I know there are 4. They are for 360degree real time coverage. But Gökdeniz at the back of the frigate so rear panels are useless.
2 plates could give 180 degree realtime coverage for Gökdeniz which positioned at the back.
Usage of Mar-d on gökdeniz which is located on i class looks like it isn’t meant for gökdeniz.
In my opinion (also many experts have same) for air defence engagements our barbaros mlu's and istif's don’t have enough sensor capability. Just because changeing mode smart-s mk2 to more accurate for missile engagment create a great gap the long range search capability of ship. Ship needs a more accurate second radar (x band) for seeking aerial targets in siper-hisar ranges. Also we will hopefully give a guidance support to missile until midcourse with akr-d b2 fcr. So Mar-d with 100-120 km range and x band capability create a great secondery x band radar for ship. Like Çafrad-Umr/Çafrad-çfr just more basic and limited version.
On the other hand aesa radar panels on gürz is not special for gürz. you can see same radar panels in hisar-d rf ship based fire control system project. İf you look last aselsan magazine page 147 looks like we will see same panels on istif class and maybe barbaros mlu.
But yes on gürz also have akr radar for fcr. Most probably, aesa panels will be used for search radar for gürz and fire control radar for hisar-d rf. (aesa panels are very multicapable things.)
And last with all of this idea , if I must give an answer to ; why locating of mar-d in istanbul on the gökdeniz when compared mlu more diffrent position ? Gökdeniz on barbaros mlu is front of the ships so there are already coverage area of smart-s mk2 radar. You need to separate radar from system. But on to istif class gökdeniz on the behind. There are no coverage problems. Mar-d already on the gökdeniz ecosystem and can work independent power source.