I also love this photograph, but it makes me wonder - does the Philae lander camera have a flash? The sunlight on the comet is shining from 'down' yet the Rosetta panels are lit from directly 'in front'. I suppose they might well need artificial lighting to take photos once (if) they land on the comet, but I don't think I've ever seen a probe photo taken with flash before! Anyone know?
The Rosetta probe has woken up ...
- Thread starter GlennB
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I also love this photograph, but it makes me wonder - does the Philae lander camera have a flash? The sunlight on the comet is shining from 'down' yet the Rosetta panels are lit from directly 'in front'. I suppose they might well need artificial lighting to take photos once (if) they land on the comet, but I don't think I've ever seen a probe photo taken with flash before! Anyone know?
Monketi Ghost
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I wonder if the surface gravity is even. I kind of doubt it.
One can try to calculate it.
Use some approximation of the comet's shape, assume that it has constant density, then integrate over it. A 3D version of the trapezoidal rule should suffice -- make a 3D grid and then estimate how much of the comet is in each grid cell.
Pixel42
Schrödinger's cat
Monketi Ghost
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I'm excited and still curious about the surface gravity and if there's a chance of a good landing.
Sockor
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Reading about shooting the harpoons: https://www.mps.mpg.de/3086295/Philae-Blog
They shoot with explosives, not rockets, in space. They have taken recoil in microgravity into account, right?
They shoot with explosives, not rockets, in space. They have taken recoil in microgravity into account, right?
Olowkow
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I'm far from an expert on any of this, but if they got this far I'm pretty sure they thought of recoil [F=MA]. I think gravity or lack of it would have little to do with recoil, just the trajectories. The problem would be if the harpoon were a significant mass with respect to the mass of the probe firing it. If the masses were equal, the Philae and the harpoon would take off in opposite directions at equal speeds when the explosive charge propelling the harpoon occurs.
I haven't found any figures on their masses, but I would guess that the harpoon mass compared to the Philae is quite small, which would reduce the effects of recoil. And the harpoon acceleration mentioned is not terribly great--tens of meters per second--not like a naval line gun. Also, IIRC there is plenty of fuel to permit engineers to compensate for the position change caused by recoil.
HighRiser
Graduate Poster
Let's hope all the different contractors are using the same units this time, too. "Oh... You wanted to propel a five kilo mass at twelve meters per second."
a_unique_person
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Is it supposed to be landing now?
thedopefishlives
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Next month.
Pixel42
Schrödinger's cat
Olowkow
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Olowkow
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5 days 20 hours 25 minutes to touchdown at [URL="http://en.wikipedia.org/wiki/Agilkia_Island"]Agilkia. [/URL]
Rosetta will deploy Philae on November 11 at 11:35 PM PST. Confirmation of the landing will arrive at ground stations around 8:03 AM PST.
Rosetta will deploy Philae on November 11 at 11:35 PM PST. Confirmation of the landing will arrive at ground stations around 8:03 AM PST.
Thanks again for the update. Fingers crossed.davefoc
Philosopher
Has the density been determined yet?
Can you tell us about the paper you were a co-author of?
ETA: I got interested in the density question a few months ago when initial estimates suggested a density much less than water. I thought that was interesting. Was it because a low density frozen gas was a major component of the comet? Was it because the comet had voids on the inside? My guess was that it was because the estimates were wrong. It seems like by now they should know what the density is.
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Much of the comet's original volatile content may be gone by now, leaving behind a spongy mass of dust grains.
But in addition to measuring the comet's mass with its gravity, it ought to be possible to measure its mass distribution's departure from sphericity. That ought to have been possible in Rosetta's 10-km orbits. It's 2D instead of 3D info, but it will enable testing hypotheses about the comet's mass distribution, like how depleted its outer layers are.
But in addition to measuring the comet's mass with its gravity, it ought to be possible to measure its mass distribution's departure from sphericity. That ought to have been possible in Rosetta's 10-km orbits. It's 2D instead of 3D info, but it will enable testing hypotheses about the comet's mass distribution, like how depleted its outer layers are.
It'd be a shame if we broke it.