4 ms·

I dislike that the article doesn't even clearly answer its own question. The probe only records 8GB of data to one of two 8GB memory bank (one primary, one back

by mrb 11y ago

I dislike that the article doesn't even clearly answer its own question. The probe only records 8GB of data to one of two 8GB memory bank (one primary, one backup). Then the data is compressed and sent at either 2 kbit/s or 4 kbit/s (if they manage to get the higher speed working). By this math it should take either 12 or 6 months. Actually even less since the data is compressed. So why will it take 16 months?? Gizmodo needs better writers.

maaku 11y ago
Because redundancy in transmission? Also I would be very surprised if the the data is not already compressed.
CamperBob2 11y ago
One possibility might be DSN receiver availability. There are only three sites in the network, and they have several other missions to support.
aleph_naught 11y ago
the DSN (deep space network) is a shared resource under high contention---it is effectively used by every deep space mission from Voyager to MSL(via MRO relay). missions generally have a dsn rep that negotiates dsn tracks based on need. high priority events like MSL's EDL or spacecraft safing events generally take priority. i haven't looked into the specifics but it is unlikely that new horizons gets 24hr coverage for 12 months straight.
- logicallee 11y ago
  this totally makes sense - you should work for comcast!
  - simoncion 11y ago
    Given Comcast's reputation, it sounds like you're being insulting. Was this your intention? If it was, you should actually read about the DSN. It (like most things pertaining to extraterrestrial operation) is pretty damn cool.
    - jjtheblunt 11y ago
      I thought not meant to be insulting but hopeful comcast would then improve.
      - logicallee 11y ago
        neither, it was just a joke :) I mean that this is a great way to explain 2 kbit/s or 4 kbit/s (makes sense in context) and I was just joking that that's about as bad as Comcast's service sometimes... :) (And so with explanations that great he should be their PR guy...) I guess it didn't go over too well, but no worries! You miss 100% of shots you don't take...
- waterlesscloud 11y ago
  You can see what DSN is up to right now here- http://eyes.nasa.gov/dsn/dsn.html http://eyes.nasa.gov/dsn/dsn.html
ArikBe 11y ago
In the press conference shortly after the flyby, one of the staff (I can't remember her name) said that the speed depends on the position of the probe relative to the ground antenna. So not only is transmission not 24 hrs, but when the probe appears to be on the horizon, transmission speeds are slower.
- hga 11y ago
  Lately I've been checking out the real time reporting page for the DSN (http://eyes.nasa.gov/dsn/dsn.html http://eyes.nasa.gov/dsn/dsn.html), and frequently one of the three big dishes at Goldstone, Arizona, USA, Madrid, or Canberra is allocated to a satellite, but is not right then doing any communicating, presumably because it's waiting for the earth to turn enough to get line of sight. Right now New Horizons is downloading at 2.11 kbs to Canberra, the max with both amplifiers transmitting with opposite circular polarizations. For a bit of comparison, Rosetta is talking to Goldstone right now at 104.86 kbs, with a received power 3 orders of magnitude stronger. And Voyager 2, which doesn't have much to say, is still plugging away with a smaller Canberra antenna at 159 b/s, and a received power about that of New Horizons.
rootbear 11y ago
The downlink is actually 1kbps, with 2kbps optional, by using both amplifiers with opposite circular polarizations. But they can't use that trick all the time. A nice article with more technical details is at http://www.planetary.org/blogs/emily-lakdawalla/2015/01300800-talking-to-pluto-is-hard.html http://www.planetary.org/blogs/emily-lakdawalla/2015/0130080...
- dang 11y ago
  Ok, since the consensus in the thread is that the submitted article (http://gizmodo.com/why-itll-take-new-horizons-16-months-to-send-us-this-we-1717769317 http://gizmodo.com/why-itll-take-new-horizons-16-months-to-s...) wasn't very good, let's try switching to that one.
- mikeash 11y ago
  Great article. And for anyone who didn't see it, to call this mode "optional" is putting it extremely mildly: to get enough power to run both amplifiers at once, they have to shut down the spacecraft's guidance system (!) and keep it pointed at Earth by using the thrusters to spin it up like a top. And this whole crazy scheme was developed after launch.
- deleted 11y ago
  [deleted]
mgkimsal 11y ago
isn't the fact that the transmitter is going further away during those 6 or 12 months adding to the time as well? or do the distances travelled not have much of an impact over that time frame?
icw 11y ago
Forward error correction can add significant overhead. From the specification of the RF subsystem posted earlier (http://www.boulder.swri.edu/~tcase/NH%20RF%20Telecom%20Sys%20ID1369%20FINAL_Deboy.pdf http://www.boulder.swri.edu/~tcase/NH%20RF%20Telecom%20Sys%2...), 5/6 of the data returned is redundant.

by mrb 11y ago

maaku 11y ago

Because redundancy in transmission? Also I would be very surprised if the the data is not already compressed.

CamperBob2 11y ago

One possibility might be DSN receiver availability. There are only three sites in the network, and they have several other missions to support.

aleph_naught 11y ago

the DSN (deep space network) is a shared resource under high contention---it is effectively used by every deep space mission from Voyager to MSL(via MRO relay). missions generally have a dsn rep that negotiates dsn tracks based on need. high priority events like MSL's EDL or spacecraft safing events generally take priority. i haven't looked into the specifics but it is unlikely that new horizons gets 24hr coverage for 12 months straight.

logicallee 11y ago
this totally makes sense - you should work for comcast!
- simoncion 11y ago
  Given Comcast's reputation, it sounds like you're being insulting. Was this your intention? If it was, you should actually read about the DSN. It (like most things pertaining to extraterrestrial operation) is pretty damn cool.
  - jjtheblunt 11y ago
    I thought not meant to be insulting but hopeful comcast would then improve.
    - logicallee 11y ago
      neither, it was just a joke :) I mean that this is a great way to explain 2 kbit/s or 4 kbit/s (makes sense in context) and I was just joking that that's about as bad as Comcast's service sometimes... :) (And so with explanations that great he should be their PR guy...) I guess it didn't go over too well, but no worries! You miss 100% of shots you don't take...
waterlesscloud 11y ago
You can see what DSN is up to right now here- http://eyes.nasa.gov/dsn/dsn.html http://eyes.nasa.gov/dsn/dsn.html

ArikBe 11y ago

In the press conference shortly after the flyby, one of the staff (I can't remember her name) said that the speed depends on the position of the probe relative to the ground antenna. So not only is transmission not 24 hrs, but when the probe appears to be on the horizon, transmission speeds are slower.

hga 11y ago
Lately I've been checking out the real time reporting page for the DSN (http://eyes.nasa.gov/dsn/dsn.html http://eyes.nasa.gov/dsn/dsn.html), and frequently one of the three big dishes at Goldstone, Arizona, USA, Madrid, or Canberra is allocated to a satellite, but is not right then doing any communicating, presumably because it's waiting for the earth to turn enough to get line of sight. Right now New Horizons is downloading at 2.11 kbs to Canberra, the max with both amplifiers transmitting with opposite circular polarizations. For a bit of comparison, Rosetta is talking to Goldstone right now at 104.86 kbs, with a received power 3 orders of magnitude stronger. And Voyager 2, which doesn't have much to say, is still plugging away with a smaller Canberra antenna at 159 b/s, and a received power about that of New Horizons.

rootbear 11y ago

The downlink is actually 1kbps, with 2kbps optional, by using both amplifiers with opposite circular polarizations. But they can't use that trick all the time. A nice article with more technical details is at http://www.planetary.org/blogs/emily-lakdawalla/2015/01300800-talking-to-pluto-is-hard.html http://www.planetary.org/blogs/emily-lakdawalla/2015/0130080...

dang 11y ago
Ok, since the consensus in the thread is that the submitted article (http://gizmodo.com/why-itll-take-new-horizons-16-months-to-send-us-this-we-1717769317 http://gizmodo.com/why-itll-take-new-horizons-16-months-to-s...) wasn't very good, let's try switching to that one.
mikeash 11y ago
Great article. And for anyone who didn't see it, to call this mode "optional" is putting it extremely mildly: to get enough power to run both amplifiers at once, they have to shut down the spacecraft's guidance system (!) and keep it pointed at Earth by using the thrusters to spin it up like a top. And this whole crazy scheme was developed after launch.
deleted 11y ago
[deleted]

mgkimsal 11y ago

isn't the fact that the transmitter is going further away during those 6 or 12 months adding to the time as well? or do the distances travelled not have much of an impact over that time frame?

icw 11y ago

Forward error correction can add significant overhead. From the specification of the RF subsystem posted earlier (http://www.boulder.swri.edu/~tcase/NH%20RF%20Telecom%20Sys%20ID1369%20FINAL_Deboy.pdf http://www.boulder.swri.edu/~tcase/NH%20RF%20Telecom%20Sys%2...), 5/6 of the data returned is redundant.