Starship Sensors

See also: Stealth.

A vehicle has a Perception stat which is a general measure of how extensive its sensor systems are. Vehicles only have a Perception rating if they actually have something like radar, rather than relying on Mk I eyeball to spot things.

See Example Starships for some starship sizes, which will give an idea of how easy some things are to spot.

Based on the Perception, which is a factor of the design, and the skill, which is a factor of the computer systems doing the processing. Standard software is determined as follows:

Quality software is +1, expensive +2, cutting edge +3. May be modified by a good operator.

How easy it is to spot things depends on the type of sensors you have, and how exhaustive they are. Sensor types are as follows

Multiple turret sensors on the same craft can be combined. Increase range by the square root of the number of turrets - if mixing sizes, a heavy turret counts as 2 light, a barbette as 3 light. Bay sensor suites can't easily combine.

Deployed arrays can be combined, multiply range by number of arrays.

Modify PER according to the following options:

A basic sensor effectively takes up no volume in a spacecraft, and are fitted as standard in most designs. They are robust, reliable and lightweight, however they are really designed as backup in systems which already have extensive sensor coverage from fixed systems.

A Dedicated Sensor takes up 1t of dedicated space, and is normally turret mounted.

To detect something, the basic difficulty is 0. Add +5 for each range band of distance, and -5 for each point of signature (normally just Size) of the object being detected. No roll is made, if the Perception x Skill of the sensor beats the difficulty, then it is automatically detected.

For example, a typical TL10 Traveller ship may have a Perception of 3, and a software rating of 6 (it's software has been upgraded recently). This gives a total of 18, with a range band of 3”. It could detect a small fighter (Size 14) at a range of 51”. If it had a light sensor turret, with a rating of 24, range 10”, then the same fighter would be detected at 180”.

A Broadsword class mercenary cruiser (800t, Size 25) can be detected out to 290” in the latter case.

A Class A starport will often have a dense orbital array, rating (9×8) 72, range 1,000,000”. It would detect the fighter out to 28,000,000km. If it was using thrusters, then this increases to 280,000,000km (almost 2 AU), or 20 AU to know that something fighter-like was there.

A small private base on a moon probably has a deployed array, rating 48 range 1,000km. It's extreme edge is 240,000km, or 2.4MKm for anything using thrusters.

The detection range is actually the range at which the target will be identified. Out to double the range, it is possible to get a fix on the target (not good enough for shooting with anything other than missiles) and an estimate of its mass (to 2 significant figures). Out to ten times the range, a very rough order of magnitude estimate can be gleaned, with its rough location and mass (nearest order of magnitude).

Note that anything broadcasting IFF, will be picked up and identified at this extreme range. A ship that is running silent (shutdown drives and as many other systems as possible) can halve the detection range.

Other modifiers:

A sensor system can switch to passive only, in which case divide detection range by 10.

Planet based sensor system are similar to Orbital, but may be limited by atmosphere. Divide range according to the atmosphere type:

The above all assumes real time indications of something being there. A clever person (or computer system) can pull back data for a larger time window and detect things a lot further out. An analysis of the last hour's data can extend the range by x10, the last 100 hours by x100, the last 10,000 hours (416 days) by x1000.

Military installations will probably do this, Class A starports or those on high alert may as well, but it is rare for anyone else to bother since it requires computer resources and man power.