Sensor Rules-Star Wars 3 rd Edition
Nearly ever starship is equipped with at least rudimentary sensors--flying blind would be certain suicide! Sensor systems have two distinct sensor types explained below:
ACTIVE SENSORS: Used by ships and fighters to spot opponents, active sensors operate by sending out a signal in the EM spectrum to bounce off the enemy ship. Despite their great power, active sensors also give away the position of the sensing ship, limiting their use in combat situations. A common Defense Fleet combat tactic involves relying on passive sensors (see passive sensors) sending out scout ships or recon fighters to take active readings and relay them back to the mother ship.
PASSIVE SENSORS: Used to look at the EM spectrum for outputs from the enemy ship. Forms of passive sensing include using your eyes, looking through a telescope or electronically. Other passive sensors can look at different frequencies such as Infrared, the spectrum in which heat radiates.
Both sensor types share the following attributes:
Range: range in Space Units of sensing capability.
Gain: Strength of the sensor, expressed as Die bonus to the Sensor skill.
Resistance: defensive value used against jamming, expressed as a Die value.
When operating the sensors, the sensor operator will roll their sensor skill plus any gain dice the sensor has, plus if using a particular sensor package, add any bonuses that they may provide. The total from that roll is used to detect a particular craft, scan a planet for life forms, or any other data that is desired.
Example: Marka is attempting to find an Imperial scout ship, hidden in a solar system. She uses her active sensors to get a fix on the ship. Active sensors on Marka's ship has Active sensors with a range of 24 Space Units, Gain of +1D, and a Resistance of 1D. She has a sensor skill of 5D plus the gain of the sensors, she rolls 6D, and gets 20. The Imperial ship shows up on her scopes, 15 Space Units away. Unfortunately the Imperial ship now sees Marka.
Example: Marka is attempting to find an Imperial scout ship, hidden in a solar system. She uses her passive sensors to get a fix on that ship. Passive sensors on Marka's ship have a range of 5 Space Units, Gain of +1D and a Resistance of 2D. She has a sensor skill of 5D plus the gain of the sensors. She rolls 6D and gets a 20. The ship doesn't show up on her scopes, but she doesn't show up on any Imperial scopes either.
SENSOR PACKAGES
Sensor Packages are add-ons to normal default sensors. These usually cost tonnage and credits to put into your ship. Some are even illegal to own. To activate an installed package is an action, which may require a roll. Most packages can work with both sensor modes, unless specified in the description. Named sensor packages from specific companies or places are generally better than generics.
Name: | Description | Roll Bonus |
Hyper-Spectral Imager (HSI) | A combined electro-optical/active sensor array that measures the spectral signature of targets of interest against the expected spectral signature of the background area. Useful for detecting camouflaged or otherwise obscured targets. | +1D to searching for hidden targets. Easy Sensor roll to activate. |
Inverse Synthetic Aperture (ISA) | Active sensor systems that create virtual swaths based on the pitch or yaw of the target. Since the size of the aperture is dictated by the motion of the target, ISAS detection capability is not limited by range. Useful in detecting relatively stationary small targets in high-noise environments. | +1D to focus on one target and stay locked, Easy Sensor roll to activate, base difficulty to lock on target is range + any Countermeasures or Evasion Maneuvers used. |
Moving Target Indicator (MTI) | A pulsed sensor signal that detects moving targets by measuring changes in the return signal doppler effect over time. Useless against stationary targets or targets that are moving in parallel to the sensor. | +1D to Sensor roll to find moving targets, but -1D to find non-moving targets. Moderate Sensor roll to activate. |
Phased-Array Sensors (PAS) | Large fields of small active sensor transceivers which allow for wider scanning swaths and more sensitive target detection in high threat, high noise environments. | Full +2D to gain, always on, active sensors only |
Suicide Switch | Device used by smaller ships in a battlegroup to masquerade as a high value asset, usually a Heavy Cruiser. The suicide switch mimics the sensor cross-section of the high-value asset, making the user a more attractive target for incoming offensive missiles. | Sensor Roll+4D vs. enemy sensor rolls to make them think you are something else |
Crystal Gravfield Traps (CGT) | An extremely rare and expensive type of sensor that used a synthetic crystal grid to detect and identify fluctuations in the local gravity field. They could be blocked by the presence of mass, not being able to detect a ship on the far side of a planet due to its mass.
| Activation=Moderate Sensor roll Cloaked ships within range are revealed Active and Passive modes
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Dedicated energy receptors (DER) | A passive sensory device capable of detecting electromagnetic emissions in its surroundings. Using it, a skilled operator would be able to detect emissions from lasers, beacons and comlink transmissions. Can usually be used in large arrays to find weaknesses in Planetary Shields.
| Activation=Easy Sensor Roll +2D to detect EM Emissions Passive only
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Electro photo receptors (EPR) | The simplest kind of sensor. It integrates information from normal light, ultraviolet, and infrared telescopes to create a composite hologram or two-dimensional image. An EPR is useful only at comparatively short ranges, but is relatively inexpensive, and often sees use as a targeting sensor.
| Activation=Very Easy +1D to Passive sensor checks +2 to Active sensor checks
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Full-Spectrum Transceivers (FST) | Uses a variety of scanners to detect an incredibly diverse array of phenomena. However, its versatility is limited by its low sensitivity and by the large size of the rectenna dish required to detect accurately or over large distances. Most non-combat starships were equipped with FSTs. | Activation=Very Easy +1D to Passive sensor checks +2 to Active sensor checks
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Hyperwave Signal Interceptors (HSI) | A sensor that detected the telltale fluctuations in the local hyperspace field that resulted whenever a starship entered or exited hyperspace. They cannot indicate the origin or destination of a ship, but can record its entry or departure, as well as its mass and speed. HSIs can also be used to tap into hyperradio transmissions, like those sent by subspace radio or on the HoloNet.
| Activation=Moderate +2D to sensor checks to detect ships + ect +1D to Communication checks
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Life Form Indicators (LFI) | Though typically grouped with sensors, is technically a sophisticated computer program designed to be used in conjunction with other sensor types. They analyze the data provided by other sensors to determine if a life form is present, and if so, what kind. For example, a full-spectrum transceiver might detect a 37.0 Celsius mobile heat source, massing at eighty kilograms, and that the ship's life support systems are provding a standard terrestrial atmosphere and gravity; an LFI would conclude that this being is probably a Human.
| Activation=Easy +2D to sensor checks to Detect Life and Species ID Active and Passive |
Towed Sensor Array (TSA) | The TSA improves the passive reception by the use of a trailing antenna deployed after the ship. It is vulnerable to violent maneuvering and high speed which tends to snap the antenna. This limits its use to a max safe space speed of 4 and no heavy maneuvers. | Activation=Easy +4D to Passive sensor checks Extends range of Passive sensors, usually double the range |
Some common Packages on most starships are FST and EPR.
Counter Measures
Counter Measures are techniques used by ships in order to avoid being spotted, including sensor jamming, chaff and other distractions. In game terms, when performing different counter measures, it becomes a Sensors Skill+Gain+Package Bonus vs. Sensors Skill+Resistance +Countermeasure Bonus. Of course the enemy can counter with Counter Counter Measures or CCM.
List of Counter Measures
Name | Description | Bonus |
Frequency Switching | An example of CCM -- to switch the frequency of the sensor (active or passive). Of course, nothing prevents the jammer from switching frequencies along with its opponent, and in fact jammers and sensors may switch frequencies thousands of times a second in their continuing cat and mouse games. | +1D to Resistance, Moderate Sensor Roll |
Jamming | The all-encompassing term for active countermeasures that use an emitter to put out a lot of electronic noise aimed at foiling enemy sensors. | Sensor roll + Gain vs. Target Resistance. Easy Sensor roll to activate. |
Reduce the Gain | A CCM used against jamming. A ship reducing the gain on its sensors is equivalent to wearing sunglasses. When a ship does this it can easily see the jamming device, although it still can't easily see the other ships in the area. | +1D to target jamming device, -1D to target anything else. Easy Sensor roll. |
Running Silent | A ship may attempt to confound the sensors of an opponent by running silent, or shutting down all systems except a minimal life support. The ship will drift until power is restored (but since there's no friction in space, it will travel at the same velocity it was traveling at when the systems were shut down). Shutting down power may be attempted in 2 rounds with a Moderate Pilot roll. Restarting engines takes at least one minute. Ships can rarely provide life support for more than 5 minutes while running silent, unless they have been specially modified. | +2D to Countermeasure rolls, to hide the ship. |
Communications Jammer (CJ) | A Communications Jammer increases the difficulty of finding specific frequencies and makes it harder to communicate with ships in the jammed area. This applies to both friendly and hostile forces. Tight Beam Communications Rigs (TBR's) cannot be jammed by a Communications Jammer. | Activation=Very Easy +2D to Comms roll to jam |
Optical Shield ( OSH ) | An optical shield distorts the visual image of the starship when travelling through atmosphere. The ship appears as a dis-coloration or shimmering patch in the sky, which makes it easily confused with natural phenomenon. This type of shield does not protect against weapons or sensors, only against the naked eye. | Activation=Easy Die Value vs. Perception rolls
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Cloaking Device (CLK) | The ultimate sensor countermeasure is the cloaking device. It 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, merely a patch of empty space. The main tactical drawback is that a cloaked ship is electronically blind since no sensor or communication systems can work inside a cloaking field, only visual systems can function properly. A cloaking device must be custom-built for each ship and are also hideously expensive to build and maintain. Possession of a cloaking device is a Class One infraction under Imperial Law, punishable by death. | Activation=Moderate Ship invisible to all sensors, visually, and it's own sensors.
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False Target Generator (FTG) | A countermeasure against active sensors generates a false target to the enemy sensors, which appears to be a duplicate of the real ship being targeted. Many false targets can be generated. In the future this may become an extremely effective countermeasure, but for now the false targets have difficulty fooling a well-trained operator. | +1D to Sensor roll to generate a false target, Moderate Difficulty to put the false target where the operator wants it to be. |
TERMS TO KNOW
What follows are some terms that might help or fill in some color for your character.
COUNTERMEASURES (CM): Steps taken by ships in order to avoid being spotted, including sensor jamming, chaff and other distractions.
COUNTER-COUNTERMEASURE (CCM): Used by a ship's sensors to counter the effects of enemy countermeasures (see countermeasures).
LATENCY (AKA "time delay"): Latency is a measure of the lag-time between transmission and receipt of data. Partially a function of distance at long range, also driven by processing speed, bandwidth availability, message priority and transmission power. (Rule of thumb-beyond 24 Space Units latency becomes an issue.)
SENSOR CROSS-SECTION: The apparent size and geometry of a target on a sensor scope.
(Moderate Sensor roll + range mods vs. any countermeasures.)
SENSOR SWATH: The area of space covered by an active or passive sensor system.
(Most active sensors have a range of 24 Space Units in diameter. Passive sensors have a range of 1-4 Space Units)
SYNTHETIC APERTURE: A virtual sensor aperture that is created by the motion of the sensor platform through space. As the platform changes position, the sensor system builds detailed imagery over a wider scanning area. Highly effective for charting the location and composition of stationary targets. (Gives a +1D to Sensors rolls for every round spent charting the location. -1D to sensor operator's other actions while performing this ongoing active scan.
Example: The Imperial Scout Ship, detecting Marka's ship from the Active scans emitting from it, attempt to hide in the ionosphere of a planet. While at the same time, they begin jamming Marka's sensors. Marka, upon losing the ship from her scopes, attempts to filter out the jammers, by rolling her resistance dice, she gets a 5, but that's not good enough. She then reduces the gain on her sensors, thereby finding the jammer, sends the co-ordinates to the weapons officer, and then proceeds to send out recon fighters to do active scanning, while turning off the ship's active sensors. The Imperial scout ship, detecting missiles incoming send out their fighters or missile defense fire. Meanwhile, Marka has sent out her recon fighters and using their active sensors to gets a cross-section of the enemy ship, they find a critical target location. Marka then sends the data to the weapons officer for targeting. And so on, until the enemy ship is taken out or disabled.
Limitations on Sensors
Sensors must be used by a skilled operator in order to be effective. Furthermore, sensors are line-of-sight, meaning a target hoping to avoid detection may attempt to hide behind another ship, planet, or other sensor-blocking phenomena. A ship could also use any of the techniques described above in the previous section. Sensors are also limited to the EM spectrum and the laws of physics.