Star Trek: Federation Sensors
Last Revised: 1999.01.10
Federation sensors are entirely based on subspace, much like the ancient subspace sensors used in our galaxy over 25,000 years ago, during the time of Xim the Despot (ref. Han Solo and the Lost Legacy). This indicates that their sensor technology is markedly inferior to our own (as with other aspects of their technology, it is based on technology that we possessed eons ago). As for specifics about their sensor tactical capabilities, the TM states that both EM and subspace sensors are used to track targets (pg. 126) and we know that if the EM sensors are not functioning, the computer is unable to lock onto targets.
Federation cultists claim that subspace sensors were used for targeting in Redemption and Shattered Mirror among other occasions, but they neglect to mention the fact that at no time in these episodes was it stated that the subspace sensors were used exclusively, without assistance from other sensors. In Balance of Terror, they were unable to use their EM sensors because of the Romulan cloaking device so they had to rely on subspace sensors alone. In this situation, their command crew was forced to "blanket" the target area because the subspace sensors were not accurate enough to lock onto a target.
There is further evidence that subspace sensors are not accurate enough to detect starships without the aid of EM sensors: in The Gambit, Chief Engineer Laforge said "Data, I know this is a longshot but if I remodulate the long-range sensor array, I might be able to make it sensitive enough to detect a ship", whereupon Data told him that it would never work. The long-range sensor array of a GCS is its subspace sensor array, which was clearly not capable of detecting ships based on the fact that Laforge hoped to be able to modify it to give it this ability, as well as the fact that Data said it would never work. This type of dialogue is not hearsay; they made important decisions based on these statements.
The Picard Maneuver works because it fools EM sensors into thinking that there are two separate ships, but this would simply not occur if starships could use subspace sensors exclusively for targeting.
The cultists claim that the Ferengi could not track the Stargazer at warp because they did not possess subspace sensors, but this is an extremely weak assertion. For one thing, it would be impossible for a warp-capable ship to navigate safely without subspace sensors. Also, this explanation fails to explain why the Enterprise-D couldn't simply use its subspace sensors to track the Stargazer in "The Battle" rather than reconfiguring its sensors to track deep-space gas compression ahead of the Stargazer. It would have been far simpler to lock onto the Stargazer itself, if it were possible to do so.
Therefore, at short range the EM sensors and the subspace sensors combine to provide accurate information for a phaser-lock. At long range, the subspace sensors provide enough location information for a photon torpedo launch. And both long and short ranges, the subspace sensors prevent an enemy from completely slipping out of detection range even at high warp.
There are numerous circumstances under which sensors cannot function:
The Wounded: establishes that sensors are unable to penetrate a high-energy subspace field.
Captive Pursuit: establishes that the duranium access tunnels on DS9 are impervious to sensors. Duranium is a naturally occuring ore in planetary crusts such as the crust of Bajor (ref. DS9 TM), and we know that duranium-235 is used in phaser arrays (ref. TM). Therefore, duranium is most likely a modified name for uranium- this indicates that dense metals can block sensors. Starships can be scanned in spite of the duranium in their hulls, but they use a duranium/tritanium composite (ref. TM). If tritanium is simply a modified form of titanium (see Federation special-tech), then this is logical- titanium is much less dense than uranium, so a tritanium/duranium composite would be much less dense than pure duranium.Duranium is a common component of starship design and construction and we know that starships can be scanned in spite of the duranium in their hulls, so the duranium on DS9 must have been more dense or thick than the duranium in starship hulls. The fact that duranium (a high atomic-number element discovered sometime after their 20th century) completely blocks sensor scans indicates that Federation sensors can be defeated by using high-density materials.
The Doomsday Machine: establishes that the Enterprise cannot scan through the neutronium hull of the planet-killer.
Descent Part 2: establishes that non-lethal levels of ambient EM radiation can interfere with sensor operation. Unusual EM fields emanating from Lore's Borg enclave planet interfere with the Enterprise-D's sensors, to the point that they cannot locate away teams on the surface. Note that these EM fields were not strong enough to affect the humans and Borg drones moving around on the planet's surface.
Remarkably, in spite of the extensive research the Federation has put into their sensor technology, they have no facilities whatsoever for detecting cloaked ships. Their only successful detection of cloaked ships occurred during the Klingon Civil War as seen in "Redemption Part 2", when a network of starships used tachyon streams in a manner similar to 20th century laser networks, to detect cloaked Romulan Warbirds. This technique is extremely wasteful of starships and it is totally ineffective without prior knowledge of the enemy's approximate location. It is ironic that in spite of the massive (and tactically pointless) scientific data-gathering sensor suites aboard their starships, they lack a particular type of sensor technology (crystal gravfield traps) which would actually be tactically useful.
The Federation tends to install large arrays of scientific data-gathering equipment on their ships, but this should not affect the tactical balance since long-range scientific data-gathering is interesting but not tactically useful. Their sensors are based on technology which we possessed 25,000 years ago, and they lack the ability to detect cloaked ships without using ridiculous work-arounds like tachyon-stream networks. Therefore, they must not possess an equivalent to crystal gravfield trap sensor technology. Our sensors achieve equal or superior performance in all tactically significant areas (although they may have more on-board equipment for "cataloguing gaseous anomalies" and other tactically useless functions), and we can detect cloaked ships if necessary, with CGT sensors. We do not predict that sensor technology will have any significant impact on our planned campaign against this Federation.