
Mars to Earth at an average of 29 kbits/s - kghose
http://mars.jpl.nasa.gov/msl/mission/communicationwithearth/data/
======
ryusage
It's awesome that they've been involving the public so much in the details of
how the rover mission really works. I'd actually been wondering about this
exact question, since it seems to be one of the limiting factors for the
quality of images and such. From a physics standpoint, sending data is clearly
a lot more complicated than I'd previously assumed.

~~~
Achshar
> It's awesome that they've been involving the public so much in the details
> of how the rover mission really works.

It must be mission critical to spread awareness since their budget cuts are
getting worse and one way to correct that is to get people excited about space
exploration. They now put a considerable effort in PR, involving people in the
mission, sharing most of the information and making professional videos. And i
believe this is why we see twitter accounts of most astronomers, satellites,
rovers and other NASA properties. The NASA's ustream has been very popular
lately and they have presence on every major social network. And curiosity was
named after an essay written by a student in a competition organised by NASA
for school students.

~~~
hrayr
"And curiosity was named after an essay written by a student in a competition
organised by NASA for school students."

Nasa has been doing this for some time now, Sojourner[1], and MERs (Spirit &
Opportunity) have also been named by student competitions.

[1] <http://mars.jpl.nasa.gov/MPF/rover/name.html>

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ChuckMcM
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)

~~~
eupharis
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 ;)

~~~
mkramlich
> 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"

~~~
eupharis
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.

~~~
merlincorey
Did you know -- there are more ports on the internet than just 53 and 80?

\-- A message from your friendly local hacker wizard

------
Dylan16807
So those are the lander->earth and lander->sat speeds. How fast can the
satellites transmit to earth? If we somehow always had a sat in reach of the
lander, how much data would we be able to send?

Edit: Did the research. MRO's antenna can handle .5 to 4 megabits depending on
the distance between planets. Wow, having to wait for flybys is a huge
bottleneck.
[http://mars.jpl.nasa.gov/mro/mission/communications/commxban...](http://mars.jpl.nasa.gov/mro/mission/communications/commxband/)

~~~
zhoutong
I wonder if it's possible to launch an orbiter in Mars synchronous orbit.
That'll eliminate the bottleneck.

~~~
waterlesscloud
Wouldn't just a higher orbit achieve the same thing? You'd be in sight for
longer periods, right? Without locking you into a location the way synchronous
would.

The current orbiters are primarily for imaging, so it makes sense that they're
as low as possible. If you were always going to have several surface missions,
it might make sense to have higher orbiters primarily tasked with
communication relay.

~~~
danielweber
As someone explained to me on another thread, the orbiters they have now are
in polar orbits. A more equatorial orbit would create very frequent uplinks.

One thing is that they didn't know Gale Crater was where they were going to
land until pretty soon before launch. There were a number of other sites. And
if they chose one further from the equator, that satellite wouldn't
necessarily be in the right place.

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rwhitman
I read this the other day and found it interesting:
<http://en.wikipedia.org/wiki/Interplanetary_Internet>

Apparently NASA had plans for launching an orbiter specifically as an optical
communications hub for Mars but scrapped it in 2005:

 _"As of 2005, NASA has canceled plans to launch the Mars Telecommunications
Orbiter in September 2009; it had the goal of supporting future missions to
Mars and would have functioned as a possible first definitive Internet hub
around another planetary body. It would use optical communications using laser
beams for their lower ping rates than radiowaves."_

~~~
jk4930
Now it's ESA's turn to try it:
<http://www.esa.int/esaMI/ESOC/SEMM5IHWP0H_0.html>

(OT: Note the picture at the bottom, the astronaut is one of ours: Austrian
Space Forum, a private space R&D org.)

------
vladd
I'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?

~~~
lavezza
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.

~~~
alanh
So there’s basically a real Goldeneye key. And you could really use a
Goldeneye key duplicator before leaving Severneya!

------
bwr
I'm guessing there is a lot of data that never gets sent to earth. Do they
send thumbnails of the images to determine what is interesting? Is there a
software tool available that creates a thumbnail and then creates a copy of
the original image that is dependent on the thumbnail to be recreated. If you
can't tell I wasn't really sure how to word that last sentence. Basically,
less data would be required to transmit because you are only sending the data
required to reconstitute the real image. Depending on the size of the
thumbnail this might result in a negligible difference.

For example, a very naive implementation might create a thumbnail from every
pixel where x or y is odd and then when/if you want the original image you can
get the data required to put the image back together (it would be a similar
sized thumbnail but with the even pixels) For this naive approach the
thumbnail would likely be much larger than you want and would not help at all
:)

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nemilar
This may be a silly question, but I don't understand why the bandwidth is so
low. I understand the latency will be high, since you're limited by the speed
of light; but wouldn't you be able to get more bandwidth just by increasing
the spectrum of light used, as well as the baud of the transmitter/receiver?

~~~
accountoftheday
Even with optimal coding you are still limited by achievable signal over noise
due to the Shannon limit.

------
DanBC
Using Sloppy to view websites gives a reasonable idea of how slow this is.

(<http://www.dallaway.com/sloppy/>)

~~~
graue
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.

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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.

------
fsiefken
Does 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?

~~~
gchang
Here's some publicly available technical information about how the DSN works:
<http://eis.jpl.nasa.gov/deepspace/dsndocs/810-005/>

~~~
Irishsteve
Up in Sweden they have DTN's for reindeer farmers. A helicopter which brings
food supplies acts as the data transfer relay.

DTN book for anyone interested in the area.
<http://www.amazon.com/dp/1596930632>

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drumdance
A friend of mine used to work at JPL on transmissions from one of the older
explorers. Maybe Voyager?

Anyway, he compared the energy used to transmit from the probe to that of a
flower petal falling from a height of six feet.

------
darkstalker
What's the latency of that data connection?

~~~
dantotheman
The real question is if its has an IPv6 address yet or if its still stuck
using IPv4?

~~~
vitno
It doesn't use IP... it uses a protocol called CCSDS

------
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.

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kayoone
Nice, just like my first modem back in 1996. Now let me host a dedicated
QuakeWorld Server on Mars!

~~~
mistercow
You might find that the 1700 second round trip latency is a tad higher than
your modem in 1996.

------
bluesmoon
I love this statement (from the Preventing Busy Signals page): "The Deep Space
Network (DSN) communicates with nearly all spacecraft flying throughout our
solar system."

------
xfhai
My suggestion is a satellite going around the Sun between Earth and Mars, so
that there would be more visibility.

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oleyb
It's faster than my work's connection!

~~~
barking
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.

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Florin_Andrei
So, it's basically like dial-up back in the day.

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diminish
what if they open sourced all of their components on github..

