quoted context omitted.
I live in Bolivia, South America, the impact a global ISP would have cannot be overstated, in developing countries internet prices are still extremely expensive, up until a month ago I was paying around USD 60 for 10Mbps, and that was the best price I could find in my city, the second largest in the country.
Yep, same here (Brazil). I suppose SpaceX plans to start with us-only offerings. I also suppose it will take a while until it reaches developing countries. Does anyone have a better take on this?
The satellites are not stationary, but go around the earth. This means that to get good coverage in the US, they actually have to provide good coverage everywhere near the same latitudes (on both sides of the equator). Since the satellites in the southern hemisphere will have nothing better to do and have less demand, they are probably going to start rolling out service everywhere they can at the same time.
Most of Brazil is actually a bit out of luck in that it's too near the equator, so satellite density overhead will not be that great anywhere but the very southernmost areas until there are lot of the birds in the sky, so you won't have service immediately. But places like Chile and Argentina will have great access pretty quickly.
However, as a caveat to that the receiving antennas will be expensive at the start and SpaceX still has to negotiate access to spectrum in every country separately, and in poorer countries this will most likely have to be paid for, so that will hike the prices up.
Re: SpaceX just got FCC approval to launch 7,518 satellites
#44This is probably a stupid thing to ask, but: Could this setup be hacked to provide a loose form of GPS?
Not stupid. Sort of. The term you're looking for multilateration (edit: i'm twisting the term a bit for my own use here, it's not exactly multilateration but it's not exactly triangulation either). Without looking at the RF specd in the FCC docs or the satellite hardware part list, I'm not sure if you could do it on the receiver, but it would be straightforward for the constellation visible to the receiver to triangulate a receiver's position and provide it over a maintenance channel to the terminal.
Re: SpaceX just got FCC approval to launch 7,518 satellites
#45This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move. But these are going to be moving and changing all the t…
With about a thousand being in your horizon at any given time I don't think it'll be an issue to roam between them. In a Metropolitan area it's not rare to be around dozens of cell sites. Likewise cellular roaming is quite transparent.
Re: SpaceX just got FCC approval to launch 7,518 satellites
#46This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move. But these are going to be moving and changing all the t…
>> Think about switching your router every 10 minutes.
Your cell phone switches towers all the time while you're on the road. My cellphone (republic) switches from WiFi to cellular network mid-call if I'm on it when I leave a building. This is not a new problem.
Re: SpaceX just got FCC approval to launch 7,518 satellites
#47According to Bloomberg, since there are currently fewer than 2,000 operating satellites, SpaceX’s new additions will dominate space.
This number surprised me, much lower than I expected. Looked it up and I'm seeing varying numbers, but generally in the 1k-4k ballpark.
Re: SpaceX just got FCC approval to launch 7,518 satellites
#48Earlier quoted context omitted.
Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming you…
> Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming yo…
The latency from the distance light travels does not vary that much. The rest of the ~600 ms latency is caused by the same thing as latency on ground systems (routers, etc.). And the processors on spacecraft are not particularly fast.
Re: SpaceX just got FCC approval to launch 7,518 satellites
#49This is probably a stupid thing to ask, but: Could this setup be hacked to provide a loose form of GPS?
You need more than just any satellites to provide GPS. Each of them needs a very precise atomic clock (among other things I'm sure I'm not aware of).
Re: SpaceX just got FCC approval to launch 7,518 satellites
#50This is probably a stupid thing to ask, but: Could this setup be hacked to provide a loose form of GPS?
Not stupid. Sort of. The term you're looking for multilateration (edit: i'm twisting the term a bit for my own use here, it's not exactly multilateration but it's not exactly triangulation either). Without looking at the RF specd in the FCC docs or the satellite hardware part list, I'm not sure if you could do it on the receiver, but it would be straightforward for the constellation visible to the receiver to triangu…
The answer is probably yes, but it would be a side-effect since data transmission will be the primary purpose. Actually it may turn out to be pre-condition for getting the best throughput - i.e. knowing when and where the sats are and when your transmission window is to within a tight tolerance will be necessary and that's what you need for GPS.