[Goose]

The U.S. Air Force is buying add-on seekers designed to give Joint Direct Attack Munition-Extended Range (JDAM-ER) precision-guided bombs supplied to Ukraine the ability to zero in on GPS jammers. In effect, this would turn one of the weapons most impacted by this countermeasure into one used to directly attack it. This follows growing reports that Russian jamming is severely degrading the effectiveness of Western-supplied GPS-guided munitions, including JDAM-ERs.

https://www.twz.com/air/jdam-er-winged-b...to-ukraine

It is indeed gratifying that the USAF is acquiring a home-on-jam capability for the JDAM-ER. Unfortunately the contract gives no information on how many home-on-jam units will be integrated or exactly when (other than the termination date of 1-Oct-2025). This is understandable as part of operational security and the fact much of the contract is CPFF and the deliverables are "undefinitized". However, since these items are not already in inventory and available immediately, it is highly probable delivery is at best many months away and that the resulting package hasn't undergone an opeval. The article points out that SARA provided seekers for a test on the SDB. The lack of a follow-up procurement gives one pause. It may be there was no requirement or that the requirement wasn't high enough priority to be funded. It may also be that the results were not good enough to generate interest to even put in place an evaluation program. One does worry that this procurement will follow a similar track to  the GLSDB. The program was announced with fanfare, all of us got excited, and then the production and testing cycle took about half a year or so. Upon employment, it didn't work. Obviously we need to do something, and this is something. Let's hope the USAF is also following this program and doing all the "rapid OT&E" possible to ensure it will work upon first delivery. Their record in this regard is not stellar.

The cited article's comments about the HARM missile also gives one pause. https://ausairpower.net/API-AGM-88-HARM.html. Note this is from 1998 (last update in 2014) and is not in any way "news". There is no doubt whatsoever that the AGM-88C covers the range.

A dielectric radome covers the fixed dual mode planar spiral high band antenna, which is supplemented by an eight element low band antenna array.

The receiver employs Crystal Video Receiver (CVR) and Superheterodyne techniques, subject to frequency band. Reports indicate that the receiver processor is capable of sorting threat pulse trains in high density environments, from the C through to the J bands (0.5-20 GHz).

1.575 GHz and 1.227 GHz are definitely in band and the 8 element low band antenna and superhet channel are not present as decoration. They got added for several very good reasons. Low band jammers and communication signals was certainly one. It would be legitimate to question how well the HARM is able to target the specific jamming techniques used by Ruissia against GPS at present, but those questions apply equally to any notional new system. Russia may also have "reserve modes" we haven't seen yet but homing on such signals is what HARM is already designed to do. Hard to imagine why a new seeker would be required. GPS jamming is not hard to find. At least we can test HARMs against replicas of the Russian jamming waveforms right now, today.

Given that Ukraine has HARM missiles, one wonders why we haven't heard at least something about their employment against GPS jammers, good or bad. I can't explain this. We certainly learned about the GLSDBs, although not in "real time". It might be the HARMs (and JDAM-ERs with HOJ packages) are being reserved for F-16 usage.

[Goose]

The U.S. Air Force is buying add-on seekers designed to give Joint Direct Attack Munition-Extended Range (JDAM-ER) precision-guided bombs supplied to Ukraine the ability to zero in on GPS jammers. In effect, this would turn one of the weapons most impacted by this countermeasure into one used to directly attack it. This follows growing reports that Russian jamming is severely degrading the effectiveness of Western-supplied GPS-guided munitions, including JDAM-ERs.

https://www.twz.com/air/jdam-er-winged-b...to-ukraine

It is indeed gratifying that the USAF is acquiring a home-on-jam capability for the JDAM-ER. Unfortunately the contract gives no information on how many home-on-jam units will be integrated or exactly when (other than the termination date of 1-Oct-2025). This is understandable as part of operational security and the fact much of the contract is CPFF and the deliverables are "undefinitized". However, since these items are not already in inventory and available immediately, it is highly probable delivery is at best many months away and that the resulting package hasn't undergone an opeval. The article points out that SARA provided seekers for a test on the SDB. The lack of a follow-up procurement gives one pause. It may be there was no requirement or that the requirement wasn't high enough priority to be funded. It may also be that the results were not good enough to generate interest to even put in place an evaluation program. One does worry that this procurement will follow a similar track to  the GLSDB. The program was announced with fanfare, all of us got excited, and then the production and testing cycle took about half a year or so. Upon employment, it didn't work. Obviously we need to do something, and this is something. Let's hope the USAF is also following this program and doing all the "rapid OT&E" possible to ensure it will work upon first delivery. Their record in this regard is not stellar.

The cited article's comments about the HARM missile also gives one pause. https://ausairpower.net/API-AGM-88-HARM.html. Note this is from 1998 (last update in 2014) and is not in any way "news". There is no doubt whatsoever that the AGM-88C covers the range.

A dielectric radome covers the fixed dual mode planar spiral high band antenna, which is supplemented by an eight element low band antenna array.

The receiver employs Crystal Video Receiver (CVR) and Superheterodyne techniques, subject to frequency band. Reports indicate that the receiver processor is capable of sorting threat pulse trains in high density environments, from the C through to the J bands (0.5-20 GHz).

1.575 GHz and 1.227 GHz are definitely in band and the 8 element low band antenna and superhet channel are not present as decoration. They got added for several very good reasons. Low band jammers and communication signals was certainly one. It would be legitimate to question how well the HARM is able to target the specific jamming techniques used by Ruissia against GPS at present, but those questions apply equally to any notional new system. Russia may also have "reserve modes" we haven't seen yet but homing on such signals is what HARM is already designed to do. Hard to imagine why a new seeker would be required. GPS jamming is not hard to find. At least we can test HARMs against replicas of the Russian jamming waveforms right now, today.

Given that Ukraine has HARM missiles, one wonders why we haven't heard at least something about their employment against GPS jammers, good or bad. I can't explain this. We certainly learned about the GLSDBs, although not in "real time". It might be the HARMs (and JDAM-ERs with HOJ packages) are being reserved for F-16 usage.