Sensors
Sensors
The term sensor describes a whole range of complex devices that detect and analyze many forms of data—light, radio and other electromagnetic emissions; sound, motion and vibration; gravitational, nuclear and magnetic fields; heat, pressure and trace chemicals; and even other sensors. Essentially, anything that enhances a person's ability to receive data about their environment—from macrobinoculars to radiation counters to radar to long-range electromagnetic flux detectors—is a sensor.
While the majority of ships use sensors for peaceful purposes—navigation, collision avoidance, research, and exploration—the current Rebellion and the rise of piracy in many outlying systems is forcing many ships to purchase new sensors or reconfigure their existing ones to be combat-quality.
The most important task by far for military sensors is ship detection. Considering the massive punch warships pack, quite often the first shot in a battle decides the winner. To find each other, ships use sensors which scan for heat, electromagnetic energy, gravitational disturbance, motion, radio waves, light refraction, and more.
Many sensors analyze a broad spectrum of data from several sensing inputs; others focus on particular types of energy, fields, or objects. Sensor ranges vary from short (a few kilometers) to extremely long (up to one million kilometers), with specialized sensors usually having greater range. Because of size and computer limitations, smaller starfighters must usually rely upon broad-range sensors; larger ships have many different specialized sensors.
While this usually gives the sensing edge to larger vessels, it's not all that simple. Large vessels are bigger targets: they radiate more energy, they reflect more light, and they cause more gravitational disturbances. As an analogy, while a rancor may have a better sense of hearing than you do, you are as likely to hear it crashing through the woods as it is you.
Common Military Sensor Types
Thousands of different sensors exist. Naturally, some are more sensitive than others. None are perfect; even the best sensors can fail to detect when they should, or can detect "ghost" images that don't really exist. Solar radiation, hydrogen clouds, asteroid fields, strong gravity wells, and other natural phenomena can interfere with—or even block—sensors. Of course, deliberate jamming or concealment can also hide things from sensors.
Below is a list of some of the more common sensor types:
Electro Photo Receptors (EPRs)
These are the simplest sensing devices. They combine data from sophisticated normal light, ultraviolet (UV), and infrared (IR) telescopes to form a composite holo or two-dimensional picture. Useful only at shorter ranges. Most targeting sensors use EPRs.
Full-Spectrum Transceivers (FSTs)
FSTs are frequently called "universal sensors" because they use a variety of scanners to detect all types of objects, energies and fields—but they are not very sensitive. The size of their receptor determines their effectiveness; receptor dishes must be quite large to detect accurately or at long range. Most non-combat ships are equipped only with FSTs.
Dedicated Energy Receptors (DERs)
DERs detect any electromagnetic emission within range of the sensor array, including comlink transmissions, navigational beacons, heat, laser light, and similar emissions. The DER's accuracy is determined by the skill of the operator, whether person or computer: as DERs collect all energy emissions, sorting out the important information from useless data is crucial. A poor operator could mistakenly identify a stray cosmic ray as a brief enemy communication signal; an expert operator may filter through a screen of static to uncover the signature of a ship trying to sneak by. DERs are the primary passive sensor device in military sensor arrays.
Crystal Gravfield Traps (CGTs)
These expensive sensors utilize a synthetic crystal grid to detect gravitic field fluctuations. High quality CGTs can detect and identify any fluctuations in the gravity field for hundreds of thousands of kilometers around.
CGTs can be blocked by the presence of mass. For example, a CGT will strongly register a nearby planet's presence, but may miss a ship in orbit on the other side of the planet.
Hyperwave Signal Interceptors (HSIs)
These sensors detect fluctuations in hyperspace. Whenever a ship enters or exits hyperspace, the local hyperspace field is disturbed—the mass and speed of the vessel determining the size of the disturbance. Ships nearby carrying HSIs can detect the disturbance. HSIs cannot determine a ship's origin or destination, but they can record the entry to or exit from hyperspace.
In addition to detecting ships moving in and out of hyperspace, HSIs can detect and sometimes tap into hyperradio transmissions (such as those sent by HoloNet or subspace radio). This is important since most hyperradio communications are broadcast on very narrow bandwidths and are normally very difficult to detect. Decoding such messages is another matter entirely.
Life Form Indicators (LFIs)
LFIs aren't actually sensors; they are sophisticated computer programs which examine the output of other sensors to determine if a life form is present, and, if so, what life form it is.
For example, an FST sensor might determine that there is a mobile heat-source (outputting heat at 30 degrees Celsius) on that ship, the source masses at 80 kilograms, the ship's atmosphere contains large amounts of sulfur, and the ship's gravity is set at .96 Standard; an LFI program would examine that data and decide that the ship probably contained a Sullustan.
The quality of a ship's LFI is determined by the sensitivity of the ship's sensors and the intelligence of its computer.
Sensor Countermeasures
Jamming Sensors
Jamming is the most common active countermeasure. Powerful generators can flood large areas with static and random signals, confusing and "blinding" sensors. One drawback to jamming is that while the exact position of the jamming vessel may be concealed by the jamming, the jammer is broadcasting their general location to everybody in the area. In addition, jamming affects everyone—friend as well as foe.
Sensor Decoys
Ships can fool enemy sensors by sending out small pods or shuttles which broadcast the same signals a large ship emits naturally. Only exceptionally sensitive sensors can tell the difference between a good decoy and a real ship.
Sensor Stealth
By purposefully reducing all emissions, ships can greatly reduce the chance of discovery. Turning off the engines and drifting is often the first and most effective evasion technique. Ships drifting on battery or power capacitors are far less likely to be detected, but of course can't operate long without turning on power generators for life support.
Ships trying to evade detection can also shut down their active sensors. Although this makes them much harder to detect, it also leaves them blind.
"Running silent" is a standard technique; while on patrol or otherwise attempting to remain undetected, ships send no transmissions. Communication blackouts are difficult to maintain when several ships are operating together, since course, timing, and mission changes must be transmitted between the vessels.
Sensor Modes
Passive
Passive sensors examine energy emitted by other sources (heat detectors, or simple telescopes, for example). They don't project any energies to detect information. Less effective than active sensors, passive sensors use less energy and don't increase the sensing unit's "visibility."
Sensor Sweeps
These sensors are active and emit pulses of energy and examine the reflected or "bounced" energy (radar, for example). Extremely effective at short and medium range, less so at long range. Because the sensor is giving off controlled bursts of energy, the sensing vessel is relatively easy to spot by other sensors.
There are three prime modes of sensor sweep: scan, search, and focus.
Scan
Look at everything around the entire vessel. These sensors search the entire area around the vessel, but cannot provide the range or detailed information of sensors in search mode.
Search
Only look for a specific type of target, such as a ship or a particular radio frequency. The operator must specify what to search for. Search modes function in one direction (for example, to the front, left, right or back). Sensor modes "warp," so while scanning "left," the sensor also searches to the top and bottom of the left portion of the ship.
When several ships fly in formation, pilots often "search" their sensors on overlapping areas. For example, the lead pilot may focus sensors directly ahead, while other pilots in the wing focus to each side and behind.
Focus
Concentrate the sensors on a particular area selected by the pilot. This makes for much better information about the area on which sensors are focused, but provides little or no information about other areas. This mode is often used once something "unusual" has been detected by more general sensor sweeps.
Cloaking Device
The ultimate sensor countermeasure, a cloaking device is an experimental shield which creates a subtle warp in the fabric of space surrounding the vessel, causing all forms of energy to slip around the ship as if it weren't there, making the ship practically invisible. Exact specifications and technical data of cloaking devices are among the most highly-classified in the Empire.
Cloaking devices are extremely rare. They are among the most sophisticated and complicated devices known; only a few highly skilled engineers can operate and maintain them. They are not in general production: each must be custom built for a specific ship.
In addition, cloaking devices are enormously expensive—reportedly over one billion credits apiece.
The Empire has declared cloaking devices illegal—class one contraband. Unauthorized manufacture, sale, purchase, or use of a cloaking device are crimes punishable by death.
Because of the expense and difficulty of maintenance, very few Imperial ships are equipped with cloaking devices. It is rumored that the Emperor's personal shuttle has one, and possibly a new experimental Star Destroyer.
No Rebel ships are known to be equipped with cloaking devices.
Source: REUP:418