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View Full Version : OT - any ideas why the US military shut down access to the meteor satellites?



andy_b
06-14-2009, 12:38 AM
the space debris info seems harmless enough.

http://news.yahoo.com/s/space/20090611/sc_space/militaryhushupincomingspacerocksnowclassified;_ylt =Al5mPEYJWBf5OeUpHw2O8yX737YB;_ylu=X3oDMTE1NmxmYzA zBHBvcwMzBHNlYwN5bi1jaGFubmVsBHNsawNtaWxpdGFyeWh1c 2g-

so it leaves me wondering, has the military put some debris up there that it doesn't want anyone knowing about? are they ABOUT to put some debris up there they don't want anyone knowing about? or are some space rocks heading our way that are about to make the dinosaur extinction look like a fire cracker?

andy b.

Evan
06-14-2009, 01:10 AM
Those satellites are for spotting rocks and stuff that has already hit us as well as nuclear tests in the atmosphere. With North Korea and Iran coming close to being able to make a real nuclear weapon the are probably concerned about giving out information that would allow calibration of the detection thresholds of the sensors.

Detecting incoming threats such as asteroids before they hit is the job of the Lincoln Near-Earth Asteroid Research (LINEAR) Program. These are adaptive optics telescopes that are good enough to easily spot missing tiles and insulation on the shuttle in orbit.

dp
06-14-2009, 01:10 AM
More likely just another Obama administration budget cut.

mayfieldtm
06-14-2009, 01:11 AM
Probably... they don't want people to know the full capabilities of their satellites.

Tom M.

Jim Shaper
06-14-2009, 01:16 AM
If you think it's something funky, keep an eye on the induced error they can encode into the GPS signals to return. I'd guess that's next on the domestic pre-war situation checklist.

Evan
06-14-2009, 01:34 AM
That is called "Selective Availability" and I have a feeling they are already turning it back on. I went to town a couple of weeks back and wore my Garmin wrist GPS. When I got home I hooked it to the 'puter and forgot about it for a week while it just keep recording it's location. This is what it recorded and the errors are much larger than usual. It was sitting in my living room next to the main window where it has a good look at the sky. The error looks to be on average 100 to 200 feet which is typical of what to expect when selective availability is turned on. The use of Selective Availability is strictly up to the president and all it takes to turn it on or off is his orders.

http://ixian.ca/pics6/gps1.gif

Evan
06-14-2009, 01:41 AM
This is the same thing but recorded one year ago. I didn't leave it on very long but the scatter is typical of full accuracy with Selective Availability turned off.

http://ixian.ca/pics6/gps2.gif

Jim Shaper
06-14-2009, 01:41 AM
So you're saying you don't live on an active fault line? :D

Doesn't surprise me at all that it's back on. I was more surprised they turned it off considering it would be relatively low level skill (for an electronics guy) to adapt a gps to a radio controlled aircraft and all of a sudden you have a drone with autopilot for a few hundred bucks.

gnm109
06-14-2009, 04:37 AM
More likely just another Obama administration budget cut.


If Obama cut a budget, that's big news,

Your Old Dog
06-14-2009, 06:57 AM
Evan, your printout may have looked much better had you left the watch under a clear sky instead of near a window. You know, I'm sure, that the gps works better with more spread on the birds, that's why most if not all gps units show you a menu of where all the birds are on the horizon.

Neat printout at anyrate. Looks like the one I got from my gps while at anchor on a 50 foot rope in a small lake. That one was due to wind and currents and not satelite availability.

Evan
06-14-2009, 10:38 AM
The Garmin Forerunner 205 is supposed to work inside as well as out. Sitting by the window it has a view of about half the sky so I wouldn't expect that spread, especially since a year ago it never looked like that.

Selective Availability can be turned on and off like a light switch and the amount of error on the civilian channels can be set to whatever they want. It is completely flexible and they can tune it for time of day to suit when the satellites pass over different parts of the planet as well as the type of error that is introduced. Errors can be random or they can be a Drunkard's Walk error which won't screw up survey instruments that take a long term set of readings and average it.

Paul Alciatore
06-14-2009, 12:03 PM
Well, lets see:

Satellite detects N bomb tests.

Obama is making nice to Iran. It's called trust our enemies until they stab us in the back.

Obama probably wants to make nice to North Korea also. Why should they not be given an equal opportunity for back stabbing?

If satellite detects North Korean test and public gets data from it,

Obama can not deny that North Korea made the test.

Or Obama can not put out false information about the test if word gets out anyway (other resources or even North Korea announcement).

So Obama can not make nice with them in spite of the test.

So, Obama orders satellite data restricted.

Why should he allow facts to stand in the way of diplomatic stupidity?

Makes perfect sense.

Optics Curmudgeon
06-14-2009, 04:10 PM
Of course it makes sense, you want desperately for it to. Then again, if (insert name of currently hated administration / party here) was to have opened whatever resource to public use the response would be "look what they're giving away! We're doomed now!". The satellites in question detect atmospheric tests, they don't tell you diddly about underground tests, and the whacko in NK knows that. On the other hand, you can get info about missile launches from them, and the extent of that capability is something that you (they) may want to keep close. As for selective availability, it was shut off years ago, and the new block of satellites going into service don't even include the capability. It was found to be more trouble than it was worth, and with the FAA including GPS as an element of the new navigation package the chance of it returning is slim to none.

Joe

Evan
06-14-2009, 06:26 PM
The FAA navigation system includes and requires ground based GPS transmitters to achieve the necessary accuracy for zero-zero landings. A GPS transmitter doesn't have to be on a satellite, it can be anywhere you like and putting it on the ground makes it much more accurate since it isn't subject to all the errors of movement the space based clocks are subject to. That is called "Differential GPS" and the US is covered with DGPS transmitters. If SA is turned on and you are in the US you probably won't see a difference. Selective availability has no affect on the ground stations and so can still be implemented as required. If you really think it isn't in the new satellites then the question I have for you is "Why not?" It costs exactly nothing to implement, it's all in software. The software is not only all they need but it can be updated any time they wish.

Selective availability was first shut off during Desert Storm because the military didn't have enough mil spec GPS units to equip all troops that needed them. They quickly solved that problem by cleaning out Radio Shack and turning off SA. Carter later decided to keep it turned off because the benefits were obvious for commercial users. The other reason for turning it off was a simple matter of national pride. The Russian Glonass system is just as good and also reaches to medium orbit. The Eu Galileo system is also available and the Chinese are putting up their own system. None of the systems are compatible so the US system has the most hardware available.

philbur
06-14-2009, 06:53 PM
Desert Storm followed by Carter. Is my recollection of history that far out of whack???:)

Phil

[QUOTE=Evan]
Selective availability was first shut off during Desert Storm because the military didn't have enough mil spec GPS units to equip all troops that needed them. They quickly solved that problem by cleaning out Radio Shack and turning off SA. Carter later decided to keep it turned off because the benefits were obvious for commercial users. QUOTE]

Evan
06-14-2009, 06:59 PM
Ooops. I meant Clinton.

lazlo
06-14-2009, 07:38 PM
That is called "Differential GPS" and the US is covered with DGPS transmitters. If SA is turned on and you are in the US you probably won't see a difference.

Agreed, although many consumer GPS units out there don't have WAAS receivers. I think most modern GPS units, including most (all?) of the Garmin wrist units do...

This is from the PNT.gov web page. "PNT" is Positioning, Navigation, and Timing -- "the National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT) established by Presidential directive to advise and coordinate federal departments and agencies on matters concerning the Global Positioning System (GPS) and related systems".

http://pnt.gov/public/sa/faq.shtml

At what time was SA turned off?

Selective Availability ended a few minutes past midnight EDT after the end of May 1, 2000. The change occurred simultaneously across the entire satellite constellation.

Will SA ever be turned back on?

The United States has no intent to ever use SA again. To ensure that potential adversaries do not use GPS, the military is dedicated to the development and deployment of regional denial capabilities in lieu of global degradation.

I heard that SA will be left on in certain parts of the world. Is it still on in my country?

No. You have been misinformed. Selective Availability was a global degradation of the GPS service. It could not be applied on a regional basis. By turning it off, the President immediately improved GPS accuracy for the entire world. The United States has no intention of reactivating SA ever again.

Users in the U.S. and the rest of the world should now be experiencing the same basic GPS accuracy of 10-20 meters or better.

dp
06-14-2009, 08:53 PM
Users in the U.S. and the rest of the world should now be experiencing the same basic GPS accuracy of 10-20 meters or better.

That's about what I get on my Blackberry phone. It cross-checks well with my Garmin. The underlying maps used by Verizon are not so accurate. It claims I'm sitting in my neighbor's house :)

Evan
06-14-2009, 09:02 PM
No. You have been misinformed. Selective Availability was a global degradation of the GPS service. It could not be applied on a regional basis. By turning it off, the President immediately improved GPS accuracy for the entire world. The United States has no intention of reactivating SA ever again.



Sure. Let's see, we have a satellite that knows where it is to within 20 nanoseconds. SA requires putting random bit values in the least significant 8 bits of data transmitted once every million nanoseconds.

Nah, there is no way, too complicated. And of course, a different president would never issue an executive order that reversed one by a previous president. It just isn't done. :rolleyes:

dp
06-14-2009, 09:47 PM
Nah, there is no way, too complicated. And of course, a different president would never issue an executive order that reversed one by a previous president. It just isn't done. :rolleyes:

It may be contractually binding to keep things as accurate as possible. And you know BO would never go back on a contract. :confused:

Evan
06-14-2009, 10:29 PM
What really gets me fuming is when I hear bald faced lies like "It could not be applied on a regional basis. . Not only can it be done it can be turned on and off like turn signals and all the satellites can be coordinated so that the moment a specific target is in range a completely bogus signal can be delivered. I know this only because it is so trivial to do. The military would never pass up such capability, especially since it can be installed at any time after launch.

tony ennis
06-14-2009, 11:21 PM
I recall some time ago, civilians could have access to satellite data from a satellite that could detect subtle changes in ocean level. Suddenly, the US government turned off civvy access, no explanation given. My conjecture was that the satellite could pick up the wake/disturbance of submerged submarines.

andy_b
06-15-2009, 12:37 AM
Desert Storm followed by Carter. Is my recollection of history that far out of whack???:)

Phil


that was just wishful thinking on Evan's part. :)

JUST KIDDING

andy b.

andy_b
06-15-2009, 12:41 AM
I recall some time ago, civilians could have access to satellite data from a satellite that could detect subtle changes in ocean level. Suddenly, the US government turned off civvy access, no explanation given. My conjecture was that the satellite could pick up the wake/disturbance of submerged submarines.

from reading i have done that is EXACTLY how they track the submarines. in fact, isn't there an operational "caterpillar drive" like in Red October? submarines are cool. i bet there is as much technological development in them as military aircraft.

andy b.

Teenage_Machinist
06-15-2009, 01:29 AM
I think Obama is honorable enough not to be screwing with nuclear tests- barely.

But still, these things can vary. It likely is for a totally insignificant reason.

Evan
06-15-2009, 04:47 AM
Time for my favorite Ronald Reagan quote:

Politics is supposed to be the second oldest profession. I have come to realize that it bears a very close resemblance to the first.

Evan
06-15-2009, 04:50 AM
The Russians have had the Caterpillar Drive for many years. It's a well known principle that takes advantage of the fact that sea water is a pretty good conductor. By running a current through the water you can make it move with a magnetic field. The field of study is called magnetohydrodynamics and I recall seeing a science fair project on the exact principle when I was entered in the same State science fair in 1966.

The system take a lot of power and produces very low thrust. It also produces chlorine gas due to electrolysis that can be detected at the surface.

The Satellite in question used laser range finding to determine ocean levels to within a few centimetres. It had completed the full set of low resolution passes when it mysteriously "failed" completely. There is no doubt that the wake of a moving submarine could be detected on the surface. A large submarine displace a LOT of water as it moves.

Strange, I already posted this reply quite some time ago and it vanished. Fortunately I kept a copy.

dp
06-15-2009, 11:03 AM
There have been several attempts to develop a commercial drive using this principle but they're not efficient in terms of consumed energy and don't solve any problems. The electrical/magnetic signature make them useless in subs, and they are not silent as they generate a lot of gas bubbles. I suspect too that any living thing that is sucked into the engine comes out dead on the other end. If so they leave a trail of dead things behind as a tell-tale.

dp
06-15-2009, 11:08 AM
The Satellite in question used laser range finding to determine ocean levels to within a few centimetres. It had completed the full set of low resolution passes when it mysteriously "failed" completely. There is no doubt that the wake of a moving submarine could be detected on the surface. A large submarine displace a LOT of water as it moves.

It would also reveal the depth (from the size of the disturbance), speed, and direction of the sub. Tactical nukes don't need much more to get the job done. So if all this is true then subs are pretty much short duty cycle platforms in a super powers war.

Evan
06-15-2009, 11:30 AM
The solution to detection is to sit still for periods of time. Or, to move very slowly at great depth. Both options are exercised by the subs on both sides so detection is not a given. I suspect other techniques may also be used such as changing course while gently gliding deeper on the glide planes.