It's faster than my work's connection!
You are joking but in 2003 I had to live with 6 kbps (yes SIX KILOBITS) at a time when my monopoly telco was advertising broadband speeds.
Mars to Earth at an average of 29 kbits/s
31–40 of 88 posts
Re: Mars to Earth at an average of 29 kbits/s
#32Does anyone know more about the architecture of this space radio network? For example does it use tcp/ip on top over radio or is it packet switched as with amateur packet radio?
Here's some publicly available technical information about how the DSN works:
http://eis.jpl.nasa.gov/deepspace/dsndocs/810-005/
Re: Mars to Earth at an average of 29 kbits/s
#33So 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)
470K bits == 58.75K bytes
(assuming 8-bit bytes)
Re: Mars to Earth at an average of 29 kbits/s
#34I'm wondering how do they prevent non-NASA entities from sending commands to the rover - are they using some sort of cryptographic signatures when sending the commands?
This kinda raises question. I for one would not use encryption just to maximize bandwith efficiency. Deep space program are no where close to being a tactical advantage over another country. I wouldn't see why someone would like to screw it up. On the other side, there's always a moron out there to crash the party. So even if I wouldn't use encryption, I wouldn't be surprised if they use it.
I for one would not use encryption just to maximize bandwith efficiency.
Encryption typically doesn't make messages longer.
Re: Mars to Earth at an average of 29 kbits/s
#35I'm wondering how do they prevent non-NASA entities from sending commands to the rover - are they using some sort of cryptographic signatures when sending the commands?
I'm not sure about Curiosity in particular, but I work in the space industry and can say that commands are normally timestamped and encrypted. The encryption stops someone from commanding the spacecraft, the timestamp stops someone from recording a transmission and resending it later.
Re: Mars to Earth at an average of 29 kbits/s
#36So 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)
Latency matters, too. Often all the data is necessary to make decisions so (for example) only immediately transmitting a limited subset of the data is not really an option.
It’s not like that rover is driving around autonomously. It has some autonomy, but it can’t decide what’s interesting and what’s not, what has to be investigated and what not.
Re: Mars to Earth at an average of 29 kbits/s
#37Re: Mars to Earth at an average of 29 kbits/s
#38So 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)
Timeliness is quite important. In order to plan where to go and what to do next you need results from what you've just done. Without that you're just fumbling around blind.
Re: Mars to Earth at an average of 29 kbits/s
#39So 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 is 225 million kilometers / the speed of light = 12.51 minutes.
Vast data barges, roaming the solar system, keeping everyone in sync....
Building an interplanetary Internet is going to be very, very fun.
On a related note, never underestimate the bandwidth of a truck filled with...
Well I was going to say blueray disks. But the cheapest I can find bluray disks are 3 cents per gigabyte. 3 TB harddrives are easily had at 5 cents per gigabyte. If the data only needs to go 60 miles, then 120 drives ($18,000) in a truck would get 1 TB/sec, or 8,000 mbps...
Ouch. I'll go with a megabit connection. Once upon a time that sort of thing worked for bulk data ;)
Re: Mars to Earth at an average of 29 kbits/s
#40So 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)
470K bits == 58.75K bytes (assuming 8-bit bytes)
you also need parity bits