The design of the Intrepid was off, the rear facing communications/sensor dish was bizzare and they needed to explain with technobabble what advantages it has.
It makes alot of sense if you're the sole vessel at the perimeter of your borders scanning Long Range.
Normally, it's the Main Deflector Dish that is used to scan at Long Range.
Think of your Deflector Dish as analogous to a Focused Beam Flashlight without much spill off to any side.
In a Spherical 3D environment like space, it takes a few seconds standing still to scan everything within a cone at full detail at long range before you rotate your vessel to scan everything within the next arc section of your sphere. Eventually it does take a few minutes to scan all areas of the sky by slowly rotating your ship around.
With a secondary Long Range scanner working in conjunction, it would take half the time since you're covering Fore & Aft simultaneously.
It's also good for traveling to make sure nobody is trying to sneak up on you at long range when moving forward at STL or FTL.
Deflector Dishes have also been used as "Make-Shift" Beam/Exotic Energy emitters on occaision. It would always be good to have a "Back-Up" Deflector Dish if the main Dish goes down for whatever reason.
Then there's the fact that sometimes, the Deflector Dish is used to erect the Shield Bubble around the vessel, if you have a backup Deflector Dish facing aft, you could have 2x Shield Bubble emission sources that are totally seperate for each other.
Remember that nice little feature of the Nova Class where it takes 45-seconds to charge the main Deflector Shield to 100% Shield Capacity, but you have to turn the shield-off to rapid recharge, now imagine that with 2x Deflector Shields.
If you had 2x Deflector Dishes of equivalent strength or somewhat close, you can alternate where one is off and re-charging, while the other is on in it's place.
The enemy/opponent would need to have enough fire-power to blast through 100% of your shields in under 45-seconds of combat for both shields to truly penetrate your defenses.
Add that to the Contour-Hull hugging Skin Shields, you could have "Many Shield Emitter Sources" where only one is active at any given time, but you turn on/off which shield emitter system you want and you can buy time for shield systems to recharge while you rotate shield systems.
Effectively having shields permanently on with only a split second to swap between shield units.
There's all sorts of benefits to having multiple Deflector Dishes.
If you had more advanced shielding systems, you could have the Bubble Shield active on top of the Contour-Hull hugging Skin Shields, effectively having Two layers of shielding up at any given time.
So if one energy blast somehow has damage that bypasses or partially bleeds through the outter layer, the inner layer can take-up the slack.
The down-sides to having all this extra tech is you need to design the ship around it and have extra reactor energy output capacity and backup battery systems to make it all work, effectively making your ship bulkier & larger to do it.
