Franz-Stefan Gady has written an excellent article at the The Diplomat paysite. The article is an interview with Mauro Gilli, a senior researcher in military technology and international security at the Swiss Federal Institute of Technology. The article titled “Mauro Gilli: Selling the F-35 to Countries Operating the S-400 Is a Bad Idea” is dated July 3, 2019. Subscribers can read the full article at
https://thediplomat.com/2019/07/mauro-gilli-selling-the-f-35-to-countries-operating-the-s-400-is-a-bad-idea/. Here is a short snippet:
[Franz-Stefan Gady askes] "How [the Russian S-400 system issue is] related to the sale of the
F-35 aircraft to countries such as Turkey or, perhaps less realistically, India?
[Mauro Gilli's responds] "To use the previous analogy, by possessing both the F-35 as well as the
S-400, Turkey or India could figure out how to change the color of the F-35 from light blue to black, and in part how to change the color of the background from light blue to white. To put it more precisely, stealth technology is aimed at reducing the observability to radars operating at specific angles and at specific frequencies. By modulating the frequencies and angles of operations of multiple S-400 systems, one could find the weak spots of the F-35 and, more important, its unique radar returns. By feeding such data into signal processing software, the chances of detection increases markedly – one country would be able to more accurately ignore false positives and more carefully avoid false negative[s]. In other words, if you know what you are looking for, you can more easily find it."
S-400, Turkey or India could figure out how to change the color of the F-35 from light blue to black, and in part how to change the color of the background from light blue to white. To put it more precisely, stealth technology is aimed at reducing the observability to radars operating at specific angles and at specific frequencies. By modulating the frequencies and angles of operations of multiple S-400 systems, one could find the weak spots of the F-35 and, more important, its unique radar returns. By feeding such data into signal processing software, the chances of detection increases markedly – one country would be able to more accurately ignore false positives and more carefully avoid false negative[s]. In other words, if you know what you are looking for, you can more easily find it."
SEE THE FULL DIPLOMAT ARTICLE
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On July 17, 2019 Al-Monitor.com reported:
The “Trump administration said today it would formally kick Turkey out of the F-35 program after Ankara took delivery of a [S-400] Russian air defense system that could threaten the American fighter’s stealth capabilities.
In a White House statement sent five days after Turkey began taking deliveries of the Moscow-made S-400, [on July 12, 2019] press secretary Stephanie Grisham said the F-35 “cannot coexist with a Russian intelligence collection platform that will be used to learn about its advanced capabilities.”
Pentagon officials had long said the Russian system, which is not compatible with NATO counterparts, could train its powerful radar on any F-35 jet operated by Turkey to uncover its stealth protections....”