MESSENGER News Thread, news, updates and discussion |
MESSENGER News Thread, news, updates and discussion |
Apr 20 2005, 11:22 AM
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#101
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Member Group: Members Posts: 562 Joined: 29-March 05 Member No.: 221 |
Launched on August 3rd 2004, NASA's MESSENGER will become the first spacecraft to orbit Mercury.
News and updates are availbale via Johns Hopkins University MESSENGER website and the Kennedy Space Center's MESSENGER website. There will be an earth flyby in August followed by a couple of swings by Venus and three velocity scrubbing passages past mecury before the craft enters orbit in March 2011. April 18, 2005 status report from JHU. Extensive JHU FAQs page here. |
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Nov 1 2006, 12:07 PM
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#102
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Rover Driver Group: Members Posts: 1015 Joined: 4-March 04 Member No.: 47 |
Here's the drawing. green and red show two objects at different distances. lines show middle and edges of field-of-view. If you have a projection plane perpendicular to the middle line at a distance c, a will not equal b for the two cases. Not sure this is how exactly they made the plot though.
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Nov 1 2006, 04:06 PM
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#103
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
I'm not sure I get that plot, but I understand what you're saying about the distances. However, I'm talking about the angle between Earth-Sun-Mercury, see how it changes in the two instances. That does look like a bug. I have a fair amount of experience playing around in Celestia/Orbiter and never have I encountered such position shifts, even for large FOVs. To drive my point further, here are two plots from the Solar System Simulator:
Earth centered Mercury centered If you disregard the rotation (the sim probably aligns to the target north axis), you can see how the angle stays the same and is consistent with the first screenshot I posted, viewing Earth. Earth stays on the same "side" of the Sun in both cases, as one would expect. -------------------- |
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Nov 1 2006, 05:17 PM
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#104
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Having a fairly extensive experience playing around with 3D software and even writing a 3D renderer myself I cannot see how this could be anything but a bug. The views are supposed to show the Earth and Mercury as seen from Messenger at the same time and therefore the same location. The field of view is identical (or at least very nearly so), judging from Mercury's distance in pixels from the Sun. However, not only is the Earth's location relative to the Sun different in the two images, its 'distance' is also different and that difference is big. The field of view also isn't very wide (~30°) so distortion isn't significant.
Assuming the views generated by the JPL Solar System Simulator are correct the view showing the Earth from Messenger is correct (or very nearly so) while the one showing Mercury is not. |
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