Dawn approaches Ceres, From opnav images to first orbit |
Dawn approaches Ceres, From opnav images to first orbit |
Jan 12 2015, 12:10 AM
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Solar System Cartographer Group: Members Posts: 10227 Joined: 5-April 05 From: Canada Member No.: 227 |
On Tuesday (two days from now, for visitors from the future), the first optical navigation image will be taken... hopefully we'll have it in our hands soon after that. So it's time for a new topic. Over the next few months we'll have progressively closer images and full orbit characterization sequences, no doubt including multispectral image sets.
A new world... This is a bit of reprocessing I have been doing with the Hubble images from a few years ago. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Mar 3 2015, 06:23 PM
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
It seems with every release we find something odd about the resolution of the images. I've compared the main bright spot image (PIA19185) from the previous release with frame one of the animation in the latest release. They're pretty clearly the same image, as you can see by comparing features near the terminator (that's why I've gamma tweaked these images).
However, the PIA18920 animation frame 1 is stretched vertically relative to PIA19185! For this gif, I've left PIA19185 alone (apart from gamma), but for PIA18920 frame 1 I've rotated 10 degrees, followed by a reduction in size to 90% (horizontally and vertically): Previously we thought PIA19185 was supersampled 2x, so my suspicion is that the new animation frames have been altered. You can see a circular masked region on the new animation frames, with black outside. My guess is there may be some connection: someone tried to mask (I can't imagine why) with a circle and noticed Ceres isn't a sphere, so stretched it! Anyway, this clearly means that anyone trying to create map projections from the images (Gerald, Phil) has to be careful. |
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