How vulnerable is GPS technology?

[zombie]

That is dangerous what if we launch a nuclear weapon against India and missile land in Iran..This is dangerous stuff.

lol..If it can US will make sure it hits Ahmedinejad. That should get the Iranians either mad or happy at Pakistan.

 

[gambit]

The current version of the BrahMos missile uses a hybrid GPS-GLONASS navigation. The GPS is the primary navigational aid, but in case the GPS fails, malfunction or is intentionally switched off, the missile can switch over to the GLONASS. Affects the accuracy, but ensures that the missile is not going east when it is meant to go west!

One important note people seems to have missed -- neither GPS nor GLONASS belongs to those who uses them, except for their creators. So if you want to use either or both systems, do not pick a fight with either US or Russia. Or both of us. But if you want to fight each other, then by all means use either GPS or GLONASS or both, we will sit back and collect data on battlefield efficacy of satellite assisted navigation.

 

[applesauce]

One important note people seems to have missed -- neither GPS nor GLONASS belongs to those who uses them, except for their creators. So if you want to use either or both systems, do not pick a fight with either US or Russia. Or both of us. But if you want to fight each other, then by all means use either GPS or GLONASS or both, we will sit back and collect data on battlefield efficacy of satellite assisted navigation.

lol very true,

anyways blocking gps signals simply presents a radar jamming like scenario, it will have to be local, to overcome it just send some strike fighters

 

[Developereo]

The current version of the BrahMos missile uses a hybrid GPS-GLONASS navigation. The GPS is the primary navigational aid, but in case the GPS fails, malfunction or is intentionally switched off, the missile can switch over to the GLONASS. Affects the accuracy, but ensures that the missile is not going east when it is meant to go west!

So GLONASS is only consulted if GPS fails? How would the missile know when it is getting false, albeit consistent, readings from GPS -- sending it east when, in fact, it truly believes it is going west?

 

[gambit]

So GLONASS is only consulted if GPS fails? How would the missile know when it is getting false, albeit consistent, readings from GPS -- sending it east when, in fact, it truly believes it is going west?

Inertial Navigation. The INS is essentially a closed and self contained dead reckoning navigator. But any INS is prone to drift due to many reasons, from the gyros' mechanical tolerances to temperature gradients inside the system. Because of drift an INS is often correlated against an external source of navigational indicator, like the FB-111's astro tracking system...

FB-111A.net

Part of the sensor suite were the Singer-Kearfott AN/APN-185 Doppler radar and the Litton AN/ASQ-119 Astrotracker.

What the Astrotracker does is to track the positions of the stars, even in daylight, and verify them against what the INS says. The GPS or GLONASS is no different in principle when used with an INS. The INS is the navigation equipment of final resort when all else failed.

 

[Screaming Skull]

So GLONASS is only consulted if GPS fails? How would the missile know when it is getting false, albeit consistent, readings from GPS -- sending it east when, in fact, it truly believes it is going west?

The BrahMos missile control system is based on Inertial navigation with terminal homing. The GPS/GLONASS data is required only at the terminal stages by which time the missile would have already reached close to the target via INS. It is a high precision missile, meant to take out very small targets selectively from a group of potential targets. For this the exact coordinates are required not only to locate the target precisely but also to activate the warhead for optimal destruction of the target. The software used is such that it does comparative iterations between the GPS and GLONASS data and calculates the coordinates exactly using the onboard computers. Hence, the missile can be misled only if both GPS and GLONASS feed it with incorrect data.

 

[Screaming Skull]

One important note people seems to have missed -- neither GPS nor GLONASS belongs to those who uses them, except for their creators. So if you want to use either or both systems, do not pick a fight with either US or Russia. Or both of us. But if you want to fight each other, then by all means use either GPS or GLONASS or both, we will sit back and collect data on battlefield efficacy of satellite assisted navigation.

That s true. That s why we are working on our own GPS!

Indian Regional Navigational Satellite System - Wikipedia, the free encyclopedia

Description

The proposed system would consist of a constellation of seven satellites and a support ground segment. Three of the satellites in the constellation will be placed in geostationary orbit. These GEOs will be located at 34 East 83 East and 132 East longitude. The GSOs will be in orbits with a 24,000 km apogee and 250 km perigee inclined at 29 degrees. Two of the GSOs will cross the equator at 55 East and two at 111 East. Such an arrangement would mean all seven satellites would have continuous radio visibility with Indian control stations. The satellite payloads would consist of atomic clocks and electronic equipment to generate the navigation signals.

According to a presentation by A Bhaskaranarayana to a meeting of COSPAR in Montreal on 15 July 2008, IRNSS signals will consist of a Special Positioning Service and a Precision Service. both will be carried on L5 (1176.45 MHz) and S band (2492.08 MHz) The SPS signal will be modulated by a 1MHz BPSK signal. The Precision Service will use BOC(5,2).

The navigation signals themselves would be transmitted in the S-band frequency (2–4 GHz) and broadcast through a phased array antenna to maintain required coverage and signal strength. The satellites would weigh approximately 1,330 kg and their solar panels generate 1,400 watts.

The System is intended to provide an absolute position accuracy of better than 20 meters throughout India and within a region extending approximately 2,000 km around it.

The ground segment of IRNSS constellation would consist of a Master Control Center (MCC), ground stations to track and estimate the satellites' orbits and ensure the integrity of the network (IRIM), and additional ground stations to monitor the health of the satellites with the capability of issuing radio commands to the satellites (TT&C stations). The MCC would estimate and predict the position of all IRNSS satellites, calculate integrity, makes necessary ionospheric and clock corrections and run the navigation software. In pursuit of a highly independent system, an Indian standard time infrastructure would also be established.

Well the description says that it will provide coverage of about 2000 km around India. But learned space scientists will know that 7 sats with 3 in GSO can provide much greater coverage. At least in India's context, enough to cover whole of China if need be.

 

[gambit]

The BrahMos missile control system is based on Inertial navigation with terminal homing. The GPS/GLONASS data is required only at the terminal stages by which time the missile would have already reached close to the target via INS.

So what the Brahmos does is to fly in a dead reckoning course to the general vicinity of the target, of course the longer this distance the greater the drift induced error, then upon reaching the guesstimated target area, the Brahless would acquire any satellite navigation signals, perform a quick correlation, perform any course corrections, then descend on the target. At this point, any terrain information from radar would be helpful. Keep in mind that since the Brahfull is a cruise missile, hence familiar with terrain, the more maneuvers the missile perform in order to keep perspective with terrain, the greater the uncorrected drift induced error will be at the final target area, therefore it would be wise to perform minor course corrections along the flight in order to minimize or even zero out any navigational error at the end.

 

[Screaming Skull]

So what the Brahmos does is to fly in a dead reckoning course to the general vicinity of the target, of course the longer this distance the greater the drift induced error, then upon reaching the guesstimated target area, the Brahless would acquire any satellite navigation signals, perform a quick correlation, perform any course corrections, then descend on the target.

That is precisely what I meant.

At this point, any terrain information from radar would be helpful. Keep in mind that since the Brahfull is a cruise missile, hence familiar with terrain, the more maneuvers the missile perform in order to keep perspective with terrain, the greater the uncorrected drift induced error will be at the final target area, therefore it would be wise to perform minor course corrections along the flight in order to minimize or even zero out any navigational error at the end.

Course correction along the flight is performed via onboard sensors and gyros and not through GPS or GLONASS aid. The INS used in the BrahMos is a modified version of the one used in the Indian Prithvi Ballistic missiles, which don’t use GPS at all and yet have a very low CEP. As I said before the GPS/GLONASS aid is only required for pin point accuracy and target recognition. In fact the GPS/GLONASS aid is used only in the land attack variant of the missile as it is meant to take out targets, which are insignificant in terms of size, in a cluster of large buildings. The ship based missiles don’t use any GPS/GLONASS aid as the targets are significantly larger.

Here watch this test launch video of the BrahMos and you will know what I mean. Watch from 56s onwards.

 

[Thomas]

I doubt Russia would take out the U.S. GPS satellites since the U.S. then would take theirs out. Neither side is interested in a tit for tat satellite shooting war.

 

[gambit]

Course correction along the flight is performed via onboard sensors and gyros and not through GPS or GLONASS aid.

This tells me that you have a flawed understanding of navigation and guidance.

If you know where you are going, from your home to the office for example, then the method to get there is 'navigation'.

AIRCRAFT NAVIGATION SYSTEM WITH VERTICAL GUIDANCE - Patent 3705306

In an aircraft navigation system of the type including a computer with a memory for storing ground coordinates of a start point and a destination point,...

If you do not know where you are going but are determined to travel anyway, then the method of getting 'there', wherever 'there' might be, is called 'guidance'. Say you are on your very familiar way to the office and a ball bounces across the road in front of you...

Halt...

At this point, you are no longer under 'navigation' because of an expected event and this event presented itself as an obstacle that you must avoid. To avoid the bouncing ball, you steer your car around it but you cannot steer the car unless you have knowledge and capability to 'guide' the car. Steering is strictly mechanical. Guidance imply foreknowledge, no matter how little. With your intelligence, you know how to guide your car to avoid hitting the ball and you perform the action with just enough steerage so that you do not undershoot or overshoot.

Once you avoided the obstacle, you will be in a 'course correction' mode but you cannot do so unless there are EXTERNAL cues to tell you that you are off or on course. Those external cues are other cars, the curb, the next city block, pedestrians, a few stores alongside the street and the list goes on. You take in all these external cues, compared them against your stored coordinates of where you came from (home) and where you want to be (office) and you mentally said to yourself 'Oy vey...I had better induce steerage X degree to port and X degree to starboard.' Then you will be back to 'navigation' as if nothing had happened.

Navigation, guidance and steerage are distinct entities. The differences are subtle but they are crucial in programming a navigation computer.

If a cruise missile is programmed in a flight path that include ALL known features loosely called 'obstacles', the missile has 'navigation' and 'steerage'. No 'guidance'. The missile would be flying blind. It would know that after its air data computer took in accelerometers inputs, after X km traveled it is supposed to induce X degree of steerage to port for X amount of time, then steerage to starboard for X amount of time, then have blind faith that there is nothing in front of its path. There are no course corrections there.

The Brahmos is not launched from an underground silo, a fixed known location. This missile is supposed to be mobile, therefore its launch locations are unknown. It may know its target but because it is occasionally moved, it will never know its launch location. Do not take that literally. What I mean is that in programming the navigation computer, launch coordinates are omitted, allowing the operator to input them as situations demand. The missile may on Monday know it is at so-and-so coordinates but on Tuesday it is suddenly aware of another set of coordinates. Target coordinates can be treated the same way -- unknown. It may contain a set of launch and target coordinates but those can be changed as well.

So if the Brahmos is supposed to fly from undetermined launch locations to undetermined targets, that mean the missile cannot be programmed with flight paths that would include ALL known features, aka obstacles. That is equivalent to the differences between home and office versus restaurant to office versus office to bar versus bar to home. Every time you take one of those paths, there will be different external cues for you to process and different unexpected obstacles for you to guide yourself around. To have effective guidance, the missile require some external cues to tell it: 'Whoa...There is a land rise above X height ahead'. The missile then would query its directives to see if it is allowed to overfly this height or guide itself around this land rise. Is the Brahmos this sophisticated? If the Brahmos is programmed to fly no below 10,000 ft then there is no need to make it 'smart' as there would be very little land rise above that altitude. Then all you need is navigation and steerage. Could radar be the supplier of those external cues? Yes. Radar are used in navigation all the time. Radars are eyes.

Most Internet blurbs about these things do not bother to make fine technical distinctions. From my experience, I dare say to support the Brahmos's claim of accuracy, radar and satellite navigation guidance are employed at least in the periodic, if not constant, mode of operation. The lower the standard flight altitude, the more likely it will require active guidance from external sources.

Here is one source that make those technical distintions...

LM News Reference: Guidance, Navigation and Control

For purposes of the following discussion, a distinction is made between guidance (orbital alteration or redirection of the LM) and navigation (accumulation and processing of data to define the proper guidance to be accomplished).

You can look at the distinction this way: Navigation is beyond line-of-sight (LoS) while guidance is within LoS, hence the phrase 'terminal guidance'. What is meant by 'terminal'? That you are at the end of your destination -- office. Are you semi-important enough at work to have an assigned parking space? No? That mean everyday, you must use external cues to find a parking slot for your car and very likely that space will be different from day to day. That is 'terminal guidance'. Same for any missile that has the 'terminal guidance' feature. The missile MUST use external cues via active radar to identify its target or use satellite assistance, a different type of external cues, to properly orient itself to a ground point. When it comes to satellite assistance, do not confuse 'target' with the ground point. Your target may be a building concrete set into the earth, but if the missile is given a ground point coordinate 100 meters to the north, its satellite assisted terminal guidance will direct the missile to THAT ground point. To YOU, the building is the 'target' and the mission was a failure but to the missile, the ground point coordinates is 'target' and the mission was a success.

Another way to look at these distinctions...

A 'navigator' will present a course to the pilot to the general area, but once the B-17 arrive at that area, the pilot will guide the aircraft into what he deems the best position for his bomb run. The bomber may arrive from the south, but based upon factors like local weather or damages already done by previous bombers, the pilot may decide to make his run from the southeast direction and would made adjustments. The 'navigator' has no inputs at this point. That is the difference between navigation and guidance.

The INS used in the BrahMos is a modified version of the one used in the Indian Prithvi Ballistic missiles, which don’t use GPS at all and yet have a very low CEP.

Ballistic missiles do not maneuver very much and their warheads, while on the descent, is even more aerodynamically restricted from maneuvers.

Read this about the MX's inertial navigation...

Advanced Inertial Reference Sphere

Very little of the precision of this guidance system is even exploited during a ballistic missile flight, it is mostly used simply to maintain guidance system alignment on the ground during missile alert without needing an external reference through precision gyrocompassing. Most ICBMs require an external alignment system to keep the INS in synch with the outside world prior to launch. The AIRS is probably as good as any INS for ICBM guidance needs to get.

Note the highlighted, it is not 'the ballistic missile', which would imply specifically the MX. Whereas the operative 'a ballistic missile' imply ballistic missiles in general. The more accurate the missile knows its launch location relative to its target, the lower its warhead's CEP. The mechanics of a ballistic trajectory make the INS is more important at launch than in flight.

The adaptation of the Prithvi's INS into a cruise missile has more to do with economics than anything else. Make sense. Why bother to develop a cruise missile type INS when there is a current system that will work just fine and you would be able to exploit all the features of that system as the ballistic missile had no use for those features?

As I said before the GPS/GLONASS aid is only required for pin point accuracy and target recognition.

Satellite assisted navigation does not give target recognition, only location.

In fact the GPS/GLONASS aid is used only in the land attack variant of the missile as it is meant to take out targets, which are insignificant in terms of size, in a cluster of large buildings. The ship based missiles don’t use any GPS/GLONASS aid as the targets are significantly larger.

Target size imposes no restrictions on launch method. If the Brahmos is able to hit a very specific target, like a small power shack adjacent to a large lab, then...

1- The missile is given ground point coordinates to that power shack. This imply satellite assistance.

2- The missile is equipped with some abilities to visually acquire unique features of that power shack. This imply radar, IR and/or EO methods.

3- Both of the above, which would be best.

If what you say is true -- that ship based Brahmos is NOT equipped with satellite assisted navigation -- then I say it is either very shortsighted planning or that there is something else hinting at a technical constraint.

Here watch this test launch video of the BrahMos and you will know what I mean. Watch from 56s onwards.

2HDVhX7PZHg[/media] - Indian Army Launches World's Fastest Cruise Missile -BraHmos (Sustained Mach-3 Speed)

That is a propaganda video. It may mean something to some people, but nothing technically valuable to me.

 

[pakdefender]

GPS receivers used for Sat Navs , Trecking etc ( non-differential basically ) can be jammed using sufficiently powered noise modulated signals in the GPS freq band.

You baiscally need a signal genrator and a power amplifier , for military use the problem will this will be that a HARM will find it with not problem.

Phrak Magazine had published a complete circuit for doing this , it still avaibale there

 

[applesauce]

you can buy civilian gps jammers today for a fairly cheap price

 

[Engr786]

Replacement of GPS is there as with the help of space wave propagation we can track & even disguise any system even AH-64D's guidanace.

 

[adegogo]

GPS JAMMER is illegal in some areas as I know, but it is legal here in my country, so I just bought one for myself the other day from jammerall.com/categories/GPS-Jammers/ ,it is working great and helps me much.