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Mars to Earth at an average of 29 kbits/s

mars.jpl.nasa.gov

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Re: Mars to Earth at an average of 29 kbits/s

#61

Post by jeza »

rubberbandage wrote: post #44
keithpeter wrote: post #3

Earlier quoted context omitted.

Yes, the clue is in the comparison to 'home modems'. The technology was finalised 2004, which means design around 2000 or so? I'm impressed with the reception technology that allows 'direct to home' communication at all given the power levels available.

Absolutely, this seems like one of the most amazing in a long string of incredible things. There’s only enough energy to power two 60w light bulbs, and yet it can transmit all the way to earth while also powering the computer running the thing.

This probably has more to do with the massive antenna (also known as a radio telescope) here on earth that are used to pick up the signal. Fortunately a few such antenna exist around the globe, so Mars should be in view of one of these antennas at all times. According to Wikipedia (http://en.wikipedia.org/wiki/Deep_Space_Network), radio telescope complexes used by NASA are located at: Goldstone Deep Space Communications Complex near Barstow, California, USA Robledo de Chavela near Madrid, Spain Canberra Deep Space Communications Complex near Canberra, Australia

Re: Mars to Earth at an average of 29 kbits/s

#62

Post by 205guy »

There must be some amateur radio people out there able to receive these signals, no? With the protocol stacks mentioned in the other comments, I wonder if they're able to extract the encrypted data. Which leads me to think there have got to be people/governments trying to figure those out.

Re: Mars to Earth at an average of 29 kbits/s

#63

Post by ck2 »

The high gain system they have for curiosity has an upper end of 2Mbps - to the orbiter.

The orbiter can talk to earth at up to 6Mbps depending on how far away we are at that time.

6Mbps at that distance is a staggering feat of engineering.

Re: Mars to Earth at an average of 29 kbits/s

#64

Post by mkramlich »

eupharis wrote: post #39
ChuckMcM wrote: post #24

So one wonders at what point you uplink to a satellite with ejectable flash drives which, when full, detach, make a gravity sling shot pass to leave orbit and then burn for a rendezvous with earth 9 months later. If I did the math right a 1TB drive returned from Mars in 9 months would be an effective bandwidth of 470K bits per second (or 47K bytes per second)

While we are dreaming, it would be better to have said flash drive picked up by a spacestation, refueled in orbit, and shot back to Mars. Hmm. If storage continues to improve as fast as it has been, once the space infrastructure is there, this might be cost effective. We have a lot of data to send. In particular, we are going to need to have a local cache of the internet on Mars. At best, the average minimum latency…

> In particular, we are going to need to have a local cache of the internet on Mars.

I predict somewhere today at Google an engineer just got an idea for his 20% project. "Red Cache"

Re: Mars to Earth at an average of 29 kbits/s

#65

Post by eupharis »

mkramlich wrote: post #64
eupharis wrote: post #39

Earlier quoted context omitted.

While we are dreaming, it would be better to have said flash drive picked up by a spacestation, refueled in orbit, and shot back to Mars. Hmm. If storage continues to improve as fast as it has been, once the space infrastructure is there, this might be cost effective. We have a lot of data to send. In particular, we are going to need to have a local cache of the internet on Mars. At best, the average minimum latency…

> In particular, we are going to need to have a local cache of the internet on Mars. I predict somewhere today at Google an engineer just got an idea for his 20% project. "Red Cache"

I hope so. The trick would be, after there is a cache of the Internet on Mars, to only have to send the changes, not the whole Internet again.

Straight snapshots would probably be the only viable option though. And maybe make the policy, once a decade do a complete update. And every year, do "any webpage accessed by colonists in the past year will be updated. And the top 5-15% of webpages by popularity on Earth."

And during the year, the top 5% of webpages, and any webpage with specifically Mars relevant content would be updated "wirelessly."

The numbers would change constantly, depending on bandwidth and costs and whatnot. But the question "how to build the best asynchronous shadow Internet given such and such constraints" is fascinating.

Re: Mars to Earth at an average of 29 kbits/s

#67

Post by packetslave »

mkramlich wrote: post #64
eupharis wrote: post #39

Earlier quoted context omitted.

While we are dreaming, it would be better to have said flash drive picked up by a spacestation, refueled in orbit, and shot back to Mars. Hmm. If storage continues to improve as fast as it has been, once the space infrastructure is there, this might be cost effective. We have a lot of data to send. In particular, we are going to need to have a local cache of the internet on Mars. At best, the average minimum latency…

> In particular, we are going to need to have a local cache of the internet on Mars. I predict somewhere today at Google an engineer just got an idea for his 20% project. "Red Cache"

Perhaps, but I just got an idea for an interview question...

Re: Mars to Earth at an average of 29 kbits/s

#68

Post by TheAmazingIdiot »

rubberbandage wrote: post #44
keithpeter wrote: post #3

Earlier quoted context omitted.

Yes, the clue is in the comparison to 'home modems'. The technology was finalised 2004, which means design around 2000 or so? I'm impressed with the reception technology that allows 'direct to home' communication at all given the power levels available.

Absolutely, this seems like one of the most amazing in a long string of incredible things. There’s only enough energy to power two 60w light bulbs, and yet it can transmit all the way to earth while also powering the computer running the thing.

You'd be amazed what you can do just with a watt of radio power.

If a transmitter and a receiver is in space, what's the furthest distance the receiver can go away from and have a 1 watt signal still above the noise floor? Assume the transmitter is a perfect omnidirectional.

About 9200 miles.

Re: Mars to Earth at an average of 29 kbits/s

#69

Post by graue »

DanBC wrote: post #8

Using Sloppy to view websites gives a reasonable idea of how slow this is. ( http://www.dallaway.com/sloppy/ )

Very cool concept. Unfortunately, this only proxies the starting hostname and doesn't rewrite absolute URLs, so on most modern websites, image/CSS/JS resources (being served from subdomains or S3 etc.) will load unproxied and not get slowed down.

Re: Mars to Earth at an average of 29 kbits/s

#70

Post by sillysaurus »

darkstalker wrote: post #6

What's the latency of that data connection?

Round-trip latency is the time it takes a signal to travel from Earth to Mars and back.

As Mars and Earth orbit around the sun, their distance relative to each other is constantly changing. The minimum distance from Earth to Mars is 35,000,000 miles, and the maximum is 249,375,000 miles.

Since light travels at 670,000,000 miles per hour in a vaccuum, we can calculate the minimum and maximum round-trip latency:

  Minimum round-trip latency
  = (2 * 35,000,000 miles) / (670,000,000 miles per hour)
  = (0.167164 hours) * (60 hours per minute
  = 10.0299 minutes

  Maximum round-trip latency
  = (2 * 249,375,000 miles) / (670,000,000 miles per hour)
  = (0.744402 hours) * (60 hours per minute
  = 44.6642 minutes
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