Narrowband EMDAR

Narrowband EMDAR uses the same passive EM detection system as broadband EMDAR but is far more directional. To achieve this, narrowband EMDAR can only focus on a very limited area of the TOE grid.

The narrow focus limits the amount of detection data that needs to be processed, so that multiple processing cycles can be completed in the same time it takes a single processing cycle for the vast amount of data generated by broadband arrays. This means a narrowband array can calculate movement and adjust its focus accordingly, allowing it to track a moving EM source such as a TSMO.

Achieving a Track

The successful detection of a TSMO by a narrowband array is referred to as a ‘track’.

Before a narrowband array can begin tracking a TSMO, it’s narrow area of focus means that it must be directed to the area of space within +/-100GU’s of the TSMO’s location. The contact management process allows operators to continually refine their estimate of a TSMO’s location until a narrowband array can achieve a track.

Maintaining a Track

Narrowband arrays are significantly more sensitive than broadband arrays, allowing them to track EM sources which might not otherwise attract attention on a waterfall display.

In additional to EM detection the narrowband system utilises computational analysis which extrapolates the tracked TSMO’s position based on speed and heading, even where no detectable EM is being emitted. The system will follow this virtual track until new EM is detected, as when the TSMO changes heading or speed.

Equipment Limitations

Narrowband arrays are positioned around the vessel in redundant, overlapping sets. The directional nature of narrowband requires line-of-sight to the target. An array will automatically hand off tracking to another when a target moves out of range.

While there are a significant number of physical narrowband arrays installed, the need to keep arrays spare at each location for tracking handoff and the significant computational resources required by the system means that only six virtual arrays are presented to operators for use. This limits the maximum number of tracks that can be maintained, but is thought to be adequate for most tactical scenarios.