I'll add a bit of info about detection curves, since I worked with those a lot for LWAMI 3.10 development.
The detection curve is for active sensor detection and counterdetection--Radar/ESM and Active sonar/active intercept. Although, I think Nrd matters for the sonar too, and I don't know exactly how Nrd and detection curves interact. EDIT: on second thought, the only sensor detection curve isn't all that important for is probably passive sonar. It probably establishes a "hard-cap" for acoustic sensors and that's it.
Anyways, for the active sensors, the detection curve consists of a series of points on a line, which represents the detection threshold for that sensor. Each point has two values, range and SL (source level). What that point means is that at range X and against a target with SL Y, the sensor will detect the target. If you "connect the dots" of all these points (including 0,0), you will have the detection "curve." Anything inside this curve gets detected, anything outside is not. (Ceteris paribus w/ respect to aspect, weather, etc.)
For counterdetection sensors, it is a little confusing at first but does make sense. The curve represents the ESM/intercepts ability to detect an emitting sensor that would detect an object of SL Y at range X. So the values establishing a weaker detection curve actually increases the sensitivity of the counterdection sensor--it means the passive sensor is sensitive enough to pick up a weaker emission.
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