The human eye can discern spacecraft only out to a few kilometers. Beyond that distance the spacecraft is lost in the void of space. Space, however, is infinitely huge and does not accommodate to human abilities. Therefore, a starship’s sensors augment and enhance the crew’s own abilities, allowing them to detect and see starships much farther than normal.

A spacecraft’s sensors use a combination of passive visual and EM sensors as well as active ladar and radar emitters to provide the pilot with an accurate picture of the space surrounding the craft. More sophisticated sensors even employ advanced Gravimetric sensors to detect the mass of a remote starship and Hyperspace Wave Distortion sensors to detect active Hyperdrive use or Hypercomm transmissions. Civilian spacecraft rely on accurate sensor readings to navigate and maneuver while military spacecraft use even more accurate sensors to acquire and track threat spacecraft as well as coordinate the activity of allied or subordinate craft. Under normal operations, all spacecraft navigate and maneuver using active sensors. Active sensors provide detailed and accurate information but are easily detected by other spacecraft. Under certain circumstances a spacecraft may operate under passive sensors only. Passive sensor operation provides less accurate or detailed information than active sensor operation since it can only detect emitted or reflected ambient EM radiation but has the advantage of making the vessel itself harder to detect.

Each spacecraft equipped with sensors lists the sensors Detection Range and Identification Range. The Detection Range is the distance at which point the spacecraft will become aware of the existence of an object or energy source. At this point, the information provided by the sensors is too limited to provide an accurate identification of the remote object. All that is known is the object’s size or mass, it’s heading, and what kind of energy it might be generating or transmitting. The Identification Range is the distance at which the sensors provide enough information for an accurate identification of the object. At this range, sensor operators, or computer databanks, can determine the identity and intention of the craft or object. Identification Range is considered the maximum range at which a spacecraft’s weapons can target and open fire on an opponent.

A spacecraft operating with passive sensors only, or "running silent", can detect other craft if the other craft is using active sensors at a range equal to the other craft’s Active range.

A spacecraft’s sensors can detect other craft using more powerful active sensors at the other craft’s active-range.

Spacecraft equipped with advanced sensor suites may attempt a Scan against a single target. A successful System Operation skill test provides more detailed information about that target, including life signs, power output, material construction, etc.

Human eye, Level 0

Strider, Level 1

Grav Flier, Level 2

Starfighter, Level 3

Corvette, Level 4

Starship, Level 5

Exploration Starship, Level 7

Starbase, Level 9

Observatory, Level 10

At the range listed, a starship can detect a human-sized object. Each increase in the size of the object increases the effective range at which that sensor can detect that object. For example, a starfighter can detect a human-sized object at 3000 kilometers but can detect another starfighter out to 300,000 kilometers or a starship out to 3 million kilometers. The starfighter can only identify a human-sized object within 30 kilometers or can identify a specific starfighter out to 3000 kilometers. 

A starship’s sensors, on the other hand, can detect a human-sized object out to 300,000 kilometers, the equivalent distance of the Moon from the Earth. It can detect the presence of another starship out to 30 billion kilometers, roughly the same distance of Pluto from the Sun, though it couldn’t identify the starship from any other starship until it was within 300 million kilometers, roughly the distance of Mars from the Sun. It can detect the presence of any Jupiter-sized planets out to 30 trillion kilometers (approximately 3 light years or 1 parsec).