Only rarely--and I dare say NEVER--has an attacking ship ever locked onto another vessel that didn't already know it was there.
Yet the victim can always tell that "They have locked weapons on us!". He shouldn't.
Obviously, active targeting is in use in Trek. But that doesn't mean passive targeting wouldn't work, or that it shouldn't be used...
If you can identify a situation in the entirety of Star Trek where passive targeting would have been in any way advantageous, you would have a point. As it stands, the only one that comes to mind is Worf "manually" aiming the Bortas' disruptors in "Redemption pt1" so the Duras ships won't have time to re-raise their shields; you could call this an example of passive targeting, but the implication is that manual targeting is difficult enough that only Worf is good enough to pull it off.
The active beam gives you PRECISE measurements of the enemy's course and speed while passive targeting can only give estimates, with the weapons officer having to make up the difference.
For the same reason you can't accurately measure things with a ruler that has no tick marks. An active sensor can control variables like doppler shift and polarity, and besides that can send out a sufficiently strong signal that can separate a positive return from noise. Passive detection has alot of variables your computer can't completely eliminate, and the signal input is weak enough that noise has to be factored in too.
Really, it's the difference between eaves dropping on a conversation and asking someone a direct question. You can only extract so much information from listening in the background.
Hardly. Indeed, if the range is long, that's where terminal guidance becomes the most urgently needed... Typically, an anti-aircraft missile might be fired at a target half a Siberia away, on inertial guidance, and would then use radar at the destination to compensate for the target's evasive action.
Which isn't a purely fire-and-forget weapon, especially against a moving target. Modern anti-ship missiles require midcourse correction at those extended ranges; in fire-and-forget mode, most of them have MUCH shorter ranges.
Becuse an omnidirectional lens can see everything, but cannot analyze anything; in that kind of broad-field scan it shows up simply as an anomalous flash of light from which little other information can be obtained; if you want to actually identify the thing as a Klingon bird of prey, that requires actually focussing on that portion of the field enough to resolve fine details;
you have to look directly at it.
Infinite focus in infinite directions is a type of sensory omniscience which starships have never consistently demonstrated; the inconsistency (where they sometimes DO seem to see everything around them, no matter how small) can be interpreted as some such system "getting lucky" with random searches of a particular narrow quadrant at the exact moment a phenomenon happens to appear.
There would be no difference between passive and active sensors in this respect. So it's just a matter of how quickly your weapons can react to the cues given by the targeting system.
Indeed. The problem is a passive targeting system wouldn't give you those clues even if he was visible; your tactical office would have to take a guess and hope he hits him.
Well, EM is EM. Only wavelength matters.
Not really. Depending on the materials you have available, some frequencies are easier to focus than others, and are therefore much more useful at a specific range or for a specific purpose. LIDAR and milimeter-wave radars give you much finer returns, so can give you a hyper-accurate targeting solution. But they're not very useful in a wide-field search for precisely this reason: the thing your looking for has to be MUCH larger for you to pick it out of the usual signal noise. A "blurry" image produced by a longer wavelength radar makes it easier to get a nonspecific "there's something out there" reading and then focus your more precise sensors on that spot.
Visual can be useful for targeting, but at a long enough range you wind up mounting the Hubble Telescope to your phaser emitters just to target the enemy.
That, and the fact that in the visual range and close to it, there are external sources of EM so passive sensors can work even when the target is being wewy wewy quiet.
Infrared doesn't need an external source, and neither do some microwave frequencies.
True, but they won't be able to target the gun turrets or the missile launchers specifically that way. An imaging microwave radar would allow them to do that, but very few weapons so far use microwave radars that way.
Some versions of the Hellfire use milimeter-wave radar to target tanks and ground vehicles.
Imaging IR is a more popular way, and essentially means passive visual EM,
No, IN PRACTICE it means manually designating a specific aiming point and then painting a target on that aiming point with a laser beam; you then fire a small missile programmed to home in on the reflection from that laser beam and blow the crap out of it. This is called "semi-active" since the active portion of the lock is coming from the launcher, not the weapon itself.
visual spectrum guidance (i.e. image recognition technology) is already less reliable than radar guidance for a variety of reasons.
"Already"? I'd say "still". Image recognition is a matter of getting better computers to better utilize the inherently superior qualities of the short wavelength ranges...
It didn't used to be. The first reliable ground-attack missiles used IMRC guidance to track targets using an eliminate-the-difference algorithm, and the most reliable anti-aircraft missile for many years was the IR-guided Sidewinder. The famous Maverick missile now uses infrared, as does the Walleye bomb. The TLAM Tomhawk used image recognition and image scanning for guidance as well as targeting.
All of these systems have become less accurate than missiles using millimeter-wave and microwave frequencies, which have a much better signal to noise ratio and are harder to confuse with camouflage and evasive action.
To be sure, much of that tracking is in fact done by passive visual EM.
Of asteroids, sure. Space debris, not so much; the many thousands of objects tracked on a day to day basis are invariably monitored by radar stations, not telescopes.
And it's a matter of tracking objects against nothingness. A technique that's good enough for that doesn't necessarily allow one to target the enemy's phaser banks, which was the big point in favor of passive visual EM.
This assumes you can be sure that you know what the enemy's phaser banks look like, and that isn't always a given. It also assumes that your passive scan can provide pinpoint accuracy on the position of the enemy ship, let alone a particular aiming point on that ship; again, it usually can't, which is the entire purpose of using phaser locks in the first place. You paint a target on your enemy exactly where you want the shot to go; you can't miss. If this isn't an option, you can MANUALLY aim the weapons to hit a particular target, and while this is entirely possible (sharpshooters have been doing it for 3000 years) it can't be done by computer.
