Tie it to the passive sensors mechanics instead; you need to close a certain amount of distance relative to the max range of the passive sensor for a (to be determined) amount of signal strength to meet thresholds for how good your data is and how fast you get it (very long range scanning gets you very rough estimates very slowly, while close in scanning gets you very good information very quickly).
Use thermal passive sensors for information on industrial outputs like mining and construction and maybe some estimate of population size, and electronic passive sensors for everything else.
Well SIGINT (Signal Intelligence) we need to separate between communications and non communications. COMINT entails listening in on the enemy communications to learn their secrets rather then simply scanning their ships or the analyzing emissions from ship systems (ELINT). This means you also need to have translated their language and (if sensitive information) also cracked their encryption/codes.
For the other sensors currently we got for example the following Intelligence already in VB6:
Active GRAV: Target Size, Target Speed, Target Direction
Passive GRAV: Emissions from shields or Active GRAV. Emissions from population.
Passive TH: Emissions from engines. Emissions from population.
Perhaps this could be expanded by saying that if you get good enough sensors to be X times better then what you need for them to show up on sensors you learn more ( potentially in multiple tiers ), and this would naturally also require much longer observation times then 5 seconds.
For example something like this:
Active GRAV > 10 times: Target Type (Military/Civilian), Target mission ( main tonnage is Carrier/Sensor/Missile Warship/Beam Warship/Logistics/Colony/Terraform/Salvage )
Passive GRAV > 10 times: Shield Strength or Active GRAV sensor strength & resolution. More details from population.
Passive TH > 10 times: Match signature from engines (can determine based on previous salvaged/detail scanned). More details from population.
Active GRAV > 100 times: External systems count & type ( X launchers, Y turrets, Z engines ... )
Passive GRAV > 100 times: Full shield design details or Full Active GRAV sensor design details. Most details from population.
Passive TH > 100 times: Full Engine design details. Most details from population.
Active GRAV > 1000 times: Full Weapons design details
*With "Full design details" I mean the knowledge of the design, not the tech to produce it yourself.
This information would automatically be added to appropriate intelligence tabs.