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New Horizons: Near Encounter Phase
elakdawalla
post Mar 11 2015, 01:49 AM
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The plans for the Near Encounter Phase of the New Horizons mission have been set in stone since 2009. This week the mission has posted a Playbook that describes all the data that is going to be returned from the Near Encounter Phase -- not only the timing and geometry, but also when it is going to be played back. I also posted an article today about the data that will be played back during the couple of weeks surrounding closest approach. Some of the things I learned while writing that article that are of interest to this forum:

- Not a lot of data is being returned right away (in fact, only 1% gets returned within a week of the flyby).
- After July 20, there will be a long dry spell of no images being returned until the browse data set starts coming down on September 16.
- There will not be much scope for image processing on the data that is being returned near the flyby. There are one or two pairs of images that you can use to make stereo; there are two mosaics; there is one MVIC image for which there is LORRI data returned near enough in time to do colorization.

So it's going to be awesome, but we're also going to have to be patient!

Here is my simulation, using Voyager data, of the LORRI data set that we can expect to have on the ground as of July 20.



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Mercure
post Mar 19 2015, 12:03 AM
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Thanks so much for this very informative chart. Is the entire New-Horizons-facing Pluto hemisphere expected to be documented at 0.4km/pix resolution?
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elakdawalla
post Mar 19 2015, 02:54 PM
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Not all of it; there is a 15-footprint mosaic that covers maybe 30% of the visible disk. It's on page 20 of the Playbook I linked to in my post.


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Mercure
post Mar 20 2015, 08:28 PM
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Thank you! - Your chart is an excellent overview of the visuals to expect. The playbook has all the info, but your graphic is more digestible for those of us with limited time due to real life constraits (i.e. job and toddlers :-)
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Jaro_in_Montreal
post Mar 21 2015, 08:32 AM
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That's interesting.....
So, what happens between the time of the 15 highest-rez photos from 77,298km range (p.20) and the time when lower-rez photos are taken before (254,072km range, p.17) and after (359,895km range, p.22) ?
I realize it's all done on July 14, but just how long does it take to get each of the 15 hi-rez photos? ....one might be tempted to think that a more complete hemispheric coverage could be had. Why not ? (Thnx)


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nprev
post Mar 21 2015, 08:45 AM
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Primarily because NH's downlink bit-rate at that distance will be around 1kb/sec. Also, imagery obviously won't be the only data coming down and the DSN is a finite resource set that can't be dedicated to NH alone.

Excellent (as always) relevant blog article by Emily here.



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jgoldader
post Mar 21 2015, 11:11 AM
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QUOTE (Jaro_in_Montreal @ Mar 21 2015, 03:32 AM) *
That's interesting.....
So, what happens between the time of the 15 highest-rez photos from 77,298km range (p.20) and the time when lower-rez photos are taken before (254,072km range, p.17) and after (359,895km range, p.22) ?
I realize it's all done on July 14, but just how long does it take to get each of the 15 hi-rez photos? ....one might be tempted to think that a more complete hemispheric coverage could be had. Why not ? (Thnx)


A couple of possibilities come to mind, but they all lead back to a mix of too little time and finite storage capacity, and lots of choices on how to spend them.

If you look at the last panel in the figure you attached, you can see that it would take about 3x as many images to cover the expected error ellipse to be sure of getting the whole planet, so 3x as much time and 3x as much data.

This flyby isn't just about imaging, and there are tradeoffs, and I bet the meeting where the 15 images were settled upon was "interesting." Spectroscopy and occultations are also on the list, and those are going to take time and data as well. Since NH has to turn the whole spacecraft to point the instruments, it's not possible to get useful data from all the instruments at the same time. And don't forget the satellites, we want data on those as well.

But my gut tells me it's probably the amount of storage available on the spacecraft that limits the number of images, in the end. Maybe John will chime in to give the real answer.

Jeff
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john_s
post Mar 21 2015, 02:45 PM
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The scarcest resource during the close approach period is time rather than data volume. The spacecraft is designed to do fast turns (up to 1.25 degree/sec) to observe as many targets as possible during the close approach period, but still, each mosaic repointing takes time to settle before we can be sure of a sharp image, time is needed to allocate the memory for recording each set of data, and so on. To answer the specific question, that 15-image Pluto mosaic takes about 20 minutes, and is preceded by Nix observations (hi-res imaging and our best infrared compositional map), and followed by our best infrared compositional map of Charon.

We do get most of the visible disk of Pluto at 0.3 km/pixel with our wide-angle camera MVIC near closest approach, and the whole disk at 0.46 km/pixel with MVIC ten minutes earlier- part of the purpose of that 15-image LORRI mosaic is to provide stereo coverage with the closer MVIC scans.

There were indeed many lively meetings to figure all this out, but they were almost never acrimonious- the entire science team understands the importance of the holistic view of the system that will be provided by all these wonderful overlapping data sets.

John
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Alan Stern
post Mar 21 2015, 03:54 PM
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QUOTE (john_s @ Mar 21 2015, 03:45 PM) *
The scarcest resource during the close approach period is time rather than data volume. The spacecraft is designed to do fast turns (up to 1.25 degree/sec) to observe as many targets as possible during the close approach period, but still, each mosaic repointing takes time to settle before we can be sure of a sharp image, time is needed to allocate the memory for recording each set of data, and so on. To answer the specific question, that 15-image Pluto mosaic takes about 20 minutes, and is preceded by Nix observations (hi-res imaging and our best infrared compositional map), and followed by our best infrared compositional map of Charon.

We do get most of the visible disk of Pluto at 0.3 km/pixel with our wide-angle camera MVIC near closest approach, and the whole disk at 0.46 km/pixel with MVIC ten minutes earlier- part of the purpose of that 15-image LORRI mosaic is to provide stereo coverage with the closer MVIC scans.

There were indeed many lively meetings to figure all this out, but they were almost never acrimonious- the entire science team understands the importance of the holistic view of the system that will be provided by all these wonderful overlapping data sets.

John



John is right, the NH sequence planning team for Pluto encounter was exceptionally collegial. The mapping he describes beats the NASA spec requirement for hemispheric mapping of 1 km by a healthy margin, and adds the high-res mosaic. We beat NASA spec for Pluto color mapping and composition mapping by healthy margins too. Amazing data sets are in store!
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jgoldader
post Mar 21 2015, 05:54 PM
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QUOTE (Alan Stern @ Mar 21 2015, 10:54 AM) *
John is right, the NH sequence planning team for Pluto encounter was exceptionally collegial. The mapping he describes beats the NASA spec requirement for hemispheric mapping of 1 km by a healthy margin, and adds the high-res mosaic. We beat NASA spec for Pluto color mapping and composition mapping by healthy margins too. Amazing data sets are in store!


Shows what I know! wink.gif

Thanks John and Alan!
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Decepticon
post Mar 21 2015, 06:35 PM
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Jaro where did you get that image from?
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Gerald
post Mar 21 2015, 06:40 PM
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Page 20 of the Observation Playbook.
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Alan Stern
post Mar 21 2015, 07:10 PM
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QUOTE (Gerald @ Mar 21 2015, 06:40 PM) *
Page 20 of the Observation Playbook.



One note, this is only one of several Observation Playbooks. Others will be posted later on approach, covering other instruments and disciplines beyond just surface mapping by LORRI and MVIC. Stay tuned...
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hendric
post Mar 21 2015, 10:52 PM
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QUOTE (Alan Stern @ Mar 21 2015, 02:10 PM) *
Stay tuned...


Thanks Alan for letting us "in the conference room!"


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Ian R
post Mar 22 2015, 04:45 AM
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Seconded!


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