TRAVELLER Special Supplement 4: Sensors
POST Three - Basic Sensor Package.
The BSP (Basic Sensor Package) is a suite of both active and passive sensors included as basic components of the ship's Bridge assembly when starship/spaceship construction is undertaken. BSPs are available starting at TL 9.
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BSP SENSOR SUITE
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- EMS Active</font>
- EMS Passive</font>
- RADAR</font>
- RADAR direction finder</font>
- Radio direction finder</font>
- LADAR</font>
- MADAR</font>
- Laser Sensors</font>
- HRT</font>
The BSP's effective detection range is about one-half light-second. Bogeys that rig for silent running can be detected at half that range. Bogeys in orbit can be detected at 1/4 that range. Bogeys rigged for silent running and in orbit of a world can only be detected at 1/8 that range. Once a target is detected, though, it can be tracked up to a distance of three light seconds (or its initial detection range, whichever is longer).
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">BSP Grade Close Short Long Extreme
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Standard (km) 100K 150K 300K 600K
(LS) 0.33 0.50 1.00 2.00
Military (km) 300K 600K 900K 1200K
(LS) 1.00 2.00 3.00 4.00</pre>[/QUOTE]Military grade sensors have an effective range of about four times that of standard grade sensors, though military grade sensors are typically restricted and unavailable to those vessels built outside of a military organization. Exceptions do exist, and such is the case with many Scout craft.
Sensor Scans detect other vessels (and objects). A scan provides general information about the object scanned.
The first activity normally conducted after tumbling back into N-Space from a jump is a sensor scan in order to detect nearby objects. Since the vast majority of spacecraft employ constant-signal transponders, becoming alert to nearby vessels is usually instantaneous and immediate.
Sensor Locks provide detailed information about objects detected with sensor scans.
Objects must be detected first from a scan before they can be locked, and sensor locks are required for an enemy vessel to be targeted in space combat.
An
active sensor is one that emits a signal then reads that signal once it returns after bouncing off a detected object. RADAR works this way (as does the flashlight when flashed into a dark room). A
passive sensor is one that simply detects transmissions without emitting any signals of its own. Streetlight sensors work this way (and so does the naked eye).
Passive sensors can be used for both sensor scans and sensor locks, but passives are better suited to scans.
Some active sensors can be used for both sensor scans and sensor locks, but many active sensors are "directional" instead of "broadbeam" and therefore are only capable of sensor locks. Active sensors are better suited to sensor locks than passive sensors, and active sensors typically provide more detail about a detected object than a passive lock will provide.
Passive sensors typically have much greater range than active sensors as active sensors must send a signal out and wait for it to bounce back before the return can be read. (Passive sensors receive incoming signals in half the time.)
Passive sensors that can be used in both sensor scans and sensor locks have the capability of being focused in a narrow tight beam. For example, the Passive EMS sensor will receive incoming data omni-directionally when in scan mode but can also be focused (as a telephoto lens used on a camera) on a narrow target. This latter setting of the sensor is used for passive sensor locks.
Since vessels are typically continually broadcasting transponder information, making the ship an active target to enemies, active sensors are used just as often as passives (Military vessels rely slightly more on passive sensors). The ship's computer functions in collecting data reported by the various sensors and presenting it in a form that is relatively easy to digest by the sensor operator. More powerful computer systems provide faster, better quality results than computers ranked with lower model numbers.
RADAR is an active sensor that detects objects by emitting radio energy across wide angles before detecting that energy when it bounces back from distant objects. Radar can be used for active sensor locks, but is most often used for active sensor scans.
LADAR is a similar active sensor to RADAR, except that it uses a tight beam laser rather than radio energy to bounce light off a target. Sand from sandcasters can make use of a LADAR less effective. And, LADAR can only be used for sensor locks (not sensor scans).
MADAR is a similar active sensor to LADAR, using a microwave signal. It, too, is a tight beam active sensor that can only be used for locks but not scans.
HRT is a High-Resolution Thermal detecting device. It's a passive sensor that detects targets by their emmitted infrared radiation (heat). HRT can be used for either a passive sensor scan or a passive sensor lock.
EMS Active is an advanced version of RADAR which incorporates the use of wavelengths other than radio and includes sophisticated computerized image enhancement of the electro-magnetic spectrum. EMS Active can be used as either an active sensor scan or active sensor lock.
EMS Passive is an advanced (incorporates a camera) passive sensor that has the capabilities of HRT plus EMS direction finders and computerized image enhancement. EMS can be used for either passive sensor scans or passive sensor locks.
EMS Frequency Bands are longwave radio (ex: power line networks), shortwave radio (ex: televison), microwave radio (ex: all-weather RADAR), heat and infra-red (ex: any heat source), visible light (ex: light from stars), ultraviolet light (ex: artificial light), X-rays (ex: emitted from gas giants), and Gamma rays (ex: emitted from nuclear explosions including that in stars). A spectrometer is a piece of an EMS sensor, providing spectral analysis on all wavelengths of light.
Laser Sensors,
RADAR Direction Finders, and
Radio Direction Finders are all passive sensors that can locate and classify energy emissions, indicating size and power level status. These sensors can only be used in passive sensor scans.
Tight Beam sensors, like LADAR, are indeed active sensors. But, because of their tightbeam nature, a vessel may be able to rig for silent running without being considered active and still use tight beam active sensors. The reason for this is their relatively low energy output (nothing when compared to the ship's power plant) and the fact that an enemy vessel has to cross the beam in order to detect it. Note that a ship using tight beam sensors will be considered active by the target ship!
Visual Range is generally considered to be around 10,000 km, but this does not mean an enemy vessel can be spotted from inside a vessel, through a port, at that distance with the naked eye (actual naked eye range is much less). This refers to the HRT and EMS sensors' ability to use a telephoto lens, spectral imaging and computer enhancement to report an actual image of target craft. At any range beyond 10,000 km, the HRT and EMS sensors begin to contruct computer aided "guesses" instead of reporting the target's actual image. Though, with longer amounts of time (more than one space combat round), the EMS sensor's spectrometer function can be used to report actual images from incredible distances.
Passive Sensors can have fantastic range, viewing into other galaxies if tuned properly and given enough time. The ranges described above, for both actives and passives, are provided with space combat in mind. When ship's sensors are used for other purposes, the GM should make a determination on the type of results the sensor reports.
This detail is presented for roleplaying purposes and GM reference only. As presented in the next post, the mechanics of these sensor rules call for a single, simple detection die roll. If successful, a sensor scan is made and all targets scanned are also considered target locked. These rules should also be used without die rolls--the information used as reference whenever sensor data is called for during a game.
For example, the densitometer (discussed later), HRT, and EMS arrays are important to a Navigator when plotting a course through the dangerous electro-magnetic and gravitational jetties of the upper atmosphere of a gas giant when skimming fuel.
The ship's densitometer is relied upon heavily when the Navigator informs the captain that the ship has passed through a planet's 100 diameter gravitational zone. (Vessels equipped with the BSP do not incorporate denistometers and thus must keep track of the 100 diameter limit by range finding.)
When a player asks for range to a target, in effect, that information is being reported by the LADAR. Missiles use the LADAR system as they fly towards their targets.
A lot of color can be added to a game by a GM who has a grasp of what jobs for which these sensors can be used. Yet, the game rules are kept simple, so that the game proceeds at a fast, furious, but fun pace. In short, GMs should use as much of, or as little as, this detail as is needed in their games.
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GAME RULE
A light-second measures 300,000 km.
What the BSP will report: Target presence, position, and velocity. When detection is made using BSPs, GMs should give no information other than bogey presence, position, and trajectory. A GM providing more information than this should look closely at the type of information gleaned from a particular BSP sensor type before providing additional details.
Complications a GM may consider when reporting BSP results: Solar flares or strong planetary magnetic fields make scans difficult to perform with accuracy (allowing vessels to hide in these areas). Any type of overpowering radiation can interfere with scans (nuclear missile explosions, sensor jamming devices). Sandcaster clouds reflect light and may make sensor scans difficult. Dense materials will block X-rays and gamma rays. Active scans will almost certainly give away the position of the sensing ship to the enemy.
A situational DM a GM could spring on his players involves the LADAR having to detect a target through a cloud of sand. In a case like this, the same -3 DM penalty used for the ship's laser weapons would be appropriate for any LADAR based throws.
A maximum of four detection throws can be made by the sensor operator each space combat round. One detection throw is allowed per range category, and if detection is successful, then detection is considered automatic at all shorter ranges.
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