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Mars Orbiter Photographs another Mars Orbiter
rde writes "We're all familiar with blurry photographs of UFOs, but NASA have gone one better; the Mars Global Surveyor has photographed fellow satellite Mars Odyssey as it whizzed past. This is the first instance of one extraterrestrial satellite photographing another."
Can someone explain to me why the Odyssey appears twice in the image? I can't for the life of me figure it out, and the explanation they posted really isn't helping.
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My understanding of optics isn't too good. Isn't this the kind of thing where you trade amazing resolution for something else? Does this camera require massive amounts of light? Would it work when photographing something not directly reflecing the light of the sun, such as on the night side of Mars?
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This is infact tougher than it seems. Both satellites are on a polar orbit and at different speeds. And the camera on the MGS rotates as it takes pictures over this. Pretty awesome for the sheer mathematical probabilites involved
For sheer probabilites, imagine the Voyager out there in the beyond. It would be nothing short of a miracle to be spotted by a satellite from another planet.
Unless of course it bumps into the dear old gluttonous friend of ours from Trall!!
It's amazing what they've been able to get MOC to do...I can't wait to see what HiRiSe can accomplish! I'll be working with Mars Odyssey imagery in grad school next year and this image will make a fine addition to my cubicle.
It aught to be like passing one of those old handheld scanners back and forth over the same image. You'd get two mirror reflected images.
I smell a hoax! :) (Puts on tinfoil hat)
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OK, a purist may say that the moon lander does not qualify as a satellite, but I beg to differ here.
It should be a mirror image, providing the aspect of the object hasn't changed between the two passes across the image.
Think of the picture a graph, the vertical axis being in space and the the horizontal being in time. The camera is spinning, so the bit of space it's looking at is moving, but the thing it's photograping is moving too. As the diagram on the NASA site explains, the object first overtakes the spinning camera, then as it moves further away and it's apparent speed slows, the camera overtakes it again.
Imagine you're on the motorway, looking out of the the side window as a truck overtakes you. First thing you see is the front, then the back of it as it goes past. It slows down and you pass it - first thing you see is the back, then the finally the front. This is why you'd expect the two images to be mirrored wrt each other.
But, if the object is rotating as well (and in fact at closest approach you'd be seeing it from the side while the further away it goes the more you'd be seeing it from behind so in the frame of reference of the camera it is rotating even if it's not rotating wrt to the ground below it) then the aspect could change and cancel out the expected mirroring.
The fact that the apparent length of the boom on the side relative to the height of the craft changes between the pictures suggests that the the craft probably has rotated, but it would have to have done so by enough that the boom appears to be on the _other_ side of the craft to account for the image. Tin hat brigade, over to you...
Wonder if Martian scientists will one day be looking for signs of prehistoric life on Earth, contemplating terraforming, writing scifi, etc...
Assume I was drunk when I posted this.
Google Map shows a snapshoot of... swamp gas? Weather balloon? UFO?
http://maps.google.com/maps?q=airport&ll=33.647046 ,-84.411231&sll=33.748889,-84.388056&spn=0.006341, 0.007864&sspn=1.154297,1.855359&t=k&hl=en
Find the MD-80 taking off (runway 8R). Keep scrolling right, and you'll see the same airplane every 3/4 mile or so.