• Threat warning or detection and identification of hostile weapons systems (i.e. radar warning receivers, passive sonar)
• Surveillance and detection or the tracking and identification of all targets and events within a general area.
• Fire control or acquiring, tracking, and engaging targets using a fire control sensor (i.e. radar) to director weapon delivery. These sensors can be either passive, active, or combine both modes to provide for one of the functions listed.

Today, Knowlege based systems are being experimented with to help make the kinds of decisions only a human operator can make, and to combine the comuter's ability to manipulate larger amounts of data while applying the human decision process to sensor supplied data. The technology is being explored as part of the Army/Air Force Joint Tactical Fusion Program. One element of this program is the All Source Analysis System (ASAS), a transportable semiautomatic tactical intelligence data processing system known as the Enemy Situation Correlation Element (ENSCE). The objective is to combine data from a large variety of sensors to provide verified data about the conditions in the battlefield. There are a number of discrete sensor characteristics that must be considered in evaluating sensor systems:

Detection Performance

Detection characteristics (false alarm rate, detection probabilities and ranges) for a calibrated target characteristic in a given noise background.

Spatial/Temporal Resolution

Ability to distinquish between two or more targets in space or time.

Spatial Coverage

Spatial volume covered by the sensor, for scanning sensors this may be described by the instantaneous field-view, the scan pattern volume and the total field-of- regard achievable by moving the scan pattern.

Detection/Tracking Modes

Search and tracking modes performed: 1. Staring or scanning 2. Single or mulitple target tracking 3. Single or multimode (track-while-scan/stare)

Target Revist Rate

Rate at which a given target is revisted by the sensor to perform sample measurement (for instance, staring sensors are rated as continous).

Measurement Accuracy

Accuracy of sensor measurements in terms of statistics.

Measurement Dimensionality

Number of measurement variables (range, range rate, and spectral features) between target categories.

Hard/Soft Data Reporting

Sensor outputs are provided either as hard-decision (threshold) reports or as preprocessed reports with quantitative measures of evidence for possible decision hypothesis.

Detection/Track Reporting

Sensor reports each individual target detection or maintains a time-sequence representation (track) of the target's behavior.