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Interplanetary Network (IPN) Tested

Posted by michael on from the token-ring dept.

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.

7 of 138 comments (clear)

  1. Isn't that a bit early? by locknloll · · Score: 5, Interesting

    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...

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  2. I'm kind of surprised... by TWX · · Score: 4, Interesting

    ...that they haven't implemented some form of relay satellite over Mars already. I'd think that one satellite in space would remain viable longer than a ground craft, and since it's in space it wouldn't have the dust-on-the-solar-panels problem, the atmospheric barrier problem, or the temperature variance problem. The ground craft wouldn't need to be built to transmit to Earth, just to an orbiting Mars satellite, which would handle the rest, so the landing craft could have engineering to make it more suited to its task rather than concentrate on radioing home.

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    1. Re:I'm kind of surprised... by Skyshadow · · Score: 4, Interesting
      that they haven't implemented some form of relay satellite over Mars already.

      Well, they *are* using existing orbiters to communicate with the current generation of orbiters. You know, just like the headline there says.

      I suspect that before any serious Mars exploration ramps up, a set of satellites in martian geosync would be a good idea. Not only would that facilitate communiation with anything actually on the planet, but it could also provide for a global positioning system.

      The real issue up to this point is that we just haven't needed that sort of thing yet. If/when we send people (especially if we follow Zubrin's advice and send them for 500+ day stays, or my advice and just build a colony and get on with it), that will change. If nothing else, just increasing the amount of bits you can push by sending a constant stream of lower-power 1's and 0's to a satellite instead of screaming data at the DSN here on earth a few hours a day would probably be a big benefit to future missions.

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    2. Re:I'm kind of surprised... by I+don't+want+to+spen · · Score: 5, Interesting

      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.

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  3. Re:USATODAY.com for all your science needs... by AeroIllini · · Score: 5, Interesting

    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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  4. Not even that good. by Civil_Disobedient · · Score: 4, Interesting

    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 just to make matters worse, you've got to deal with some serious high-gain amplification to "dial them up". Beaming cable over a satellite's easy -- sending it millions of miles away means a lot more power (a scarce commodity on a satellite to begin with) or a much more sensitive antenna on the recieving end. I don't know what the current data transmission rates with the things we sent to Mars, but for reference, the Magellan probe back in the 90's had a transmission rate of 115 - 268.9 kilobits/sec.

    It is really amazing to consider that we now have a "spy" satellite orbitting Mars relaying images of the surface back to us on Earth, and that it's sensors are good enough to show us photos of the landing of the rover on the surface. Just incredible. But this technology is still in its infancy -- we've still got decades before we land a man on the planet. This is an amazing page about the Soviet exploration of Venus that may also be of interest.

    1. Re:Not even that good. by dvd_tude · · Score: 5, Interesting

      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.