(Continued from previous post)
I would strongly suggest reading https://en.wikipedia.org/wiki/AGM-88_HARM, at least the Ukraine section. It describes how Ukraine should be hunting SAM site with HARMs. Random targets of opportunity that NATO sigint doesn't know about exist, but are rare. A fighter would have to "stumble across" them.
The idea of "just adding another ESM receiver" to a Russian fighter and using it to geolocate Radars using triangulation is basically a total fantasy. The reasons why are many. Very few fighter aircraft carry "ESM grade" receiving systems at all, and certainly not "ESM grade" DF systems. Their RWRs bearing accuracy is approximate at best. Much money spent optimizing the antenna placement and calibration of these RWRs. Lots of time is spent in anechoic chambers doing this. The idea that you can easily add another antenna and receiver somewhere on the aircraft and get good results is so improbable as to frankly be laughable.
In order to generate an "ESM grade" line of bearing that use useful in triangulating anything at many km range, that line of bearing (LOB) has to be quite accurate. You also may need a way to compensate for "cone error" due to the fact you are in the air at altitude and the radar is on the ground. The further away you are, the more accurate your "LOB" needs to be. In addition you need a "cross bearing" for even a simple triangulated solution. Where do you get the "second" bearing? Well, you can just fly for a while and get another measurement. How far do you have to fly? Well, that depends. If you are a long way from the radar, you have to fly a long way. You also have to fly "in the right direction", which you don't know. There is a thing called Geographic Distortion of Position (GDOP) If you take two bearing measurements from positions that are "close" together, you get two lines of bearing that intersect each other at a very acute angle. The Circular Error Probability (CEP) ellipse has a very, very long major axis. You have nothing approaching a firing solution. OK, fly for "a few" minutes. Make another measurement. However, since the problem we are trying to solve is locating an emitter that shuts down quickly, it will probably be gone before you fly far enough to beat the GDOP. It also may well be that the "best" direction to fly takes you into locations that are distinctly "unsafe" for your aircraft.
When one adds in the fact this notional target is a "radar target of opportunity", choosing to prosecute it with a JDAM means you aren't doing your "original" mission. If you are "hunting" radars, you are going to need to fly to where you can see the radar. The JDAM range of 45 km from altitude is well within the range of S-X00 missile systems. You probably cannot survive flying around for minutes trying to get a geolocated solution to program into your "ipad", even if you had a DF system that could do that and software to help you. If you have a HARM, launch it and get out of Dodge or get low enough you can't "see" the radar on your RWR any more.
There are sigint aircraft that do have "precision" DF systems that can geolocate radars. These aircraft fly in areas where they are "safe" from threats (they hope), so they can stay there for a long time. Radars can shut down and come back on later. These aircraft have software that processes the many thousands of LOBs collected and "makes sense" of a lot of them, yielding good targeting solutions. These solutions are available (at least to US consumers) in time frames from hours to a day or so, depending.This is very "old" technology, but it works. The US also has high-flying elint drones that can do precision DF measurements. These drones use antenna technologies that have been perfected for this task. The data is uplinked and can be used to geolocate "pop up" targets relatively quickly. The drone may take a while to fly far enough to beat the GDOP, but generally it isn't going to get shot down, we hope. It also can fly over hostile territory more easily. If it gets targeted, it is much less of a loss than an RC-135. The P-8 also contains systems that can do a similar task. Presumably Ukraine has access to much of this capability.
It should be noted that the best way to geolocate emitting targets in today's world is almost always NOT "triangulation". There are other methods, including some "old" ones (TDOA) that work well and don't require LOBs. Nearly all these methods involve flying some distance in order to generate a good "solution" and they work better if the aircraft maneuvers while doing so. These approaches mostly don't require a LOB measurement as such. This turns out to be a big advantage as it removes lots of physical limitations on the antennas. An example can be found here, but it is one of many. https://apps.dtic.mil/sti/tr/pdf/ADA452783.pdf In so far as I know, this particular research never led to a deployed system, but other similar ones have.
It also should be noted that if several sensors make simultaneous measurements of the same emitter at different geographic locations very accurate emitter location is possible. It can be done "after the fact" by post-mission processing of data collected from different platforms. It can also be done in "real time" by consumers who receive all the data via a satellite link or other means. This includes the various "sensors" themselves. It also should be noted that the F-35 has the capability to do this sort of thing, both as a sensor and as a consumer. It also has the ability to persist in a high threat airspace much longer that any SU-24 can. All that money did indeed buy us something :-).
Obviously, Ukraine has no F-35s, but there is no reason they can't have sigint aircraft of their own if they need them and it is a high enough priority. The equipment required to do it is mostly available COTS and that which isn't is easily within Ukraine's ability to procure from defense contractors. This makes much more sense and bang for the buck than trying to hang an ESM system on a MIG.
I would strongly suggest reading https://en.wikipedia.org/wiki/AGM-88_HARM, at least the Ukraine section. It describes how Ukraine should be hunting SAM site with HARMs. Random targets of opportunity that NATO sigint doesn't know about exist, but are rare. A fighter would have to "stumble across" them.
The idea of "just adding another ESM receiver" to a Russian fighter and using it to geolocate Radars using triangulation is basically a total fantasy. The reasons why are many. Very few fighter aircraft carry "ESM grade" receiving systems at all, and certainly not "ESM grade" DF systems. Their RWRs bearing accuracy is approximate at best. Much money spent optimizing the antenna placement and calibration of these RWRs. Lots of time is spent in anechoic chambers doing this. The idea that you can easily add another antenna and receiver somewhere on the aircraft and get good results is so improbable as to frankly be laughable.
In order to generate an "ESM grade" line of bearing that use useful in triangulating anything at many km range, that line of bearing (LOB) has to be quite accurate. You also may need a way to compensate for "cone error" due to the fact you are in the air at altitude and the radar is on the ground. The further away you are, the more accurate your "LOB" needs to be. In addition you need a "cross bearing" for even a simple triangulated solution. Where do you get the "second" bearing? Well, you can just fly for a while and get another measurement. How far do you have to fly? Well, that depends. If you are a long way from the radar, you have to fly a long way. You also have to fly "in the right direction", which you don't know. There is a thing called Geographic Distortion of Position (GDOP) If you take two bearing measurements from positions that are "close" together, you get two lines of bearing that intersect each other at a very acute angle. The Circular Error Probability (CEP) ellipse has a very, very long major axis. You have nothing approaching a firing solution. OK, fly for "a few" minutes. Make another measurement. However, since the problem we are trying to solve is locating an emitter that shuts down quickly, it will probably be gone before you fly far enough to beat the GDOP. It also may well be that the "best" direction to fly takes you into locations that are distinctly "unsafe" for your aircraft.
When one adds in the fact this notional target is a "radar target of opportunity", choosing to prosecute it with a JDAM means you aren't doing your "original" mission. If you are "hunting" radars, you are going to need to fly to where you can see the radar. The JDAM range of 45 km from altitude is well within the range of S-X00 missile systems. You probably cannot survive flying around for minutes trying to get a geolocated solution to program into your "ipad", even if you had a DF system that could do that and software to help you. If you have a HARM, launch it and get out of Dodge or get low enough you can't "see" the radar on your RWR any more.
There are sigint aircraft that do have "precision" DF systems that can geolocate radars. These aircraft fly in areas where they are "safe" from threats (they hope), so they can stay there for a long time. Radars can shut down and come back on later. These aircraft have software that processes the many thousands of LOBs collected and "makes sense" of a lot of them, yielding good targeting solutions. These solutions are available (at least to US consumers) in time frames from hours to a day or so, depending.This is very "old" technology, but it works. The US also has high-flying elint drones that can do precision DF measurements. These drones use antenna technologies that have been perfected for this task. The data is uplinked and can be used to geolocate "pop up" targets relatively quickly. The drone may take a while to fly far enough to beat the GDOP, but generally it isn't going to get shot down, we hope. It also can fly over hostile territory more easily. If it gets targeted, it is much less of a loss than an RC-135. The P-8 also contains systems that can do a similar task. Presumably Ukraine has access to much of this capability.
It should be noted that the best way to geolocate emitting targets in today's world is almost always NOT "triangulation". There are other methods, including some "old" ones (TDOA) that work well and don't require LOBs. Nearly all these methods involve flying some distance in order to generate a good "solution" and they work better if the aircraft maneuvers while doing so. These approaches mostly don't require a LOB measurement as such. This turns out to be a big advantage as it removes lots of physical limitations on the antennas. An example can be found here, but it is one of many. https://apps.dtic.mil/sti/tr/pdf/ADA452783.pdf In so far as I know, this particular research never led to a deployed system, but other similar ones have.
It also should be noted that if several sensors make simultaneous measurements of the same emitter at different geographic locations very accurate emitter location is possible. It can be done "after the fact" by post-mission processing of data collected from different platforms. It can also be done in "real time" by consumers who receive all the data via a satellite link or other means. This includes the various "sensors" themselves. It also should be noted that the F-35 has the capability to do this sort of thing, both as a sensor and as a consumer. It also has the ability to persist in a high threat airspace much longer that any SU-24 can. All that money did indeed buy us something :-).
Obviously, Ukraine has no F-35s, but there is no reason they can't have sigint aircraft of their own if they need them and it is a high enough priority. The equipment required to do it is mostly available COTS and that which isn't is easily within Ukraine's ability to procure from defense contractors. This makes much more sense and bang for the buck than trying to hang an ESM system on a MIG.