Method for characterizing the density of mode S interrogations and responses and secondary radar implementing such a method

A method for characterizing the density of Mode S interrogations and responses in the environment of at least one operational secondary radar (R1), said environment being defined by the airspace domain covered by said radar (R1), said environment being passed through by Mode S targets, a Mode S target being a target emitting a response to the Mode S interrogations emitted by a secondary radar, comprising:

• a first step wherein said radar (R1):
• detects and locates Mode S targets by way of their synchronous responses to the interrogations emitted by said radar (R1) or their positions transmitted in long ADS-B squitters;
• detects (32) asynchronous responses emitted by the same Mode S targets, and therefore not elicited by said radar (R1);
• for each located target, associates (33) its asynchronous responses with the synchronous responses to said radar (R1) or the positions given by said ADS-B squitters;
• a second step wherein said radar (R1):
• based on said association, determines the response rate of each target by counting the number of synchronous and asynchronous responses received from said target for various given time periods;
• with said environment being divided into elementary space cells, determines the response rate per cell by counting the number of synchronous and asynchronous responses received by each target located in each cell, said rate characterizing the density of Mode S interrogations and responses per cell or per group of cells.