From Aviation Week
It wasn’t hard for the Russians to assess the JSF’s stealth performance. By 1995, everyone knew that shape was the major driver of RCS, with materials being used to control local scattering phenomena. As the JSF’s target service entry date arrived, so did the Russian answer, and it was on display at the MAKS air show, held in Moscow in August.
The 55Zh6ME radar complex addresses many of the limitations of the old VHF radars. Although you see three radars—stepping down from VHF (metric) to L-band (decametric) and S-band (centimetric)—the Russians call them modules of an integrated radar system. Each unit is fitted with the Orientir satellite-navigation system, which provides a very accurate location and north reference. That should make it possible to provide sensor fusion—ensuring that when two or more of the radar units detect a target, it will show up as one in the control center.
The VHF part of the system (see photo) has a P-14-sized, 30-meter-wide antenna, but it folds onto an 8 x 8 truck. The antenna has an active, electronically scanned array, so if it gets a hit on a faint target, the array can dwell on it as the antenna rotates (or swings back and forth for a sector search). At the same time, it will cue its L-band and S-band sisters to focus on the target area like searchlight beams.
Some commentators will look at the Russian brochures, note that the reference ranges are against targets with an RCS of one square meter and observe that stealth aircraft have a far smaller RCS, which they do—in centimetric bands. Giving what was probably the least provocative answer under the circumstances, a Russian engineer notes that the Chinese DF-15 short-range ballistic missile has a 0.002 m2 RCS in X-band, but is a very non-stealthy 0.6 m2 in VHF.
Two exhibitors at MAKS were showing passive RF tracking systems. They are intended to exploit active emissions from the target but do not discriminate. Scattered energy from a radar will work just as well. The U.S. Air Force does have a modern facility for testing such bistatic radar signatures, but it was commissioned after the JSF was designed.
Of course, this sort of analysis relies on unclassified data. As the author himself states.
There may be a universe where it is smart to give your adversaries (or their armorer) 25 years’ notice of exactly how you plan to render their defenses obsolete. We just don’t live there.
instead, we live in a world where one must have faith that a trillion dollar weapons program has been designed correctly. How comforting.