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Interplanetary Network (IPN) Tested
CETS writes "Slim on detail but...USA Today reports of the first test of an Interplanetary Network. 'In a sign of cosmic communications to come, last week mission controllers sent signals to a Mars-orbiting European spacecraft, which relayed the instructions to NASA's Spirit rover on the surface, and a signal was returned to Earth back along the same path.'" NASA also has a press release.
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I mean, good intentions, and kudos to NASA to get that infrastructure up and running, but it will probably take some more years before this really starts to make sense.
I guess it won't be used for routing traffic to gameservers...
-- Power corrupts, but PowerPoint corrupts absolutely.
Does that come before or after pinging the Mons Venus?
I'm looking forward to the day we can slashdot a website on another planet.
SIG: TAKE OFF EVERY 'CAPTAIN'!!
No, Wesley. Now rub my bald head.
Do you like German cars?
get people excited about space exploration. I for one am overwellmed by the string of success. Heck .. I even have NASA TV constantly running on my computer just so I don't miss a press release and to lean more about the rovers. Previously we were limited to bot's being in a "Direct line of sight" with Earth to transmit data. Now with the IPN we can get data faster and more often. KUDO's to NASA and the ESA for great job !
USA Today, is right, though. The lag time between Earth and Mars is anywhere between 3 and 22 minutes when Earth and Mars are clostest and farthest away from each other in their orbits.
And I think NASA has had plans to incorporate signal relay satellites for some time. Of course, NASA plans to build many more probes/satellites than actually get launched, so we're just now seeing satellites with relay capabilities. There were plans as far back as 1997 to launch a series of satellites whose only purpose was to relay signals from other spacecraft. Interplanetary routers, if you will. However, due to budget cuts, the capability was instead built into satellites with otherwise scientific payloads.
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The IPN and the Internet are two different things.
The IPN does not use TCP or another transmission control protocol because it is simply not possible to acknowledge data/rerequest data if the latency is that big (minutes to days in the solar system).
Now I just hope that I remember to post this as AC ...
Geostationary orbit satellites only last about 10-15 years before the satellites run out of fuel. I don't know if a Martian equivalent would need more or less fuel due to the lower gravity. The current orbiters can also do useful planetary observation as well as acting as a communication relay, precisely because they do orbit over the planet's surface and can see the whole of it from close range. I doubt that 3 aerostationary, or whatever the correct Martian term is, satellites would adequately perform observations for their much higher orbit as well as providing blanket comms coverage for the planet. Plus power considerations etc. I'm sure it will happen, but not for a good while yet.
Don't go to a brothel if you want to buy broth
This will be the case for the next Orbiter (Mars Reconnaissance Orbiter 2005) and any others prior to the Mars Telecommunications Orbiter which has a primary objetive of being a proper telecoms relay. MTO will provide at least 10x the current bandwidth, communication windows up to 8 hours in duration and will use optical as well as S-Band\X-Band radio links.
You know, to prevent a Little Green Man-in-the-Middle Attack?
--Leo
They do have one thing that helps (as it turns out, quite a bit): no in-band background noise to interfere with the communication.
Anyway, yes their data rates are lower than diect broadcast TV satellite. It's all about the relative S/N owing to inverse square law and the greater distance to the deep space vehicle. The rover and orbiter link rates are on par with Magellan's - 128~256 kb/s, compared with about 30mb/s for a DTV satellite transponder channel.
Read this chapter in JPL's Space Flight Primer for more information about how their space vehicle comms work. A tidbit I found in there: they use coherent (phase-locked) transmission and Doppler to very accurately measure the remote vehicle's position. That's a neat hack.
Both things are amazing when you look at them, for different reasons. Deep space communication is amazing because it's possible. Direct broadcast satellite is amazing because it's so cheap!
A nitpick: the 'milestone' stated in the article, which was apparently overlooked by many of the posters here is the fact that, for the first time, a non-NASA spacecraft (in this case the ESA's Mars Express Orbiter) got into the act as a data relay for the rovers. This is more a statement about cooperation than it is about outright technical achievement. It is a political milestone, much the same as our (America's) cooperation with Russia in the ISS and in developing new rocket booster technology. Yet while it is political, it is a good thing in that it's another step toward recognizing that for space exploration to be fully realized it needs to be global endeavor, not a national one.
This is very much at odds with Bush's election-year 'man to the moon' pipe dream that serves no real scientific end and is more about beating the collective American wiener on the table with China.