Slashdot Log In
Japan Launches "Super-Speed" Internet Satellite
Posted by
kdawson
on Sat Feb 23, 2008 05:20 PM
from the fiber-in-the-sky dept.
from the fiber-in-the-sky dept.
A number of readers wrote in about the launch this morning of a Japanese H-2A rocket carrying a Kizuna ("Winds") satellite into orbit. Kizuna is intended to provide "super high-speed data transmission" for Japan and Southeast Asia. The news stories on the launch, such as the AP's linked here, are short on technical detail. For example they say the satellite successfully achieved orbit 175 miles above the earth — hardly suitable for Internet communications to a specific area on the surface (remember Teledesic?). Reader nebulus4 provided a link to the Japan Aerospace Exploration Agency site with an illustration and a little more detail. Such as the fact that Kizuna is destined for geosync orbit, and that a 45-cm antenna will equip eventual users for 155 Mbps down / 6 Mbps up, whereas a 5-m antenna will allow enterprises and ISPs to tap into 1.2 Gbps down. Given the latency to geosync orbit, you probably wouldn't want to use Kizuna to play an online shooter.
Related Stories
This discussion has been archived.
No new comments can be posted.
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
In other news... (Score:4, Funny)
Re:In other news... (Score:4, Funny)
Re:In other news... (Score:4, Insightful)
You cannot be serious (Score:3, Insightful)
Re: (Score:3, Insightful)
Re: (Score:3, Informative)
Re: (Score:3, Informative)
Yup, if it weren't for the Kiwis we'
Geosynchronous Latency (Score:4, Insightful)
round trip = times 4 = 88,932 miles
speed of light (wave propagation) = 186,282 mi/sec
latency = 88,932 / 186,282 = 0.477 seconds (on top of regular network latency)
Curse you speed of light. You win again!
Re:Geosynchronous Latency (Score:5, Funny)
Except, possibly chess.
Re: (Score:3, Interesting)
The connection sucks for anything interactive
Except, possibly chess.
I know you were joking, but as an administrator on a chess server, I can tell you that people get pretty pissed off when lagging half a second. It's acceptable for playing long games, but most over-the-net chess games are 1 to 5 minutes per player per ga
Re: (Score:3, Informative)
Re: (Score:3, Interesting)
In any case, a Molniya orbit would only require three satellites for coverage, looks ideal for Japan as a nation, and the perigee can be as low as
Molniya orbits (Score:3, Insightful)
Problem is, a Molniya orbit requires three satellites for coverage at the apogee, which is at about the same altitude as the geos
175 miles (Score:5, Informative)
What happens when (not if) ... (Score:3, Insightful)
With all this reliance on satellite technology for GPS, communications, and weather prediction what happens when (not if) the sun hits a more active solar cycle eliminating all of these satellites in one fell swoop? We have become terribly dependent on satellite technology (that I agree is cool). However, there have been solar storms that would knock out all of our satellites in recent memory -- only we did not have any satellites up yet. Now the satellites are up and the next large solar storm is just lurking out there getting ready to strike.
As usual, beware any significant reliance on any one technology.
Kizuna = "Bonds" not "Winds" (Score:5, Informative)
Re: (Score:3, Informative)
Speed is not everything... (Score:3, Insightful)
For web surfing and stuff this can be somewhat compensated for by prefetching and caching to make it less noticable, but for VOIP or other realtime use the lag can be very very annoying to say the least and it reduces QOS and transfers in general. Especially for any kind of distributed networking, torrents or multiple file download, the lag can add up and result in service issues. A single lost packet can take a half second to report to the server and have resent as can a next-file request.
These are not insurmountable and you can still get okay internet use for general purpose stuff, but it is a big disadvantage which there is really nothing you can do anything about. The speed of light is fixed.
Satellites really shine in certain roles, especially broadcasting where you have point-to-multipoint distribution. They work very very well with one-way content or stuff that does not require dynamic two-way data exchanging. They also do pretty well for remote reporting. Satellites are not optimal for two way internet traffic. That's just the nature of the beast.
Re:Now featuring... (Score:4, Insightful)
I believe geosync orbit has a MINIMUM lightspeed latency of 119.4ms.
Not a fun starting point BEFORE collisions and noise.
Re: (Score:3, Informative)
Re:Now featuring... (Score:5, Insightful)
You have to multiply times four to get a useful figure. Latency is normally measured round trip. Hop up, hop down, return hop up, return hop down. Latency to geostationary orbit is half a second.
However, 175 miles up is NOT geostationary. Geostationary is 35,786 km up, give or take. The orbit is geosynchronous. That just means the orbital period is the same as the earth's rotation, so it returns to the same spot at the same time every day. It will NOT stay in the same place, however. They'll have to have several of these things in a similar orbit flying over periodically like we do for GPS satellites. It also means the round trip latency is about 3.76 msec (just less than a millisecond per hop), a heck of a lot shorter than half a second.
Re:Now featuring... (Score:5, Interesting)
From the JAXA site about Kizuna:
"Scheduled orbit: Geostationary orbit at 143 degrees East longitude and at an altitude of about 36,000 km"
It is, even though the summarizer slipped up a bit (technically the term is correct, but somewhat misleading), destined for geostationary orbit.
Re: (Score:3, Interesting)
First, the speed of light is slowed down by fibre optic cable, just as light is slowed travelling through any medium. Roughly light in optical fibre travels 2/3 the speed of light in a vacuum.
So, to compute minimum late
Re: (Score:3, Interesting)
The fact that you posted this racist crap in the first place or the fact that you posted anon so you could mod down anyone that responded to you.
Re:Latency? What latency? (Score:5, Insightful)
175 miles? Try more like 22,230 miles. That's pretty much the only place you can put it unless you want your internet connection to only work 3 minutes out of every 90 minutes...
The reasons are simple physics. Gravity causes everything to want to fall towards the center of the Earth. Satellites manage to stay in orbit because they are constantly "falling" ahead of the Earth. That's why things in "low earth orbit" are referred to as being "in freefall" and not REALLY in zero gravity. Gravity is still there, only the velocity of the satellite is so high that all gravity manages to do is curve the trajectory of the satellite, not cause it to lose height. This means your satellite is going to be moving VERY fast with respect to the ground.
It's only at 22,230 miles out where the circle is so big that your satellite now appears fixed with respect to the ground. It's still moving. It's still "free-falling". But it appears to be hovering over a fixed spot over the equator - very useful for communication satellites since now you know where to aim your antenna and you don't have to bother moving it.