As an astronomer, I've always been pretty impressed with these military/commercial imaging satellites because they basically use the technology we use to look up at the skies, but instead to look down at the earth.
Here's a quick intro to the technology for those who aren't familiar.
Basically, these companies (or the air force) send a 1-ton spacecraft up on a large rocket (made by Lockheed Martin generally) and put in in geosynchronous orbit around the earth. These orbits are something like 500 miles above the earth, which means that they orbit the earth once every 1.5 hours or so. (you can try the math if you like, F=ma, a=v^2/r, a=GM/r^2)
They specifically put it into what's called a "sun-synchronous" orbit -- which means that its orbit takes it alternately over the light and dark side of the earth each half of the trip. And wherever the satellite passes over the earth (on the light side), it will be approximately 10:30 am. (if you have trouble visualizing this, draw a line in your mind from sun to earth, then align the plane created by the satellite's orbit vertically with this line.)
So every orbit, the satellite traces out a wide swath of territory it can take pictures of (like peeling strips off a potato). These swaths are perhaps 10km wide, and can extend for 100s or 1000s of kilometers in length. Note that it can take pictures straight down if it wants, or it can aim to the side slightly. This is why satellite pictures may not look like they were taken from directly above, but rather from the side a little bit. Black and white images are standard, color will take longer of course.
So it turns out that with these satellites, every place on the earth will eventually pass beneath the path during daylight, and will be able to be imaged. They will give you statistics such as "Revisit frequency is 50% of the earth within 24 hours, or 100% within 3 days, more if you don't require the satellite to be directly overhead". (This is used to plan observations, or to tell imaging clients how soon a target can be seen, which might be important for the military, for example).
Pricing of the images is of course based on recovering the development and launch costs, so individual images will be pretty expensive. Custom tasks are even more expensive. But remember, the satellite is continuously taking images (it's not waiting for clients), and they store the data for future use.
So far, the only kids of satellite imagery have been still-images, but many speculate that live video has been possible for several years now (like in "enemy of the state"). I'm quite sure the us military has this capability, but I myself have never heard a definitive response on this question...
Hope you find this useful!
what if people don't have good imaginations?
on
This is IT?
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· Score: 1
1. Ok, I'm visualizing moving forward on my new scooter.
2. Hey, look at that -- this is pretty neat!
3. Ok, now I'm visualizing turning the corner...
4. Wow, it knows what I want!
5. Ok, let's go a little faster.
6. Cool.
7. Umm. That tree is coming towards us awful fast, visualizing not hitting it.
8. Hello, anyone there?
9. AAARRARAGGGHGHHHHHH!
10. Ok, visualizing getting out of the hospital bed...
As a professional astronomer, I never cease to be amazed at how freely people will donate their time and resources to a project, that for the immediate future has absolutely no tangible benefits or results. It really demonstrates how science can motivate.
Well, that and the competition aspect of it too...
But anyway, it was probably the best practical idea astronomers have had in a while -- if you can't afford a supercomputer, get everyone else to create your supercomputer for you! As we all know, people hesitate to spend money on hardware -- who among us would have even donated $5 to the SETI project? But when you pass that cost along as the associated cost of running the computer you've already bought, people readily shell out the "bucks" or cpu time. I wonder how much "money" has been "donated" to the SETI project in this way?
it's really about being more efficient
on
Virtual Astronomy
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· Score: 2, Informative
I have the feeling that some may be confused about what virtual astronomy is. So perhaps I can try to clear up a little bit.
Much of astronomy now is done by individual astronomers going to telescopes and pointing to interesting objects in the sky. Each researcher has lists of several objects they'd like to observe, and on their night at the telescope, they skip from object to object. This is good for the individual astronomer, but unfortunately, wastes a lot of time, because a lot of the time must be spent on finding the object, moving the telescope, etc. Because observing time is so precious, a new way has been discovered to make it more efficient -- virtual observing.
Virtual observing mas made possible by the great advances in database technology and hardware storage technology. It works by having a telescope (which used to be used by astronomers for individual objects, for example) survey broad areas of sky, subsequently storing that data on disk. Efficiency is increased, because you essentially put the telescope in one position and let the sky move over it, instead of having to point from object to object. Also, setting the telescope up for one survey run is much better than setting it up for the 2 or 3 observers each night, who may have different requirements.
Then, when an "observer" wants to look at an object, instead of asking the telescope to point there specially for him/her, now he/she just goes to the database and retrieves the image. It's better for the astronomer too -- quicker, no need to wait for a clear night, or your time to observer, and no need to fly out to the observatory. There are also lots of gains to be had in the science, too, because some experiments require large swaths of continuous sky to analyze, instead of just individual objects. Much of the work demonstrating the expansion of the universe relies on having such data, and it's only been possible recently with the first virtual observing projects.
The challenges are, as stated in previous posts, compiling all the data so that it can be accessible in an easy way by observers around the world, storage, and data processing. It's going to be an exciting time for astronomy, and I think that our knowledge is going to increase rapidly!
phillipe and sofar are correct -- the Chixulub crater impact has been known about for several years ago as the "cause" or associated event with the K-T boundary. If you want to read more about it, I suggest an entertaining scientific chronicle of the discovery called "T. rex and the Crater of Doom", a book by one of the famous father-son teams in paleogeology -- Walter and Luis Alvarez.
An interesting thing to note is how they actually discovered the crater site -- it was by working with scientists from oil companies! Turns out that oil companies have significant geologic mapping efforts (in order to discover more oil of course) all over the world, and in this case, they (eventually) decided to help these geologists by sharing some of their information.
I find the topic of asteroid/near-Earth object *discovery* to be even more interesting. This is going to take a very intensive effort which combines observations (telescopes) and computing, because if you want to discover these things, you've got to work with automated systems that can log astronomical object movement in an automated fashion.
I'm an American, and you know, I never fail to be fascinated/frustrated at how vigorously other Americans attack China. Who said that our system is the best? And who are you to criticize another country for providing for its people in the best way they deem possible? It's not like the leaders are in it for the fun of it -- good god, they have to serve 1.2 billion people! Let me see you manage a country that large, by giving people all the same freedoms we enjoy here. We have enough trouble already, with only 1/5 the population...
If you think about it, it's like people here have been programmed to hate China just because it's one of the few remaining "Communist" countries around. Do we really need another enemy? Why create one when China doesn't want to be an enemy?
Never mind that their increasingly capitalist structure has given far more people over there opportunities than can be said about some of our population here. When you criticize China, are you doing so because you've really thought about the issues, or because that's all the media has told you to do here? Sometimes the freedom of thought is more quashed here than in less-priviliged, knowledge-embracing countries...
There are actually two peaks in the meteors this year, one of them before dawn on the east coast here, and another one about 6-8 hours later which is supposed to be even bigger.
People in the US will miss the second peak shower, but that means that if you're in Asia, you're in the prime viewing zone.
Also, it's new moon, so there's no other light in the sky to diminish the view! Unless you live in a bright city, and then, oh well... (try to get out into the country if possible)
Slashdot Mirror
As an astronomer, I've always been pretty impressed with these military/commercial imaging satellites because they basically use the technology we use to look up at the skies, but instead to look down at the earth.
Here's a quick intro to the technology for those who aren't familiar.
Basically, these companies (or the air force) send a 1-ton spacecraft up on a large rocket (made by Lockheed Martin generally) and put in in geosynchronous orbit around the earth. These orbits are something like 500 miles above the earth, which means that they orbit the earth once every 1.5 hours or so. (you can try the math if you like, F=ma, a=v^2/r, a=GM/r^2)
They specifically put it into what's called a "sun-synchronous" orbit -- which means that its orbit takes it alternately over the light and dark side of the earth each half of the trip. And wherever the satellite passes over the earth (on the light side), it will be approximately 10:30 am. (if you have trouble visualizing this, draw a line in your mind from sun to earth, then align the plane created by the satellite's orbit vertically with this line.)
So every orbit, the satellite traces out a wide swath of territory it can take pictures of (like peeling strips off a potato). These swaths are perhaps 10km wide, and can extend for 100s or 1000s of kilometers in length. Note that it can take pictures straight down if it wants, or it can aim to the side slightly. This is why satellite pictures may not look like they were taken from directly above, but rather from the side a little bit. Black and white images are standard, color will take longer of course.
So it turns out that with these satellites, every place on the earth will eventually pass beneath the path during daylight, and will be able to be imaged. They will give you statistics such as "Revisit frequency is 50% of the earth within 24 hours, or 100% within 3 days, more if you don't require the satellite to be directly overhead". (This is used to plan observations, or to tell imaging clients how soon a target can be seen, which might be important for the military, for example).
Pricing of the images is of course based on recovering the development and launch costs, so individual images will be pretty expensive. Custom tasks are even more expensive. But remember, the satellite is continuously taking images (it's not waiting for clients), and they store the data for future use.
So far, the only kids of satellite imagery have been still-images, but many speculate that live video has been possible for several years now (like in "enemy of the state"). I'm quite sure the us military has this capability, but I myself have never heard a definitive response on this question... Hope you find this useful!
1. Ok, I'm visualizing moving forward on my new scooter.
2. Hey, look at that -- this is pretty neat!
3. Ok, now I'm visualizing turning the corner...
4. Wow, it knows what I want!
5. Ok, let's go a little faster.
6. Cool.
7. Umm. That tree is coming towards us awful fast, visualizing not hitting it.
8. Hello, anyone there?
9. AAARRARAGGGHGHHHHHH!
10. Ok, visualizing getting out of the hospital bed...
As a professional astronomer, I never cease to be amazed at how freely people will donate their time and resources to a project, that for the immediate future has absolutely no tangible benefits or results. It really demonstrates how science can motivate.
Well, that and the competition aspect of it too...
But anyway, it was probably the best practical idea astronomers have had in a while -- if you can't afford a supercomputer, get everyone else to create your supercomputer for you! As we all know, people hesitate to spend money on hardware -- who among us would have even donated $5 to the SETI project? But when you pass that cost along as the associated cost of running the computer you've already bought, people readily shell out the "bucks" or cpu time. I wonder how much "money" has been "donated" to the SETI project in this way?
I have the feeling that some may be confused about what virtual astronomy is. So perhaps I can try to clear up a little bit.
Much of astronomy now is done by individual astronomers going to telescopes and pointing to interesting objects in the sky. Each researcher has lists of several objects they'd like to observe, and on their night at the telescope, they skip from object to object. This is good for the individual astronomer, but unfortunately, wastes a lot of time, because a lot of the time must be spent on finding the object, moving the telescope, etc. Because observing time is so precious, a new way has been discovered to make it more efficient -- virtual observing.
Virtual observing mas made possible by the great advances in database technology and hardware storage technology. It works by having a telescope (which used to be used by astronomers for individual objects, for example) survey broad areas of sky, subsequently storing that data on disk. Efficiency is increased, because you essentially put the telescope in one position and let the sky move over it, instead of having to point from object to object. Also, setting the telescope up for one survey run is much better than setting it up for the 2 or 3 observers each night, who may have different requirements.
Then, when an "observer" wants to look at an object, instead of asking the telescope to point there specially for him/her, now he/she just goes to the database and retrieves the image. It's better for the astronomer too -- quicker, no need to wait for a clear night, or your time to observer, and no need to fly out to the observatory. There are also lots of gains to be had in the science, too, because some experiments require large swaths of continuous sky to analyze, instead of just individual objects. Much of the work demonstrating the expansion of the universe relies on having such data, and it's only been possible recently with the first virtual observing projects.
The challenges are, as stated in previous posts, compiling all the data so that it can be accessible in an easy way by observers around the world, storage, and data processing. It's going to be an exciting time for astronomy, and I think that our knowledge is going to increase rapidly!
"And we have seen and do testify that the Father sent the Son to be the Savior of the World" -- I suppose this refers to George W.? :)
phillipe and sofar are correct -- the Chixulub crater impact has been known about for several years ago as the "cause" or associated event with the K-T boundary. If you want to read more about it, I suggest an entertaining scientific chronicle of the discovery called "T. rex and the Crater of Doom", a book by one of the famous father-son teams in paleogeology -- Walter and Luis Alvarez. An interesting thing to note is how they actually discovered the crater site -- it was by working with scientists from oil companies! Turns out that oil companies have significant geologic mapping efforts (in order to discover more oil of course) all over the world, and in this case, they (eventually) decided to help these geologists by sharing some of their information. I find the topic of asteroid/near-Earth object *discovery* to be even more interesting. This is going to take a very intensive effort which combines observations (telescopes) and computing, because if you want to discover these things, you've got to work with automated systems that can log astronomical object movement in an automated fashion.
I'm an American, and you know, I never fail to be fascinated/frustrated at how vigorously other Americans attack China. Who said that our system is the best? And who are you to criticize another country for providing for its people in the best way they deem possible? It's not like the leaders are in it for the fun of it -- good god, they have to serve 1.2 billion people! Let me see you manage a country that large, by giving people all the same freedoms we enjoy here. We have enough trouble already, with only 1/5 the population... If you think about it, it's like people here have been programmed to hate China just because it's one of the few remaining "Communist" countries around. Do we really need another enemy? Why create one when China doesn't want to be an enemy? Never mind that their increasingly capitalist structure has given far more people over there opportunities than can be said about some of our population here. When you criticize China, are you doing so because you've really thought about the issues, or because that's all the media has told you to do here? Sometimes the freedom of thought is more quashed here than in less-priviliged, knowledge-embracing countries...
There are actually two peaks in the meteors this year, one of them before dawn on the east coast here, and another one about 6-8 hours later which is supposed to be even bigger. People in the US will miss the second peak shower, but that means that if you're in Asia, you're in the prime viewing zone. Also, it's new moon, so there's no other light in the sky to diminish the view! Unless you live in a bright city, and then, oh well... (try to get out into the country if possible)