Sensors

Sensors are components that detect the presence of target objects either by detecting energy emitted by the target or by reflecting energy off them and detecting the reflection. Active Sensors detect targets at longer range, and are needed for target acquisition, but may give away your position. Passive EM and Thermal sensors don't give you as much information as actives, but they could allow you to stay undetected.

Every military and commercial ship has intrinsic thermal and EM sensors of strength 1 (not listed as components). Adding sensor components will help ships detect enemy ships, planets, and other objects at a longer range. Sensors data is shared, hence the sensor range of a fleet depends only on the sensor range of the ship with the longest range, it is more useful to fit dedicated surveillance vessel than stack them on each ship.

Sensor efficiency can be improved with research, while ECM jamming and stealth technology can render sensors less useful, and jump shock will render them temporarily blind. You can view the active and passive sensors detection radius of your ships and installations in the System Map window by adjusting the Sensors tab values. If you think a 500-strength contact might be out there somewhere, move the slider to 500 and you'll at what distance your sensors would pick it up.

Active Sensors

An active sensor is a "radar" component, that gather target data by bouncing gravitational pulses off a target and are necessary to open fire on a target. Actives allow a ship or a missile to detect targets equal to or above it's stated resolution size within it's stated range. The tradeoff is that progressively stronger active sensors can themselves be detected by passive EM sensors, which can prove a serious tactical vulnerability.

Actives are designed based on the role intended for that sensor. An area search sensor might be designed with a large resolution to find large enemy ships, while a sensor designed to detect fast attack craft would need a small resolution and Missile detection sensors are usually resolution one, which is the lowest possible. A versatile fleet will employ a multiple sizes/resolution sensors.

Active Sensor target detection capabilities can be increased through background research, while Cloaking technology employed by the enemy will making it harder for active sensors to detect. Active sensors also gain tactical intelligence

Passive Sensors

A Passive sensors emit no energy, instead gather target data about their surroundings environment by detecting and analysing incoming emissions. Thermal detect engines, while EM detects active sensors and shields. Both will detect Colonies, where higher EM to thermal ratio seem to indicate the presence of larger population and advanced installations.

When designing passive sensors bigger is better, but it uses valuable space and minerals.

Thermal Sensors

A Thermal sensor is a passive sensor sensitive to infrared radiation, and can detect Ship/missile engines or colony activity thermal signature. The stronger the signature, the farther it can be detected. Engines designed with thermal reduction technology or travelling at less than full speed will emit less heat, and will be harder for Thermal sensors to detect. You can set the speed in the Task Group window.

A few more or less typical thermal signatures, early-mid-game tech:

 Size 4 Missile                  8
 1,000-ton gunboat              88 (no thermal reduction, thus equal to engine power)
 38,000-ton freighter         1350 (they use a lot of big engines)   
 4,000-ton frigate             123 (would have 352 without thermal reduction tech)
 6,200-ton alien cruiser       640 (probably not thermally shielded)
 Mars colony, pop. 67m       7,600
 Earth, pop. 1.5 billion    22,500

A strength-28 (sensitivity 14, size 2) Thermal Sensor, small enough to fit on most ships, would detect them at:

 Size 4 Missile            224,000 km  
 1,000-ton gunboat            2.2m km  
 38,000-ton freighter        37.8m km   
 4,000-ton frigate            3.4m km
 6,200-ton alien cruiser     17.9m km
 Mars colony, pop. 67m      212.8m km
 Earth, pop. 1.5 billion    630.0m km

Not ideal, but at least a ship equipped isn't completely blind. And if you doubled the size, you'd double the range. If you equipped a ship with a thermal sensor 10 times that size (size 20, or 1,000 tons), it would spot the cruiser at 179m km, which is pretty sweet. Just remember that it wouldn't tell what the contact is, just how hot it is. And you can't fire at thermal contacts, unless you play around with missiles that have active sensors, but that's a different matter.

And the size-20 sensor would detect the Earth or Mars colonies from anywhere in the solar system.

EM Sensors

An EM Sensor is a passive sensor that detects EM signatures. These can detect activated active sensors and shield emissions from other ships, or the presence of colonies on a planet. The stronger the emissions, the farther it can be detected. Note that many ships will not emit any EM at all, unless they switch on their actives.

Also note that Earth, in the above example game, has an EM signature of 95,000. That means EM sensors are particularly useful for finding enemy colonies.

Note

• There also Geological and Gravitational Survey sensors.
• Sensor calculation can be taxing on your system, see Game Slowdown for info on related settings.