Iran shoots down US drone

[Ryan Thunder]

Have you read the original farsi? Could it be that they did not want to disclose their methods? They did not want to admit that they have a mostly intact drone untill they had it hidden in a school gym. Remarkable that that's a difficult idea to accept for its simplicity.

I find it kind of amusing that you think that the simplest answer is that they hacked it and landed it intact when one of the alternatives is that they blew it into itty bitty little pieces with one of those shiny SAMs they bought from the Russians and they're lying about it.

[Sea Skimmer]

Its not unlikely that the wings of RQ-170 are designed to come off in the first place, so it can be air transported protected inside a box to areas of operations, it sure doesn't look like its would have enough range to self deploy besides the fact that it was being hidden somehow for some time. This is true of RQ-1 and RQ-9 Predator/Reaper drones.

I find it kind of amusing that you think its simpler that they hacked it and landed it intact rather than that they blew it into itty bitty little pieces with one of those shiny SAMs they bought from the Russians.

Russia embargoed the sale of S-300 if that's what you mean. They do have some other systems but none of them are very good, nor at all numerous. Iran also doesn't have much in the way of an air defense system in the first place. If they shot it down a fighter intercept would be more likely then a SAM launch. Even a stealthy drone at night (not sure if this was night or day loss) can still be seen by a pilot with NVGs.

[Ryan Thunder]

Russia embargoed the sale of S-300 if that's what you mean.

Oh. My bad. When did that happen?

They do have some other systems but none of them are very good, nor at all numerous. Iran also doesn't have much in the way of an air defense system in the first place. If they shot it down a fighter intercept would be more likely then a SAM launch. Even a stealthy drone at night (not sure if this was night or day loss) can still be seen by a pilot with NVGs.

Well, that, then.

[Kanastrous]

It's not the idea that the wings might detach that I find odd, it's the possibility that the seam would appear to be so large and pronounced. From the usual layman's reading on stealthy aircraft, that seems like an undesirable feature.

[UnderAGreySky]

I *still* think the simplest answer is a crash. They've been operating in hot and sandy places for heavens sake - it's not inconceivable! Everything else could just be parlour tricks.

Point taken on the GPS power levels, Sea Skimmer, but I still find it hard to believe it was spoofed. And I don't think the Chinese or Russians will share such high tech stuff with them, it would mean the Americans get to know about it faster.

I've also heard - WARNING: UNSUBSTANTIATED RUMOUR AHEAD - that this was not the only UAV in the air at the same time, but one of three. When the ill-fated one lost contact, the other two were diverted to watch over it. GPS or other hacking has been dismissed by the US because the other two aircraft showed no signs of disturbance. /END UNSUBSTANTIATED RUMOUR

[Sea Skimmer]

Oh. My bad. When did that happen?

Last year when the UN hit Iran with a heavy weapons embargo, Iran is now amusingly suing Russia for breach of contract.

Now, Iran may have gotten one or two S-300 firing units from Belarus much earlier around 2001, but they've never been seen. Belarus has been accused of selling advanced air defense gear to a couple nations, like Iraq, that never got verified so that that claim for what its worth. Iran did parade what they claimed was a copy of S-300 a few times, but it looks pretty damn fake and they've never showed it firing or even deploying the radar. One likely theory is they are really trying to copy stuff they got from Belarus but simply can't make it work yet, which would be incredibly unsurprising, and so are just parading mockups for the moment. One can of course laugh at Iranian claims that the Iranian clone is far superior to the Russian system.

It's not the idea that the wings might detach that I find odd, it's the possibility that the seam would appear to be so large and pronounced. From the usual layman's reading on stealthy aircraft, that seems like an undesirable feature.

I dunno, one speculation related answer could be, maybe it gets filled in service with stealth putty or other gap filler like they use on the B-2? Seems unlikely, but possible like every other answer...

[Sea Skimmer]

I *still* think the simplest answer is a crash. They've been operating in hot and sandy places for heavens sake - it's not inconceivable! Everything else could just be parlour tricks.

Point taken on the GPS power levels, Sea Skimmer, but I still find it hard to believe it was spoofed. And I don't think the Chinese or Russians will share such high tech stuff with them, it would mean the Americans get to know about it faster.

I agree in large part; but I'd also point out that the US has just begun orbiting a improved generation of GPS satellites, and soon will start launching even further improvd ones, so its also possible that the trickery will soon no longer work. Aside from any possible harder to crack signal advantages, the new satellites are also just going to have higher power transmitters, and the ability to further increase power over spot areas with some kind of steered antenna. Among other features they are to have is supposed to be much longer encryption sequences as part of an entirely new signal. Take that for what you want... just future proofing or resolving known risks issues? No guess on my part.

I've also heard - WARNING: UNSUBSTANTIATED RUMOUR AHEAD - that this was not the only UAV in the air at the same time, but one of three. When the ill-fated one lost contact, the other two were diverted to watch over it. GPS or other hacking has been dismissed by the US because the other two aircraft showed no signs of disturbance. /END UNSUBSTANTIATED RUMOUR

That would be a good answer. One would also imagine that if it was jammed in any way US ELINT satellites couldn't help but pick that up, L band goes into space as easily as it comes back down. But such rumors are also rather unlikely to ever be confirmed or denied. I suspect though that this screw-up, whatever its cause, will be high profile enough that more information WILL leak out, but it could be months or even a couple years.

[Sarevok]

Did some searching on GPS spoofing. Apparently the knowledge to spoof at least civilian GPS openly existed for nearly a decade. The US Department of Transportation even issued advisories warning that civilian GPS is not secure anymore.

In one test researchers stole a cargo truck by spoofing GPS, just like how the Iranians are claiming they stole the drone.

[Sea Skimmer]

Civilian GPS is a much different story between the simple code used; and the fact that many civilian GPS devices are cheap and only listen to one or two satellites at a time.

[Sarevok]

Slight correction there Great Leader !

Four satelites are needed to get a GPS fix. Why ?

In the previous example, you saw that it took only 3 measurements to "triangulate" a 3D position. However, GPS needs a 4th satellite to provide a 3D position. Why??

Three measurements can be used to locate a point, assuming the GPS receiver and satellite clocks are precisely and continually synchronized, thereby allowing the distance calculations to be accurately determined. Unfortunately, it is impossible to synchronize these two clocks, since the clocks in GPS receivers are not as accurate as the very precise and expensive atomic clocks in the satellites. The GPS signals travel from the satellite to the receiver very fast, so if the two clocks are off by only a small fraction, the determined position data may be considerably distorted.

The atomic clocks aboard the satellites maintain their time to a very high degree of accuracy. However, there will always be a slight variation in clock rates from satellite to satellite. Close monitoring of the clock of each satellite from the ground permits the control station to insert a message in the signal of each satellite which precisely describes the drift rate of that satellite's clock. The insertion of the drift rate effectively synchronizes all of the GPS satellite clocks.

The same procedure cannot be applied to the clock in a GPS receiver. Therefore, a fourth variable (in addition to x, y and z), time, must be determined in order to calculate a precise location. Mathematically, to solve for four unknowns (x,y,z, and t), there must be four equations. In determining GPS positions, the four equations are represented by signals from four different satellites.

[Sea Skimmer]

No you do not understand what I mean. It does not matter if you need three satellites or nine. The issue is that the antenna and receiver/decoder hardware in many GPS devices only listens to one or two of those satellites signals at any given instant. GPS codes come in pulses, the receiver shifts which signal it listens in on and decodes from pulse to pulse, and generates a location based on a history of pulses stored in memory. For stationary or slow moving applications this works okay, but it’s a little less accurate and has a significantly reduced update rate. A good receiver meanwhile can simultaneously listen to every satellite it can acquire, and differential GPS ground stations where available. As a result it effectively calculates position on a continuous basis using potentially a dozen or more sources.

[Sarevok]

Ah I see.

By the way is there truth to claim commercial GPS chips you can buy can not operate at speeds above 500 miles/hour or 60000 feet as dictated by US government ? So that chips intended for consumer applications or hobbyists tinkering with rc planes dont't end up in weapons apparently.

[UnderAGreySky]

Sea Skimmer: Most of today commercial GPS receivers can do 12 satellites at a time. I've worked with REALLY cheap ones, and they were all 12-channel.

Sarevok: They're handicapped by what rate they can process stuff. Most commercial GPS receivers run at 1 Hz, meaning at 500 miles an hour you could be hundred of yards off course (220m) or change your heading significantly This means your course-corrections are of more serious magnitude and they affect your performance. 4/5 Hz ones are expensive and take a bit more power. I don't think they are limited by design, IMO it's the money that is a factor. I stand to be corrected though.