TechMemo:Sensors
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Star Fleet Engineering
Bureau of Starship and Starcraft Technology
Star Fleet Engineering
Technical Memorandum
Stardate: 100324 (24 March 1998)
Editted: 170408
RE: Starship Sensor Systems - General Overview
The sensors used on most starships fall into two major classifications: long range and short range sensors. The terms "long range" and "short range" sensors are somewhat misleading. Short range sensors are capable of observing phenomena occuring very far from the ship and long range sensors are capable of making observations close to the ship. The real distinction is in what can be observed and how it is observed.
Long Range Sensors
Long range sensors are gravitic sensors. They are, therefore, capable of registering distant phenomena "instantly," that is as fast as the computer is capable of processing the sensor data into a useful form. They can determine the mass, position, and a ctual velocity of an object. Gravitic sensors can also detect other gravitational effects such as warp fields, shields, wormholes, blackholes, etc.
While there are other sensors -- including a variety of telescopes which monitor different ranges across the electromagnetic spectrum -- that can collect information over very large distances, they do not produce real-time data because they rely on information which travels at only the speed of light. It is, unfortunately, impossible to push subspace distortions outward to get sensor readings from any substantial distance.
Short Range Sensors
Short range sensors read the electromagnetic spectrum and are, therefore, limited to relaying information at the speed of light (~300,000 km/sec). Thus, if an object is three (3) million kilometers away, the data about the object being scanned by short range sensors is ten (10) seconds old by the time that it reaches the ship. Short range sensors provide enough data to generate visual data on an object. An object "in visual range" is generally considered to be close enough that short range sensor data of the object can be compiled and displayed on the view screen in time for it to be useful in observing the object. Generally, this is considered to be a distance of one light-minute (18 million km). Precise definitions of "visual range" vary depending on the situation. Visual data of a planet, which generally changes very slowly, might be considered useful at five (5) or more light-minutes. However, visual data on a ship moving at half the speed of light (0.5c) might not be very useful if it is more than a few seconds old.
Because electronic countermeasure (ECM) systems have an easy time spoofing gravitic sensors, all targetting sensors for weapon systems are electromagnetic (short range) systems. This is the primary limit on the effective range of weapon systems. Photon torpedoes and other missile weapons are capable of terminal maneuvers towards the target using onboard sensors and maneuvering thrusters. Therefore, they can be launched with a combination of gravitic and older short-range sensor readings. This gives them an effective range of 10 or more light-seconds.
It is possible to collect data from a probe with a FTL transmitter. So starships will often extend the effective range of short range sensors by the use of probes.
