I calculated correctly with the EM I just brainfarted and used size instead of sensitivity... 
As for lighting up that is a none issue as you are using such sensor craft to put active sensor on an already detected enemy... and a cheap one at that. You could use multiple sensor scouts at multiple vectors and only light them up briefly before turning of the sensor and move to another position. All the while missiles are inbound. Given how small and stealthy (reduced thermal engines are easy to give these) they are it is very hard to find them once their sensor is off.
And how do you know they are not a cheap bait for your interceptors...
Given how small and cheap they are it is efficient.
I agree that passive sensor are more important as finding the enemy before you are found yourself is key.
But these really small sensor crafts will be efficient in that they are stealth when they turn the sensor off. An active only need to be on for a few seconds to get data.., you don't run around with them on all the time. Even a small escort could have many such small scouts to send out in active patrols instead or as complement to passive scouting.
Since they are smaller than 50 ton they will be really hard to engage as they are very hard to find. It will also be very cheap with stealthy engines o such small ships so they are very hard to find on thermal sensors too.
You'll need so many of them that it'll be inefficient. For painting a fleet when you already know it's exact position, sure, it might be useful to have lots of tiny scouts, but they're never going to keep up with any serious battlefleet because they're going to end up with minimal speed and endurance. Which is pretty much the exact opposite of what you wan for reconnaissance or patrol activities.
Flicking on the active sensors momentarily doesn't mean that an opponent in range won't see the EM surge and investigate. A gunship with reduced-size gauss cannons and reasonably boosted engines is both very inexpensive and hard to counter without defensive assets that will end up presenting a larger target to track, and can be reasonably expected to get close enough that subsequent pulses will paint a bright red target on the scout. A moderately-sized fleet can easily carry dozens of these things. Even bog-standard railgun PD fighters can be easily re-purposed to go scout hunting in a pinch.
And how exactly do you expect to maintain continuous sensor coverage from multiple vectors on a target that will certainly be random-walking itself, and will also be able to see your sensor from maybe twice it's own range? You're assuming that these scouts can effectively surround a likely faster and more endurant enemy, and will know exactly when they are in range so they can activate their actives at the exact same time. They're also going to be completely useless against smaller vessels.
Here's how this will go. You launch fifty of these scout boats and manoeuvre them into place. Combined, they can search an area of
74,753 quadrillion square kilometres. Except that's a circle with a radius of about one AU. Oops? You are absolutely not going to be able to find a hostile vessel hidden in any moderately-sized star system by running around blind with only moments of sensor coverage. Not before it sees you first, and avoids you or guns you down.
With how much C# will increase fog-of-war, running down any long-endurance enemy ghost fleets in a system is going to be an utter nightmare. Clearing systems is going to be very, very painful for an attacker and you can never quite be sure there won't be a minefield suddenly appearing amongst your convoy routes.
I have done this MANY times in the current version of Auroa as well... these small scouts are generally faster, some times much faster than larger ships. They are often relatively short range though and even shorter range in C#.
These small sensors are way more efficient than a comparable larger sensor so you can have more of them. That is the whole purpose of the new change to the system as you need to quadruple the size of the sensor to scan twice as far.
You keep continuous sensor coverage with using a few scouts that paint the target in turns if necessary, long enough for missile strikes to hit. About 20 million km is a pretty far distance for such a small craft. Even loosing one or two will make little impact on your ability to scout.
And yes, small scouts are very likely to be much faster than a standard warship, at least in the context I usually see them as they trade speed for range. As they are launched from a carrier they don't need efficient engines or endurance. A 10t 2-3x engine on a 30-35t craft will make it go really fast. These scouts are NOT long range or endurance ships. They are small fast scouts with a specific purpose, speed and stealth are their defences.
If a fleet start seeing pings of dozens of small scouts in an area they can certainly avoid that area, that can also be the intention when you then funnel an enemy into a different area where you placed your passive scouts. They don't need to cover an area fully either as no sane admiral would fly their capital ships in the general direction and risk being detected as you don't know where the scouts are or will be. So a handful of scouts would be able to cover a pretty large area by making random searches here and there. It might also be a trap to go after them as well, how do you know?!?
Is it worth the risk destroying an extremely cheap little 30-35t scout and risk loosing something way more expensive.
You also DON'T search in squares or circles, the whole purpose with more space efficient sensors is that you search in LINES or at least layered lines, that means a small sensor are four times more effective than comparable large sensors if they are all of the same speed. I really don't understand why you would scan an entire system like this, this is a tactical tool not a strategical. It is for when you know the general area of an opponent, these scouts don't replace passive scouts, buoys, stations or ships. They are a tactical tool with a specific use. Why do you assume they are used in the attack role... I don't think it matters if they are used offensively or defensively.
There are many fun ways they could be used with other assets.
So, the reason I asked for lower resolution sensors was that you could more easily paint such craft from a distance and shoot them down with small AMM like missiles. In the current form the only option is more or less a beam interceptor. The smallest beam interceptor are likely to be at least about 75-100 ton or so as the smallest Gauss is 25t for the weapon itself and then you need a fire-control, engine, fuel etc.
Against the AI all these points are moot as they will clearly be OP against the AI no matter what, even more so than in VB6 Aurora. I'm talking about multi-faction games where several sides are human controlled.
