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Philae landing on the nucleus of Comet 67P C-G
vikingmars
post Sep 23 2014, 12:16 PM
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Attached Image


Now, it's time to open a new section devoted to the landing of the Philae lander itself on the nucleus of Comet 67P C-G.

Also to answer better the earlier post,
http://www.unmannedspaceflight.com/index.p...st&p=212943
and for your information, here is the quick summary (as a "pdf" file) of the events that are expected to occur during landing on the nucleus and after : it's the timeschedule on which we are working to set up our EPO event in Paris.
Attached File  Sequence_ATTERRISSAGE10_UMSF.pdf ( 263.81K ) Number of downloads: 1475

The landing itself should occur around November 11th.

We'll keep you informed smile.gif
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SpaceScout
post Sep 23 2014, 02:14 PM
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Great information, thank you!!
ROLIS will take nadir images all the way down from the separation to landing and I am sure the images will be of high scientific values, but as I am reading in the document, the images will be uplinked to Rosetta only after touchdown. Was there no way to transmit the images as quickly as possible, without waiting for the landing?


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Phil Stooke
post Sep 23 2014, 02:41 PM
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The idea of transmitting images during the descent has been considered before, even as far back as the Surveyor landings on the Moon, and including Phoenix on Mars (actually, Phoenix MARDI images were not to be transmitted live, just transferred into the flight computer, and even that was too much of a risk).
Every time it has been abandoned because of the number and complexity of other operations at the same time.

Phil


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vikingmars
post Sep 23 2014, 03:40 PM
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QUOTE (SpaceScout @ Sep 23 2014, 04:14 PM) *
Great information, thank you!!
ROLIS will take nadir images all the way down from the separation to landing and I am sure the images will be of high scientific values, but as I am reading in the document, the images will be uplinked to Rosetta only after touchdown. Was there no way to transmit the images as quickly as possible, without waiting for the landing?

Dear SpaceScout, thank you for your kind comments.
Considering the great involvement of Germany in this mission, I should have put the timeschedule in German also, but my writing with Goethe's style is somewhat shaky : all my apologizes !
Yes, Phil is right : ESA does not want to interefere through the instructions with the transmitting of data during the landing phase. Sorry : so we will have to wait for the ROLIS images after a safe landing on the nucleus.
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Phil Stooke
post Sep 23 2014, 04:44 PM
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I just realized that I forgot about Chang'E 3 in my comments above. We did have spectacular video of the descent and landing. But I realized - I don't know if that was transmitted during or after landing.

Phil


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Explorer1
post Sep 23 2014, 05:51 PM
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I think it was halfway; I recall the streamed images were received at a much lower rate then the final landing movie; either only some were released on the live stream or only some were transmitted during the sequence.
Ok, found it:
Here is the live stream recording:
https://www.youtube.com/watch?v=jyg56VIKRNA
And the 'complete' video:
https://www.youtube.com/watch?v=XNAGFTRvgDY

To not derail too far; what will be sent from Philae during the descent if not images; there will be some telemetry?
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SpaceScout
post Sep 23 2014, 06:00 PM
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QUOTE (Phil Stooke @ Sep 23 2014, 04:41 PM) *
Every time it has been abandoned because of the number and complexity of other operations at the same time.

If I am getting this right, is the high number of processes that the computer needs to handle during descent (although is free fall) that prevent transmitting images ? Will Philae transmit live any telemetry at all to Rosetta before touchdown?
I am just thinking about the improvements that could be made for a next generation landing probe... rolleyes.gif


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MarsInMyLifetime
post Sep 23 2014, 06:15 PM
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QUOTE (SpaceScout @ Sep 23 2014, 12:00 PM) *
If I am getting this right, is the high number of processes that the computer needs to handle during descent (although is free fall) that prevent transmitting images ? Will Philae transmit live any telemetry at all to Rosetta before touchdown?
I am just thinking about the improvements that could be made for a next generation landing probe... rolleyes.gif

This is an interesting paper on the original conceptual design of Philae--from 1997! (just to remind ourselves of the era for which available stable technologies were being considered, and what incredible now-stable things might be in a next-gen lander)

http://www.open.ac.uk/personalpages/a.j.ba...ine/capcom.html

No descent imaging was even described in that paper, so the present capability and operational plan is a privilege, considering. Whole careers go by in the course of one such mission!


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djellison
post Sep 23 2014, 06:47 PM
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I don't believe they'll be taking a lot of descent images....indeed, there's not much point. OSIRIS resolution will out-perform that of the descent imaging until we're pretty close to the surface. One before bettering OSIRIS res , one at some intermediate point, one just before touch-down.....that would be enough for a very good localization.
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vikingmars
post Sep 23 2014, 08:29 PM
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QUOTE (djellison @ Sep 23 2014, 08:47 PM) *
I don't believe they'll be taking a lot of descent images....indeed, there's not much point. OSIRIS resolution will out-perform that of the descent imaging until we're pretty close to the surface .../...

Yes, Doug : indeed ! OSIRIS has a far better resolution than ROLIS from orbit.
This is why ROLIS will take just a few images during the descent. BUT at a low altitude (i.e. tens of meters from the surface) and until touchdown, it will start taking one image every 5 seconds...
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machi
post Sep 23 2014, 10:04 PM
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Original plan was (and it looks still is) to take few images after release from Rosetta and then few images before landing.
"Few" means up to 8 images.



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Tom Tamlyn
post Sep 24 2014, 03:21 AM
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QUOTE (Phil Stooke @ Sep 23 2014, 10:41 AM) *
The idea of transmitting images during the descent has been considered before, even as far back as the Surveyor landings on the Moon, and including Phoenix on Mars (actually, Phoenix MARDI images were not to be transmitted live, just transferred into the flight computer, and even that was too much of a risk).
Every time it has been abandoned because of the number and complexity of other operations at the same time.

Phil


The Ranger moon spacecraft perforce transmitted images during descent, because there wasn't any afterwards, but I can't think of any others. Well, maybe NEAR, if you call the whole approach a descent because the spacecraft eventually touched down, but that would be whimsical.

Can't think of any others, but of course I don't have the encyclopaedic recall of the two Dougs.

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Hungry4info
post Sep 24 2014, 03:42 AM
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MSL did a whole descent movie. MER did a couple descent images if I recall right.
Edit: Nevermind. The discussion was about transmitting them during descent rather than storing and transmission later.


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Explorer1
post Sep 24 2014, 03:47 AM
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And don't forget Huygens!
It's true that discussing why Huygens transmitted pictures on the way down and Philae won't is comparing apples and oranges (one had atmospheric observations as the primary objective with landing as a bonus, while the other is exclusively a lander), but there is a precedent of descent imaging from ESA.
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Hungry4info
post Sep 24 2014, 03:51 AM
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QUOTE (Explorer1 @ Sep 23 2014, 10:47 PM) *
...there is a precedent of descent imaging from ESA.

Was there anything similar planned for Beagle 2?


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