US-made weapons augmented by Global Positioning System (GPS) satellites for position updates in Ukraine are now susceptible to Russian electronic warfare (EW) jamming ... The weapons affected may include the 155mm Excalibur artillery projectiles, Ground Launched Small Diameter Bomb (GLSDB), Joint Direct Attack Munition (JDAM) and weapons rounds used with the High Mobility Artillery Rocket System (HIMARS), among others, depending on how they are employed by the weapons operators.
An unnamed source reportedly familiar with the classified report told the NYT that in the worst-case scenario, only one in 19 Excalibur rounds was hitting its target, where the report said the cost per successful strike skyrocketed from $300,000 to $1.9 million between January and August 2023.
Being able to test GPS jamming techniques against intact munitions isn't some hypothetical academic problem.