Extra ring shown on passive sensor detection range display

[DoktorV (OP)]

I understand the formula for calculating the detection range of a passive sensor against a given emission strength, but I get conflicting displays on the system map.

I have a DSTS array rated at 3600.  Against an emission strength 220 object, it should have a maximum detection range of 3600*220 / 1000 = 792 Mkm, and there is indeed a blue ring at that distance.  However, there is also another ring displayed way way out there, at a radius of ~19. 2 Bkm.  What does this second ring mean? The arithmetic suggests that it indicates the detection range against an emission 5333 object, but why is it there?

[Erik L]

Passives? EM or Thermal?

[DoktorV (OP)]

I was referring to tracking station installations, which I believe count as both EM and thermal sensors and operate on the passive sensor formula.

[MarcAFK]

I've seen this also but I think I had resolved the issue, I can't remember what I determined though.

[jseah]

Was it red colour?

That could be a transponder detection range. 

[ollobrains]

sounds like a transponder beacon if its red

[DoktorV (OP)]

The extra ring is not red, it's the same blue as the passive detection range circle.