do modern aircraft, including military, require the use of GPS? If GPS fails, what happens? What prompted the question was a news story that Russia is preparing a bomb of some sort that would wipe out all GPS satellites. Believe it was a BBC story. Story implied, but did not say so directly, that one bomb would do it. Nor did it give any details about how it would work or how many civilian or military aircraft it would affect. does the AWACs system depend on GPS?
I sincerely doubt that story is true.
Many aircraft rely on GPS systems to determine their location. They also have other systems that can be used to determine where they are. With enough reference points, a quality GPS system can determine its location to within a few feet. Radar is one of the backup systems for aircraft, but it is not as accurate as GPS.
From the little I know, the only type of bomb that could take out a GPS satellite would be one that produces an EMP pulse. The inverse square law indicates that the bomb would have to be relatively close to affect the satellite. Since GPS satellites are distributed in orbit around the world, I sincerely doubt that one bomb would take out all satellites. Don't forget about ground-based GPS systems.
Does the AWACs system depend on GPS? - No.
Many planes use navigation systems to determine their location. Those systems use GPS to update their computed location. If they lose GPS, they use their heading and computed ground speed to compute their location. Over time, the navigation system drifts from the aircraft's actual location due to minor errors in heading and actual ground speed.
AWACs reports the location of an intruder using its location data and the intruder's distance and heading from the AWAC's location. The reported position of the intruder is accurate enough for an intercept.
Navigation systems, including GPS are separate from the flight controls.
As long as the flight control systems are working and the pilot can see the ground, even the most advanced aircraft can still be navigated using a Mk I Eyeball.
There are several different ways to navigate besides following roads. (IFR does not really mean "I follow roads")
NDB - non-directional beacons. These are ground-based transmitters. Regular radio stations can be used as well. Arrow on the ADF points toward the tuned station.
VOR - also called omni - a VOR sends out a signal that indicates where, in a 360 degree circle around the transmitter, the plane is located. Two or 3 can be used to triangulate your location on a map.
VOR/DME - as above, but also indicates the distance direct to the VOR.
There is also "dead reckoning" using compass, aircraft speed, and wind speed/direction.
The folks who fly the big planes over the ocean can afford INS - inertial navigation systems which only need to know where they started from to compute where they are now. And celestial navigation like sailors did for centuries can still work.
None of these need GPS.
There have been reports that countries (including Russia) have "spoofed" GPS to make it show incorrect location data, affecting ships and aircraft. This would strengthen the need to have alternative non- GPS navigation options.
Remember also that the Russians have a DIFFERENT system called GLONASS. Because of the specific deployment that their satellites use, it gives better coverage near the poles. IF they could spoof the GPS system, which reportedly they can, they would still have their own system.
do modern aircraft, including military, require the use of GPS? If GPS fails, what happens? What prompted the question was a news story that Russia is preparing a bomb of some sort that would wipe out all GPS satellites. Believe it was a BBC story. Story implied, but did not say so directly, that one bomb would do it. Nor did it give any details about how it would work or how many civilian or military aircraft it would affect. does the AWACs system depend on GPS?
This is complete nonsense.
First of all, GPS is a constellation of satellites, not just one. You would have to take out at least a half dozen to impact more than just a small area.
And not even military equipment relies on GPS. The military is still very much a "belt and suspenders" type of organization. Most navigation by ships, aircraft and even a lot of land vehicles is still by "inertial navigation". In other words, they have a computer that tracks where it is based on how fast it is traveling in what direction. That technology has actually been around since WWII, and only relies on leaving from a fixed location to know exactly what you are. And that is still the primary navigation system for US missiles like the Tomahawk.
Because GPS relies upon external sources and can be disabled or interfered with, that is only used as a verification system. But if the GPS and Inertial do not agree, the GPS readings are actually discarded and the inertial location is used.
There is also radio navigation, where fixed locations (for aircraft normally airports) send out steady signals, and with two or more the pilot and computer can plot their location through triangulation amazingly effectively.
I would say that in order, the navigation systems for aircraft (military, commercial and private) are the following.
1. Inertial
2. Radio Navigation
3. Eyeball and visual tracking of a map
4. Simply knowing heading and speed
5. GPS
Even the Tomahawk Missile works in that way to this day. Inertial is the primary navigation, secondary is a computer that verifies location with a camera based on known visual landmarks (roads, buildings, bridges, dams, etc). That is why so often they are seen over roads and cities. They are literally following the road with their inertial and visual systems. GPS is the final fallback, in the event of say heavy cloud cover so visual does not work and the inertial goes offline.
I spent a great many years in the military, and as advanced as a lot of our equipment was, a hell of a lot of it was ancient. Primarily because it just worked and was reliable.
Every one of our PATRIOT launchers has computers and GPS, but we actually place them and plot their locations with a sextant from the 1940s and box from the 1970s that mounts to a HMMWV that uses inertial navigation to show where you are at. We place them visually, with an honest to god Sextant (M2 Aiming Circle), GPS, and through that inertial navigation box. And the GPS is the one discarded if they do not agree.
And we still input fixed things into the RADAR like buildings and mountains with sextant readings. Once again, GPS is only a check but we never rely upon it.
only relies on leaving from a fixed location to know exactly what you are.
That is not exactly true.
Inertial navigation systems also require that the vessel's heading be known. Ocean currents affect the vessel's speed, faster or slower, and cause the vessel to drift to left or right. If the vessel's actual location is not determined and the inertial navigation's location updated, a large location error can occur.
I worked on a R&D program and the aircraft's location data had a significant error location when it landed.
Inertial navigation systems also require that the vessel's heading be known.
Hence, needing to know the course and speed you have taken since leaving the fixed location. Which is what I said.
In other words, they have a computer that tracks where it is based on how fast it is traveling in what direction.
And yes, things like wind and currents can affect that (as can changes in altitude on ground travel}. But that is generally fractional when it comes to travel and is why that is not the only system used.
M2 Aiming Circle
After I was wounded, I was "voluntold to reclassify from 11B Infantry to 11C "Mortar-Man" aka "Indirect Fire Infantry" and had to be taught a variety of things, including how to use an M2 Aiming Circle. Our primary system for Plotting Targets was the then (2007/8) MIFS (Mortar Indirect Fire System) based of what the Artillery had been using for years (a bastard form of Windows 95!). {That is another story.} Our back-up system was Not any of the previous (electronic) computers, but the Good Ole M2 Aiming Circle.
It is mounted on a wooden tripod (to minimize metal that might effect the compas). Pardon me, I have forgotten the nomenclature of the sight/compass, that is used along with the M2 Aiming Circle. It is nearly 0500, and I don't have my reference materials handy.
My point is that if a US Army Artillery officer from c.1861 (the beginning of the US Civil War) or even c.1831 and the establishment of the USMA at West Point would be able to Plot a Fire Mission for modern mortars or artillery if advised about the ranges based upon (how many) propellent charges are to be used. It is just Math!
Our back-up system was Not any of the previous (electronic) computers, but the Good Ole M2 Aiming Circle.
PATRIOT is a tad different, as we are aiming up, not out and down. But we use the M2 to make sure the launchers are far enough apart, and aimed in the correct direction. And for the RADAR we use it to input obstructions in the distance that will be tagged in the computer as fixed hard points and ignored (so they do not see the mountain or building or whatever on the RADAR image itself). As well as the angle of the horizon in the distance (flat, up-slope or down-slope).
And that is important, as we might see a mountain in the distance. But with that information we well the RADAR to ignore the mountain, and it will notify us and we can target an aircraft flying between us and the mountain.
And we might have to "eliminate" other things on the screen. I remember one operator not doing it properly, and we had a freeway at the edge of RADAR range. Where it kept reporting low flying helicopters until the Lieutenant realized what was wrong and blocked it off. The semi trucks on the freeway were being interpreted by the computer as helicopters. *laugh*
Granted it's not the same thing, but when GPS became a thing in ambulances, I'd turn off the screen when a newer partner wanted to see where we were responding to with the GPS. Then I'd hand them a map book and a street guide.
The GPS was too close-up, in my opinion, back then...
As already mentioned, GPS isn't always reliable, especially around warzones or objects of interest concerning Russia or Israel. This is done by radio interference, either simply suppressing GPS signals by stronger broadcast in same frequency or by spoofing, where signals imitating the legitimate are introduced, or both.
Read, for example, on the East Baltic GPS anomaly. It's a partially "natural" phenomenon as GPS constellation does have particularly poor coverage in the area, but it's irregular nature had also been tied to certain Russian warships based in Kaliningrad. Either way, quite often many planes in the area report GPS readings error large enough for the data to be discarded automatically.
As for the alleged Russian anti-satellite weapon, the rumor has it they fly at least one nuke in orbit currently, and may potentially launch more. That orbital nuke then would be detonated into the orbit of the target satellite polluting it with debris even if not affecting directly, and may theoretically take out entire shells of satellites sharing an orbital. Such action doesn't actually require a nuke, a conventional shrapnel round would or could be as effective or better. Depending on the height of the orbit, such attack would render the target orbit unusable from years (leo) to decades (sso) to "forever" (geostationary), significantly endangering everything else.
As already mentioned, GPS isn't always reliable, especially around warzones or objects of interest concerning Russia or Israel. This is done by radio interference, either simply suppressing GPS signals by stronger broadcast in same frequency or by spoofing, where signals imitating the legitimate are introduced, or both.
Back in 1993, we had the Yinhe Incident.
Where a Chinese ship suspected of carrying chemical weapons for Iran was in the Indian Ocean. The US got multiple nations to deny it docking rights, and started to spoof their GPS causing it to go around in circles and being unable to navigate reliably.
They kept that up for 24 days until they finally agreed to allow the ship to be inspected.
If GPS fails, what happens?
See "Flight Management Computer (FMC) "Fail Down" sensor logic" from James Albright for the hierarchy of data sources. For more about GPS in general, Global Navigation Satellite System (GNSS)
Global Positioning Satellite (GPS) System.
An article related to this topic: Commercial pilots rattled by surge of GPS spoofing attacks sending them bogus signals
Aviation officials and regulators have said that spoofed Global Positioning System signals are spreading beyond active conflict zones, and have seen a recent surge – resulting in more than 1,000 flights being affected every day in August.
The article also says:
The airlines say their pilots are equipped with several ways to navigate precisely should they be confronted with GPS interference.
So, first, it's fairly common, and second, it won't result in chaos or crashes.
GPS spoofing or jamming tends to be effective against certain classes of inexpensive precison-guided weapons which use GPS rather than (far more expensive) inertial navigation or other systems. On the other hand, blowing up the GPS jammer has become a common countermeasure.
As others have said, it would require a number of weapons to attack the GPS network. GPS satellites are in MEO (medium Earth orbit), an altitude of approximately 20,200 km (12,550 miles). While Russia does have launch vehicles capable of reaching MEO (obviously, since its own GLONASS navigation system is also at MEO), they aren't cheap or easily mass-produced, and you're not just trying to reach MEO, you're trying to rendezvous with a small, fast-moving target. Doable, but not easy.
Mostly, attacking GPS looks to be low payoff, high cost.
There is also a political risk: GPS satellites also contain nuclear weapons detection capabilities. An attack on them might easily be considered an attack on our early warning capability and thus an act of war. Add to that it will require a number of simultaneous heavy-lift launches, some of which will necessarily initially track towards the US and Europe, and this isn't a likely scenario.
The distance between GPS satellites likely precludes any single-launch scenario where the launch vehicle then deploys a number of interceptors. Unless you can position your interceptor with such precision that the GPS satellite will inevitably hit it while orbiting, it's a waste, and GPS satellites have maneuvering capabilities. As soon as there's a launch and the first satellite is hit, the others will likely shift orbits, making for an incredibly difficult interception scenario.
Excellent summation, using open sources. I concur!
Using open sources, I will dissent, a bit, about capabilities for degrading or disabling GPS, GLONASS, or other satellite networks. The USA, and possibly other powers (Israel in particular), probably have the capability(ies) to neutralize GPS and similar systems.
Consider their open source doctrines and demonstrated capabilities, as well as articles in Proceedings (of the Naval Institute) and other similar professional journals. The US armed forces (and other entities) have demonstrated concern that "someone" could disable the GPS network and other satellite systems. Military and naval forces tend to "mirror" their potential threats; in other words, presume their opponents have similar (or greater) capabilities than themselves. Of course, too often a nation/force has underestimated their foe(s). But that history is at a minimum paid lip service too; even if not "spoken" about.
Math, and many of the STEM fields are something that both Russia and China have proven to be extremely capable in. However, for at least a hundred years both have proven to have significant problems with Quality Control in manufacturing even the most vital items. Both Russia and China have doctrines that embrace massive overkill. Partly this has to do with Communist Doctrine decreeing that it is Military Science not Military Art as is practiced by Western nations.
The USA (and probably several other entities) could use one (or more) launch vehicle to deploy multiple ASAT Hunter/Killer systems. It would take time to maneuver each ASAT to intercept their intended targets (even if having ranged attack capabilities). Multiple nations continuously monitor everything in orbit, in particular recent launches. The USA, Russia, the PRC, France, India, Israel, Japan, the UK, just to name the most prominent. So it would be complicated, if not highly improbable, to stage ASAT capability without being detected.
The nations mentioned above carefully study other nations orbital platforms to determine their capabilities. Such as fuel capacity/maneuver time, platform endurance, and numerous other factors. So, "hiding" an ASAT or several in a routine communications, reconnaissance, or GPS platform, would be problematic. Not to mention the difficulties of Op-Sec.
Grey Wolf is very much correct about the "political" dangers of such an attack. Actually, a surprise neutralization of the GPS, GLOSNASS, etc. might well trigger a panicked over reaction.
I really should look this up before posting this: "There has never been an attack by one nation (or other entity) upon another nation's orbital assets." Going by open source information. Tom Clancy and other techno thrillers have described the probable use of such devices. Not just ASATs using "Kinetic Kill" aka a projectile(s) or fragments, but also airborne lasers, and other DEW (Directed Energy Weapons). There have been some discussions of possible "degrading" of orbital systems, but nothing has been definitively stated in an open source.
Using open sources, I will dissent, a bit, about capabilities for degrading or disabling GPS, GLONASS, or other satellite networks. The USA, and possibly other powers (Israel in particular), probably have the capability(ies) to neutralize GPS and similar systems.
Until 1998, GPS was not very accurate at all on purpose. Built into the US system was a random number that would throw off the results by I want to say up to 100 meters in a random direction. But by that time we had more satellites and constellations and the computers were able to use even more birds to pinpoint even that purposeful deflection so they stopped doing it.
But the capability is still there. So the 10-15 feet of inaccuracy that is in the system now in time of war could with a few commands go right back to that degree of randomness. Which would be much more impactful on say Chinese armaments, which rely much more on GPS for guidance than similar US armaments.
They are only able to get their CEP (Circular Error Probable - think accuracy for ballistic weapons) through GPS, while the US had been getting incredibly accurate CEP through inertial navigation for decades.
We were getting a CEP of 25 meters on ICBMs in the 1980s long before GPS. But China could only get a CEP that low in recent decades because of GPS. Throw that random number back in, and their ballistic weapons would go right back to having an accuracy measured in hundreds of meters instead of the two dozen meters or so they have now.
"There has never been an attack by one nation (or other entity) upon another nation's orbital assets." Going by open source information. Tom Clancy and other techno thrillers have described the probable use of such devices.
And that is an entirely accurate statement. The US has destroyed two satellites with ASAT weapons that I know of, but both of the satellites were owned by the US. The first in 1985, the second in 2008. Russia has done it once in 2021 and destroyed one of their satellites. And China did it in 2007, once again by knocking out one of their own satellites.
The weapon that Clancy described in "Red Storm Rising" was the one the US used in 1985. A modified AGM-69 SRAM launched from an F-15 the year before the book was published.