Rosetta Photographs Its Own Shadow On Comet 67P/C-G 21
mpicpp notes an image release from the European Space Agency showing the shadow of its Rosetta probe on the comet it's currently orbiting. The probe snapped the picture from a very low flyby — only six kilometers off the surface. The image has a resolution of 11cm/pixel.
The shadow is fuzzy and somewhat larger than Rosetta itself, measuring approximately 20 x 50 metres. If the Sun were a point source, the shadow would be sharp and almost exactly the same size as Rosetta (approximately 2 x 32 m). However, even at 347 million km from 67P/C-G on 14 February, the Sun appeared as a disc about 0.2 degrees across (about 2.3 times smaller than on Earth), resulting in a fuzzy “penumbra” around the spacecraft’s shadow on the surface. In this scenario and with Rosetta 6 km above the surface, the penumbra effect adds roughly 20 metres to the spacecraft’s dimensions, and which is cast onto the tilted surface of the comet.
This is becoming a new trend? (Score:3)
Between Curiosity and Rosetta we seem to be in an age of Space Selfies.
And they say that robots don't take after their creators....
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And they say that robots don't take after their creators....
...as long as they don't take off *after* their creators...
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If Philae had been running systemd, it wouldn't have crashed.
There is science here (Score:5, Interesting)
And for those who like science fiction... If any aliens are riding the Rosetta probe, they will have to duck while the picture is being taken.
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The sun is not a point source. This is the same reason you get 2 shadows during a solar eclipse. The umbra and penumbra. The probe is 6km above the surface and it's not big enough to completely block the sun at that range, hence the fuzzy shadow.
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Hmmm. While your explanation is unquestionably true, I don't think you quite understood what the poster was asking. His question is, I think, about the sharp shadows behind ridges on the surface, not the shadow of the vehicle itself.
I think his problem is an implicit assumption that if you drew a line from the center of the sun through the spacecraft, it would intersect the surface at a right angle. In that case you wouldn't expect cracks on the surface to display in such relief. However I believe that
Ice "boulders" visible in photo (Score:2)
What I notice in this photo (hi-res version [esa.int]) around the area of the shadow are the apparent shapes of the ice "boulders" that came together to form the comet in the first place. It reminds me of looking at chondrules in meteorites, that show the siliceous "hailstones" that formed as the planetary disc that would go on the form the planets cooled.
Does this mean 6 more weeks of winter ? (Score:1)
As per Groundhog Day ?
Does that mean (Score:3)
Six more weeks of winter? Brrr.
The important story is missing (Score:1)
WHAT KIND OF SHIRT WAS HE WEARING?
Because we can't move forward until we know this information. It's more important than anything the announcer said, that's for certain.
It saw its own shadow? So it means.... (Score:2, Troll)
6 more weeks of asteroid showers? (Score:2)
We're past groundhog day..
Philae (Score:1)
I can't remember... (Score:2)
Does this mean there will or won't be 4 more weeks of winter on the comet?