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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."
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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Holy shit! How'd that swampgas get to Mars?!
We now have confirmed reports from an informed Orange County minister that Ethel is still an active communist.
They're one happy family, going on trips to exotic places and taking pictures of each other!
I guess that would a be near miss... no, a near hit... wait a minute... it's a near miss...
The two views of Mars Odyssey in this image were acquired a little under 7.5 seconds apart as Odyssey receded from a close flyby of Mars Global Surveyor. The geometry of the flyby (see Figure 1) and the camera's way of acquiring an image line-by-line resulted in the two views of Odyssey in the same frame. The first view (right) was taken when Odyssey was about 90 kilometers (56 miles) from Global Surveyor and moving more rapidly than Global Surveyor was rotating, as seen from Global Surveyor. A few seconds later, Odyssey was farther away -- about 135 kilometers (84 miles) -- and appeared to be moving more slowly. In this second view of Odyssey (left), the Mars Orbiter Camera's field-of-view overtook Odyssey.
Its the same frame exposed twice. Think about what happens when you take a picture, but set the exposure time too long.
They read their imaging array one line at a time. It saw the Odyssey once, which is the image you see on the left (I think). It continued to move, and then caught it again on the right. For the complete logistics of how it happened, we'd have to know more about their imaging array, and the relative speeds. Ya, I'd think there should be a blur in there somewhere, but aparently there isn't.
Think of a flat top copy machine. With the top open, put your hand at the left (if it scans from that side). After it passes your hand, put it on the right side. It'll see your hand again.
When I was in middle school, we took at trip to Washington DC. They did a panoramic picture of the class. The photographer had the girl on the left side of the picture move, as soon as she was out of the shot, and run around to the right side. She showed up twice, like twins. It was easier than editing her in later, or at least then it was. Now, it's a piece of cake in Photoshop.
Serious? Seriousness is well above my pay grade.
"Now, it's a piece of cake in Photoshop."
So you used Photoshop to replace the second instance of the girl with a piece of cake. But that wouldn't look like there were twins.
it is only after a long journey that you know the strength of the horse.
I think I can see the Virgin Mary in that blury photo. The scientologists are right, it really is true that we came from another planet!
Ok so the explanation is pretty clear to most everyone... if you believe that propaganda!!!
Clearly the larger so-called "satellite" is a Romulan Bird of Brey that has come to hunt down the Odyssey satellite before it either A) discovers the Romulans cloaked mission control base for Earth domination (by crashing into it) or B) becomes sentient like "V---ger" did.
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!!
...when NASA employees with a warped sense of humour get their hands on a copy of Photoshop
"Who says nothing is impossible? Some people do it every day!" - Alfred E. Neuman
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.
If you do the math its because for certain values of the exact geometry there are multiple solutions in the range [0,pi] for t in the equation k.t+phi = tan(v.t) (where k is the rotational rate of the camera, v is the velocity of the flyby probe, phi is the angle of the camera to the probe at time t=0).
Obviously there are other solutions as the camera rotates round again, and I've assumed the camera is static and the probe is in a constant speed linear path.
The above maths is pretty simple, every graduate should be capable of computing it. Its hardly rocket science. Oh hang on, maybe it is!
It is a simple question of dispersion in the atmosphere. Take telescopes for instance ...Ground-based telescopes can seldom provide resolution better than 1.0 arc-seconds while the Hubble's resolution is about 10 times better, or 0.1 arc-seconds. Not just because its a good camera but because it is up where it doesnt have to deal with the atmosphere.
And the cameras on the MGS do not rely on a good lens as much as they do rely on the electronics. It uses a linear array CCD which will scan the night sky one line at a time (much like a CRT actually). And it is not limited to the visible region of the spectrum. UV and near infrared have way too much information to give than just an optical picture.
Most the pics released finally are almost always digitally enhanced and represented in the visible region of the spectrum. The kids these days will not be fired up about astronomy if all they see is an output of wavelets in an array.
Except of course its not like TV at all which scans in horizontal lines.
The picture was scanned from the right hand side in vertical strips. As the picture is being scanned, the viewed Mars Odyssey is moving from right to left. The camera is also rotating from right to left.
Picture a car on the opposite side of the road moving in opposite direction flying by the side window of your car as you look out (90km) and then the camera rotating and "catching up" as it scans, with the same car out the back window (135km).
If you RTFA, you will see it mentioned that this picture and one other picture taken by the Mars Global Surveyor were the first, not that this particular photo was the first. The European Space Agency's Mars Express was the first extraterrestrial satellite imaged in this method. The Mars Express was imaged April 20, 2005, and it seems Mars Odyssey was imaged this month (can't see a date, I've looked several places).
My other sig is just as lame
The picture they posted here_ fig1.jpg
http://photojournal.jpl.nasa.gov/figures/PIA07941
does help a bit- the camera is rotating and because it builds up the image over time it sees (the relatively near by) object twice.
I guess when imaging the surface they have to rotate the orbiter/camera to account fo the fact the orbiter is moving relative to the planet surface faster than they can take the picture.
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...
Hang on... the Martians are intelligent, and yet they're watching our TV?
Real Daleks don't climb stairs - they level the building.
But hey.. What do I know..?
Remember, there are no stupid questions. But there are a lot of inquisitive idiots.
Ah, I see what you're saying. But it can't be so, because that would cause both images to be total blurs. Each image of the Odyssey must be within a single scanline of the camera. Actually, come to think of it, the camera probably takes an instant shot of a vertical strip, waits until the craft has rotated and then takes another strip. It doesn't scan like a scanner at all, it just wouldn't work, methinks.
Money for nothing, pix for free
Why didn't they just take the pictures before they sent them? That way they could get much closer than 90km.
"I've got more toys than Teruhisa Kitahara."
Obviously Mars Odyssey was using the Picard maneuver.
One line blog. I hear that they're called Twitters now.
Later that day, Mars Odyssey filed a restraining order against Mars Global Surveyor with claims of stalking.
One line blog. I hear that they're called Twitters now.
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.
~ 135 km range: *-x
~ 90 km range: o--X
:-D
Amazing...we send probes all the way to Mars to they can photograph...each other.
Kinda like when Americans visit other countries...all they want to do is talk to other/i> Americans.
____
~ |rip/\/\aster /\/\onkey
That's a couple of the vipers launched from Battlestar Galactica. They think they've finally found Earth, and are quite confused as to why they've renamed it Barsoom. The damn cleric in the Tombs of Kobol was a bit drunk when he made the map to Earth.
I mean, we really are in stone age. That could be anything. That could be a blob, it could be a light bulb exploding in a dark room. I need concrete evidence that that was what NASA claims it was.
e vastator2.jpg
If I saw something like this
http://wso.williams.edu/~rfoxwell/starwars/pics/D
there would be no doubts in my mind.
But NASA? Pffffft.
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.
Seriously, what is it with Slashdot and this common grammatical error? It seems as if the majority of people on this site use the wrong form of verbs when referring to a company or organization.
My take on it is that they're trying to sound proper, but they aren't really that familiar with the proper rules of grammar.
When referring to the company or organization as an entity, it is a singular noun. Rarely will it be a plural noun. I see this incorrect usage in nearly every thread. Simply looking at the company's webpage and seeing how they refer to themself would give you a pretty good idea of the proper usage.
In NASA's case:
http://www.nasa.gov/about/highlights/index.html
NASA is, NASA has, etc. Singular.
Its the same frame exposed twice.
Score:5, Informative?? Score:-1, Factually Incorrect.
It is a single exposure, but the frame is sweep-scanned. The closest analogy I can think of is the way a fax machine sweepscans a page one line at a time. It's like scanning a fax and half way through you reverse direction of the rollers pulling in the paper. It would sweep-scan the same half of the page on the way out. The printed fax would be a single exposure, but the two halves would have the same thing twice.
A simpler (but really rotten) analogy would be a photo with a mirror across half a room. It's a single exposure, but everything appears twice.
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