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Dawn approaches Ceres, From opnav images to first orbit
alk3997
post Feb 12 2015, 07:35 PM
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Dawn's main antenna appears to be facing towards Earth right now with no gentle thrusting from the engines. I'm assuming more data is coming down...

BTW, I still see the northern hemisphere as brighter and less contracted than the southern hemisphere. The southern hemispehere seems to be more cratered and more excavated. But, I'm sure that will all change when we get better views.

Andy
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algorithm
post Feb 12 2015, 07:44 PM
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QUOTE
If we weren't allowed to speculate than this forum would be quite a bit smaller!

Today makes the beginning of an exciting week for the Dawn mission. Like was explained a couple pages back, from today to the 19th, Ceres is going to triple in resolution.



Triple the resolution = one third speculation. Right!

Or is it, triple resolution = 3x speculation??

Maths was never my strong point! laugh.gif
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fredk
post Feb 12 2015, 09:00 PM
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I think it scales with the number of pixels. So triple the resolution means 9x the speculation! laugh.gif
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Gladstoner
post Feb 12 2015, 10:35 PM
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Or to paraphrase Thomas Edison, it's 1% resolution and 99% speculation. smile.gif
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TritonAntares
post Feb 12 2015, 10:39 PM
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QUOTE (volcanopele @ Feb 3 2015, 10:30 PM) *
OPNAV3 hasn't been acquired yet.
Imaging won't until later this evening, MST.
From looking at Celestia, the observations times are (keep in mind that these are just the dwell times, the actual time frame when images are actually being taken is likely shorter and in the middle of these times frames):

Footprint 1: 2015-035 02:13-07:21 UTC
Footprint 2 (centered on Ceres): 2015-035 07:30-10:47 UTC
Footprint 3: 2015-035 10:56-14:35 UTC

The HGA is pointed toward Earth between 2015-0a35 15:53-2015-036 07:44 UTC (again, it might not be downlinking that entire time)

Meanwhile any times of todays imaging session RC1 and transmission available?
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algorithm
post Feb 12 2015, 11:44 PM
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QUOTE
I think it scales with the number of pixels. So triple the resolution means 9x the speculation! laugh.gif



I'll drink to that!!
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Gerald
post Feb 13 2015, 02:44 AM
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While eagerly awaiting the new images, here another processing of the Ceres OpNav3 sequence pia19179-16.gif, animated, and as tiles:

-- some remote similarity to the DLR version.

Regarding surface reflectance:
Approximately describing Ceres' surface reflectance needs far more sophistication than a matte Lambertian description of an ellipsoid.
A modified Lambertian description of an ellipsoid with a reflectance of about (cos phi) ^(0.7) for phi the angle between ellipsoid surface normal and Sun resulted in the best - but not in a good approximation - (for gamma = 2.2) thus far.
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0101Morpheus
post Feb 13 2015, 04:17 AM
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Those are incredible.

It is nice that we can finally start studying a large ellipsoid besides Iapetus. And we don't know very much about Iapetus!
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vikingmars
post Feb 13 2015, 09:46 AM
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WOW ! WOW ! WOW ! Thanks a lot Gerald ! wheel.gif wheel.gif wheel.gif
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Habukaz
post Feb 13 2015, 11:59 AM
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Dawn is talking to the DSN now. So is Voyager 1, apparently.

http://eyes.nasa.gov/dsn/dsn.html


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belleraphon1
post Feb 13 2015, 12:02 PM
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Looks like DAWN downlink is in progress as of 06:57am EDT.

http://eyes.nasa.gov/dsn/dsn.html

What a week ahead coming... DAWN Ceres RC1 and navcams from Rosetta 6 km 67P/CG flyby!

Craig
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volcanopele
post Feb 13 2015, 03:08 PM
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QUOTE (TritonAntares @ Feb 12 2015, 03:39 PM) *
Meanwhile any times of todays imaging session RC1 and transmission available?

Sorry, I've been busy with Rhea that last couple of days. Here are those times

FC Stare at Ceres: Feb 12, 2015 07:22:00 - Feb 12, 2015 21:45:25 UTC
The HGA is pointed toward Earth between Feb 12, 2015 22:44:58 - Feb 13, 2015 17:44:22

So the spacecraft will begin its turn back toward its thrusting orientation in approximately 2 hours, 36 minutes from this post. Maybe images will show up today online, but my money is on Monday.


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TheAnt
post Feb 13 2015, 04:29 PM
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Yes most likely on Monday, the personell on the MaxPlanck institute should have left for the day at this hour now since it is Friday. But I could imagine one or two have hanged around for a first peek anyhow. That unless some of the NASA guys hijack an image or two (joking), I noted that Goldstone have taken over from Madrid for Dawn transmissions now.
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algorimancer
post Feb 13 2015, 07:52 PM
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QUOTE (Gerald @ Feb 12 2015, 08:44 PM) *
...another processing of the Ceres OpNav3 ...

Gerald, this is some really impressive processing you're doing. I hope you write-up your methodology some day, I would like to have an educated basis for doing something similar (though how many firsts like this will we have?). Really gives a sense that there has been some major resurfacing of the northern hemisphere extending well into the southern hemisphere, or alternatively that there is a remnant unsurfaced region in the southern hemisphere. I haven't had this much fun since Spirit & Opportunity landed smile.gif
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Bjorn Jonsson
post Feb 13 2015, 08:08 PM
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QUOTE (algorimancer @ Feb 13 2015, 07:52 PM) *
Really gives a sense that there has been some major resurfacing of the northern hemisphere extending well into the southern hemisphere, or alternatively that there is a remnant unsurfaced region in the southern hemisphere.

Craters are much more difficult to see in the northern hemisphere at this resolution due to the higher sun angle - I see no clear evidence of major resurfacing in the northern hemisphere. The biggest craters might be in the southern hemisphere though. What's happening will be revealed in the higher resolution images to come - waiting for the new RC1 images is remarkably difficult.
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