Sensors

Sensors, often called scanners, refer to the various kinds of detection technologies used by starships and installations. Although the term 'sensor' can refer to an extremely large number of detection devices, the term has, in the popular lexicon, almost exclusively refers to technologies used for detecting starships. A variety of types of sensor are used throughout the galaxy, ranging from simple radar arrays to complex tachyon beam emitters.

There are two types of sensors: passive and active. Passive sensors exclusively gather data that hits them, such as electromagnetic waves and infrared signatures. Active sensors emit energy which is reflected off of objects and measured in return. Both of these have their own advantages: passive sensors are stealthy and require little power, while active sensors can detect objects that are not emitting energy. As such, both sensors are used together: passive sensors are always enabled, while active sensors are enabled when necessary.

Most starships are equipped with a number of different sensors, with the detection results collated by the ship's computer for simple display and understanding. As the vastness of space provides virtually no cover, a single ship can detect everything in a star system that is not hidden by a celestial body. Ships can hide from sensors by moving behind something, such as a planet or asteroid, or by engaging a cloaking device. Some ships may choose to hide in plain sight, by disguising themselves as civilian ships, space debris, or asteroids.

Infrared

Infrared sensors, sometimes called thermal sensors, are used to detect the heat output of objects. As space lacks a medium to contain heat, any objects generating heat, such as a spacecraft or station, are extremely easy to detect. Exhaust plumes and ship reactors run extremely hot and are easily detectable from significant distances. Although heat emissions can be lessened via the use of heat sinks and drifting on inertia, these methods are short-lived.

Radar

Radar functions by detecting electromagnetic emissions, namely radio waves. Active radar emits periodic radio pulses which are reflected off of nearby objects and picked up by the emitter. Passive radar instead 'listens' for radio signals from other radars to determine their location. Radar is extremely common in space travel, primarily for navigational purposes, but also for medium-range shipfinding. Due to the speed of light, the usefulness of radar at extreme distance is limited.

Lidar

Lidar, also called laser scanning, utilises laser beams to find the distance to a point. A brief laser pulse is emitted, and the lidar system measure the exact amount of time the laser took to bounce off the object it hit and return. This allows for extremely accurate and detailed surface mapping, making lidar the main tool of planetary cartographers. On starships, it is used as both a long-range distance finder and a short-range navigation assistance tool, alerting pilots to objects in close proximity.

Gravitic

Gravitic sensors scan for fluctuations in gravity waves, measure them, and calculate the distance and mass of the object created them. As all physical objects have mass, they create gravity waves that can be detected by sufficiently sensitive scanners - the smaller the object, the harder it is to detect. However, collisions of objects and other changes in mass can create large gravity waves that can overwhelm gravitic sensors, making them unreliable in chaotic conditions.

Subspace

Specialised sensors can reach into the dimension of subspace and use it to track ships at extreme distance. Movements in realspace create waves in subspace that travel at effective speeds significantly faster than light. This allows for ships to be detected well beyond the light horizon, such as in neighbouring star systems dozens of lightyears away. This effect is magnified for ships travelling through hyperspace, as they emit extremely strong subspace waves. Although this technology has been in use since the dawn of faster-than-light travel, it wasn't until the late 23rd century CE that it could be miniaturised sufficiently for use on general starships.

Tachyon

Tachyons are particles that naturally travel faster-than-light. An emitter projects a beam of tachyons at a point in space, which nearly-instantly travel to the target and reflect back to the source. Like lidar, a sensor calculates the amount of time it took for the tachyons to travel the round trip, thus determining the distance to the object. This can happen multiple times per second, with the changes in an object's distance determining its relative speed. Tachyon sensors have been suggested as replacing lidar, but the extreme cost in both resources and energy to create and power a tachyon sensor mean they are still relatively uncommon.

Biosign

Biosign scanners, also called life sign scanners, use a variety of sensor types to determine the presence of life in a given area. These can include electromagnetic sensors to detect faint bioelectric signatures, chemical sensors to detect emissions like hair folicles or exhaled carbon dioxide, ultrasonic scans to detect motion, and thermal scans to detect heat signatures - among others. Although not perfect (especially so when done from space, where most of the sensors do not work), biosign scanners can quickly determine whether there are biological entites in an area, their species, and their approximate number.