I agree these three pictures show the seeker of the PL-15E with the first and third one showing the back side of the mounting plate with and without the modules and the middle picture showing the front with no radiating elements attached but this picture does not match up with either the front or the back of the seeker. I'm still not convinced that the PL-15E has over 600 TRMs in it, that's an insane amount of TRMs that you crammed into an 8 inch diameter antenna and scaling up to a fighter sized 1 meter diameter antenna that'll mean such an antenna would have over 15000 TRMs even if we account into the fact that X band TRMs would be of a larger size that's still a ridiculous amount of TRMs.
View attachment 151991
Phased array radiator spacing is typically around 1/2 wavelength, could be larger or down to 1/4 wave but 1/2 is optimal.
Ku band wavelength is around 16mm, 16/2 = 8mm, PL-15 diameter is ~200mm, 200 / 8 = 25, which is pretty close to the picture.
Fighter X-band arrays has x2 the wavelength compared Ku band, so element spacing would be x2 as well.
The number of elements is actually one of the stronger evidence for this picture being from PL-15