Any vessel with a control room has a basic comm/sensor array. Some vessels have enhanced, multipurpose, science, or tactical comm/sensor arrays. All are integrated communication and sensor suites whose capabilities are simplified into a single comm/sensor array level. 

Unless given the FTL option, detection and communications
occur at the speed of light, and over long distances. Time lag is one second per 186,000 miles, or 500 seconds per AU, each way.

Arrays have the following navigational, sensor, and communications capabilities:

  

Passive Sensors

Comm/sensor arrays include telescopes (visual, infrared, ultraviolet, radio) for navigation, detection, and targeting.  They usually operate in infrared mode for long range detection, but also produce telescopic imagery (“on screen”) or perform multispectral sensing.

Passive sensors are operated from a control station (or by a sapient program). The operator uses Electronics Operation (Sensors) skill, using the Sensors rules (p. B471). The sensors are vehicular imaging sensors (p. B471) that provide Hyperspectral Vision (p. B60) with Extended Low Band (and Extended High Band, for science and multipurpose arrays), Telescopic Vision (p. B92) and 360° Vision (p. B34). The Telescopic Vision Level is equal to the comm/sensor array level.

Passive sensors can also detect and locate any operating active sensor or broadcast signal within twice its own range (see Signal Detection, below).

Spacecraft will usually be using passive sensors to detect other spacecraft. The relevant modifiers are summarized below. Roll vs. Electronics Operations (Sensor) skill adding the modifiers shown below; if the modifiers total +10 or more, the GM may assume automatic identification. Passive sensors only detect objects in line of sight – something behind a world, larger station, underwater, etc. won’t be detected.

Modifiers:

SM: Add the object or spacecraft’s Size Modifier.

Time Spent: Assume a complete scan around the vessel takes 20 seconds. Time spent modifiers apply (e.g., +3 for a full 3-minute space combat turn, or +5 for half an hour).

Range: Apply the Range modifiers from p. B550. In space combat, -10 at zero (100 yards), -30 at point-blank (100 miles), -34 at close (500 miles), -38 at short (2,500 miles), -42 at long (10,000 miles), -46 at extreme (50,000 miles). For astronomical ranges: -50 at 200,000 miles (1 LS), -54 at 1 million miles (5 LS), -60 at 10 million miles (100 LS), -66 at 100 million miles (1 AU), -72 at 1 billion miles (10 AU), -75 at 7 billion miles (75 AU; scan entire solar system).

Telescopic Vision: Reduce the above range penalty by the level of Telescopic Vision. You may “zoom in” and use twice the Level if the target’s approximate location is already known. This includes attempts to get a better look at a detected target, rolls to spot targets whose orbits are already charted (e.g., charted satellites, celestial bodies, etc.) or whose radio, radar, or transponder emissions have been detected.

Damage: If an enhanced, tactical, multipurpose, or science array is disabled or destroyed, a vessel can use its basic array.  A basic array is only destroyed if the control room or spacecraft is destroyed. All arrays are at -1 if the spacecraft is reduced to 0 HP or less.

Observation: +10 if object is in plain sight (in space, air, or a world’s surface) rather than concealed, camouflaged, hidden among debris, or using a Cloaking Device.

In Space: +2 if the object is silhouetted against a larger celestial body, +24 if silhouetted against deep space. Note that this is cumulative with the plain sight modifier.

IR Signature: Spacecraft often put out a lot of heat and light! If trying to detect a spacecraft or similar object, apply the single highest applicable modifier:

Minimal power: 0*.

Auxiliary power: +3.

Fuel cell, solar panels, or jet engine: +4

MHD turbine, chemical or HEDM rocket engine, or flying in atmosphere at 3,600+ mph: +5

Fission reactor, nuclear thermal rocket, nuclear light bulb, or performing a high-speed atmospheric reentry: +6.

Antimatter thermal rocket engine, antimatter reactor, fusion reactor, super fusion reactor, total conversion reactor, magsail, lightsail: +7.

Fusion pulse drive or fusion rocket engine: +8.

Advanced fusion pulse, antimatter plasma, nuclear saltwater rocket, or external pulsed plasma engine: +9.

Antimatter plasma torch, antimatter pion, or fusion torch engine: +10.

Antimatter pion torch, super antimatter plasma torch, or total conversion torch engine: +11.

Super conversion torch engine, or any “cosmic” power plant: +12.

Reaction engine modifiers assume the rear hull (with drive) is facing toward the sensor array; if it’s the central hull, reduce by one; if it’s the front hull, reduce by two.

Countermeasures: The following modifiers apply:

-10 if target is using a cloaking device.

-2 x (TL-4) if using a stealth hull unless the target has signature modifiers of +5 or more.

* Auxiliary power permits operation of all non-high-energy or cosmic energy systems. Minimal power does not permit the use of any life support (except hibernation chambers), active sensors, or ECM.

Failure means no contact (a critical failure may mean a misidentified contact or other error); the operator may repeat the task on later turns if there is reason to believe something is out there.

Success means detection of the object’s presence, range, course, temperature class, and SM, but no other details. Once an object is detected the sensors will automatically keep track of it (along with anything it launches). It remains detected as long as it remains in line of sight and does not activate a cloaking device. If it cloaks, a new detection roll is required. If it leaves line of sight and reappears later, a new roll is also needed.

  

Signal Detection

The passive sensors in comm/sensor arrays also incorporate radio, laser, and radar detectors. If a vessel is using radar or broadcasting radio signals, or using a transponder, these
sensors automatically detect the signal out to twice the active or broadcast range. (1.5 x range if the signal was low probability intercept (LPI) – see p. B82). Ladar and tight beam laser comm signals are detected only if the spacecraft was their target, or happened to be in their path. FTL radio and pararadar multiscanner emissions can only be detected if the vessel also uses such a system; if so, treat them as radio and radar, respectively. The sensor operator will detect the type of signal, the content of any (non-encrypted) broadcast and an approximate bearing (passive sensors can use twice their Telescopic Vision level from range modifier). A successful Electronics Operation (EW) roll can also reveal useful details (“that was a Type 23 radar used by the Federal Navy”).

  
Active Sensors

Active sensors in a comm/sensor array consist of radar and ladar used for navigation, detection, and targeting. Their range is measured in light seconds (one light second is 186,000 miles). They can be operated from one of the vessel’s control stations or its computer. All sensors can generate multiple sensor beams that can track any number of targets simultaneously.

Active sensors are less important for spacecraft than passive sensors; usually the passive sensors detect targets at much longer distances. Active sensors are mainly used as part of targeting systems, for radar mapping of worlds (especially if cloud covered) and, in the case of superscience multiscanners, for “sensor scans” to analyze a target. Active sensor use in space combat is integrated into the combat rules in Chapter 4. Otherwise, use the vehicular active sensor rules (p. B471-472).

All types of array can be used as a radar (p. B81) with the Extended Arc (360 degrees), LPI, and Multimode enhancements. Enhanced, tactical, and science arrays also include a
ladar with (p. B81) with Extended Arc (360 degrees) and LPI enhancements; see Scanning Sense, pp. B81-82. If the spacecraft has the multiscanner design switch all arrays have a para-radar (p. B81) with the Extended Arc (360 degrees) enhancements.

The active sensor’s range in light seconds is determined by the array level: see Active Sensor and Comm Range Table below. You can multiply by 200,000 to get range in miles. On a world, it can see out to the horizon.

  

E.g., a Level 8 array has a 1.5 LS range active sensor and 1.5 AU range comm suite.

  

Communications (“Comm Suites”)

Comm/sensor arrays have very long range laser communication and radio (p. B91), communicators. Range depends on the array level – see the Active Sensor and Comm Range Table, reading the range in astronomical units (AU). Use the communications rules on p. B471 and p. B91. Spacecraft also have internal intercoms in all systems except armor and fuel tanks, as well as outside next to airlock, hangar, and cargo doors.

  

Transponders

Comm suites may be set to automatically broadcast identification codes for traffic control purposes. Regulations may require civilian spacecraft to broadcast their identity using
transponders whenever they are operating in civilized shipping lanes. Crews that find this onerous may reprogram them to emit false identity signals. Reprogramming a transponder may be a trivial exercise, or it may require difficult Electronics Operation (EW) or Computer Programming rolls (GM’s discretion). The usual deterrent to using a false signal or no signal is fines or worse if caught by authorities.

  

  

Dominion Space Rules

Standard Assumptions

Being GURPS, the above rules have to apply to everything, within Dominion Space, tech level and common technology permit the following simplifications:.

• A Basic Sensor array has the same level as the ship’s size modifier (SM)
  • Enhanced arrays add +2
• Space combat turns will usually be Standard length, so +3 if using the full turn
• For detection purposes, the standard Hyper Mass Thruster engine has a waste heat signature that gives a +10 modifier to detection rolls

  

Special Rules

• Jumping into or out from hyperspace creates an EM blip equivalent to using an Active Sensor of the ship’s size
  • A stealth hull reduces this by 2 SMs
  • A successful engineering check can further reduce the signature on a case-by-case basis, however, the Navigator must allow for it (increasing the difficulty of plotting the jump) or there is an increased risk of jump error if they have not
• The rule ‘-2 x (TL-4) if using a stealth hull unless the target has signature modifiers of +5 or more.’ effectively makes stealth hulls useless as almost every ship in the Dominion has a signature modifier of +5 or more, so I rule that the stealth hull bonus always applies to reduce the signature.