Ahead of talks this autumn about #Rosetta, I've been reviewing some of my old presentations.
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Ahead of talks this autumn about #Rosetta, I've been reviewing some of my old presentations.
I found a lovely two-panel panorama of Comet 67P/C-G that Aster Cowart made back in 2016 & remembered I'd always wanted to remake it myself, to see if I could pull up some extra shadow detail.
Here's my take on that image from 5 October 2014 at 19km from the comet, starting from scratch with data from the PSA.
Credit: ESA/Rosetta/MPS for OSIRIS/Mark McCaughrean CC BY 4.0
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Mark McCaughreanreplied to Mark McCaughrean last edited by
The two original OSIRIS Narrow-Angle Camera images are:
N20241005T125921538ID4FF22
N20241005T131022562ID4FF22and from the timestamps, you can see that they were taken about 10 minutes apart.
In that time, Rosetta moved around the comet & the comet rotated, changing the perspective, so the two images don't really match. Thus this is a collage rather than a true panorama & if you look extremely carefully, you might see the join. The empty sky has been slightly extended on the left too.
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Mark McCaughreanreplied to Mark McCaughrean last edited by
Both images were taken through the OSIRIS F22 filter which is in the orange. Thus this is a monochrome picture & the slight blue-silver tone I've added is just for dramatic effect – it's not true colour.
I've also had to compress the data logarithmically to pull up the shadows in the cliffs – in the original images, the contrast is extreme between the sunlit parts of the comet & those parts illuminated dimly by light reflected off the surface.
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Mark McCaughreanreplied to Mark McCaughrean last edited by
The glow in the sky & between the cliffs is real – it's due to sunlight being scattered off the dust & ice particles in the comet's inner coma.
The comet was not particularly active at this point, about a month before the small probe Philae was dropped to the surface.
That was by design, to avoid outbursts from the comet which became significant a year later when the comet approached perihelion, its closest approach to the Sun.
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Mark McCaughreanreplied to Mark McCaughrean last edited by
For a sense of scale, the image covers roughly 1100 x 720 metres at the 19km from Rosetta, although obviously some bits of the roughly 4km wide comet are closer to the camera than others, making that approximate.
Thus those promontories on the skyline to the left are roughly 80 metres high above the pedestal they're on – that's a 20-25 story building, so fairly substantial.
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Mark McCaughreanreplied to Mark McCaughrean last edited by
For reference, here's the original two-panel panorama that Aster made & posted on Flickr in 2016: there are shadow details in there which can pulled up with processing & essentially what I've done is remake the panorama from scratch to reveal more of the dynamic range:
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Mark McCaughreanreplied to Mark McCaughrean last edited by
And if you're interested in knowing where on Comet 67P/C-G this is, I believe that the smoother Anubis region on the side of the large lobe of the comet is in the foreground, looking towards the rougher Seth region, "over the hill", & with the neck (Hapi) & chin (Maat) regions of the smaller lobe in the background.
Here's a view of Anubis from further out where you can recognise some of the features & some maps to orient yourself.
ESA Science & Technology - Anubis region on comet 67P/C-G - OSIRIS NAC
Anubis region on comet 67P/C-G - OSIRIS NAC
(sci.esa.int)
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Mark McCaughreanreplied to Mark McCaughrean last edited by
Finally, the original two-panel mosaic at full resolution is 3248 x 2044 pixels: I downsized it to 2048 x 1389 pixels for posting here, not least because Mastodon isn't exactly kind to images when it compresses them.
I'll put the original PNG on my Flickr account in PNG format for download under CC BY 4.0 copyright.
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Mark McCaughreanreplied to Mark McCaughrean last edited by
For the patient among you, here's the full-resolution uncompressed image on Flickr.
Just remember, it's licenced CC BY 4.0, so you can use it freely but must give credit as in the caption.