This paper reviews the activities related to the development of Mode S as a surveillance tool and provides an update to conference.

Mode S surveillance sensors went into operational service in the United States in the spring of 1994. They operate solely in a Mode A and C role at present.

ATC engineers and planners are actively considering just how Mode S surveillance data is to be presented to the controller. The likely format is for progressive introduction of surveillance capabilities utilising Mode S. These levels are known, in one example, as:

• Minimum Level Enhancement Surveillance;
• Higher Level Enhanced Surveillance;
• Full Two Way Datalink.

Minimum level provides a surveillance function without using the datalink capability of Mode S to enhance surveillance data, but can provide automatic reporting of ACAS resolution advisories. Full two way, datalink is precisely that, the ability to integrate aircraft flight management system data for ATC surveillance tasks. Higher level enhanced surveillance is the incremental step between the two.

To Conclude

The development of Mode S surveillance systems are beginning to move nearer to operational application issues. This is to be welcomed, as the system can then be tailored to the operational need.