New Horizons at Pluto

DGM said:
Question about that site. I'm confused by what direction the signal appears to be going. It seems that Canberra is sending signals (up signal). Am I just not understanding this correctly?
Click to expand...

When I first looked it looked like it was receiving. They may be sending back an acknowledgment? I don't know for sure.
 
One Skunk Todd said:
When I first looked it looked like it was receiving. They may be sending back an acknowledgment? I don't know for sure.
Click to expand...
In the lower left corner they show details on "up signal" or "down signal". I've only seen "up" (could be wrong). If they are just sending a wake up call (so to speak), The reply would be ~9 hours from now, right?

Like I said. I'm new to that site but I am now looking into it deeper. This brings me back to watching the NASA launches as a kid in the 60's. :)
 
New Horizon should be in collection mode right now -- assuming all is well. It will turn to communicate with the DSN in roughly 5 hours and that signal should be received roughly 9 hours 11 minutes from now. Canberra may be sending some pre-scripted command sequence to fit in to that timeline.
 
Ziggurat said:
This stuff is really common in communications and data storage (CD's and hard drives all use data correction algorithms), and there's a large body of mathematical work describing optimal efficiencies versus expected error rates, etc. NASA will undoubtedly be using error correction in their communications, but it's probably standard off-the-shelf stuff, because this data isn't "sensitive" in the way that military communications might be.
Click to expand...

Yes, and the decoders for these can both accept and produce probabilities for each bit (soft decision), which is really useful for satellite communications as you generally have a certainty associated with each bit as you receive it. Various types of decoders are then wrapped to provide the desired error correction strength and properties. They get very very close to the shannon limit.

https://en.wikipedia.org/wiki/Noisy-channel_coding_theorem

As many deep space probes do, new horizons uses what is known as a "Turbo code"

http://www.boulder.swri.edu/~tcase/NH RF Telecom Sys ID1369 FINAL_Deboy.pdf

https://en.wikipedia.org/wiki/Turbo_code
 
Gawdzilla Sama said:
I was suggesting that it would be captured by Pluto's gravity. It would have to slow considerably for that to happen, and that would have meant a longer trip with a "turn-over" somewhere near half way. Just curious as to how much time that would add to the trip.
Click to expand...

This mission was optimized for viewing in ~10 years (in case there are big changes and the atmosphere freezes out in the next few years). With that constraint, the speed on arrival is way too high to remove.

The "low-fuel" option to stay would be to *just* arrive at the target with almost no extra speed and use a tiny bit of thruster to enter orbit. The time to do that from the sun is equal to half the orbit period. For Pluto, that would be a one-way trip time of more than 100 years. The more fuel you carry to kill the speed at target, the more time you can shave off that.

If the planets lined up perfectly, you could probably do something where you took a fast trajectory to Neptune, then used it to slow down a final leg to Pluto, leaving it slow enough to enter orbit. But I'd imagine that you'd still need a fair bit of fuel for deceleration and probably more than 15 years.
 
One Skunk Todd said:
Also, the antenna on New Horizons is not steerable, so the whole spacecraft has to be turned to transmit, which means you're no longer collecting data. So you've got to balance the two, and right now at closest approach it's heavily skewed toward data collection, with bulk transmission later after there's not much to look at.*



*Until they reach the further KBOs, but that's a while from now. :)
Click to expand...



Ok, Ok ... I get it already!!

Just tell me when the thumbnails will be available on iTunes so I can go through the RAW pics and choose the ones I want NASA to convert to Hi-Res for me!
 
You must log in or register to reply here.

Back
Top Bottom