A LIDAR system adapted for performing airspeed measurements, comprising: - a laser emission source, capable of producing a laser beam towards a portion of atmosphere outside the LIDAR system, so that said laser beam is convergent at an outlet pupil of the laser emission source, and has a transverse beam section which is minimum at mid-length of a focusing zone of said laser beam, wherein said focusing zone has a length equal to 2·λ/(π·θ 2), measured parallel to a center propagation direction (A-A) of the laser beam, wherein λ is a wavelength of the laser beam and θ is a divergence half-angle of said laser beam beyond the focusing zone on a side opposite the laser emission source, expressed in radians, where λ/(π·θ 2) is called Rayleigh length (l R); - a heterodyne detection assembly, arranged for receiving a part of the laser beam which is backscattered by particles contained in the focusing zone; and - a Doppler calculation module, adapted for deducing a speed value for the particles from a beat signal which is produced by the heterodyne detection assembly, characterized in that the LIDAR system further comprises: - a time-control device for the laser beam, which is adapted for putting said laser beam in successive laser pulse form, and which is combined with the laser emission source so that the laser pulses pass through the focusing zone, with a portion of each laser pulse backscattered by the particles, wherein the time-control device is furthermore adapted so that each laser pulse has an individual duration which is greater than or equal to twice the Rayleigh length (l R) divided by a propagation speed of the laser pulses in the atmosphere, and less than 20 μs. - a laser emission source, capable of producing a laser beam towards a portion of atmosphere outside the LIDAR system, so that said laser beam is convergent at an outlet pupil of the laser emission source, and has a transverse beam section which is minimum at mid-length of a focusing zone of said laser beam, wherein said focusing zone has a length equal to 2·λ/(π·θ 2), measured parallel to a center propagation direction (A-A) of the laser beam, wherein λ is a wavelength of the laser beam and θ is a divergence half-angle of said laser beam beyond the focusing zone on a side opposite the laser emission source, expressed in radians, where λ/(π·θ 2) is called Rayleigh length (l R); - a heterodyne detection assembly, arranged for receiving a part of the laser beam which is backscattered by particles contained in the focusing zone; and - a Doppler calculation module, adapted for deducing a speed value for the particles from a beat signal which is produced by the heterodyne detection assembly, - a time-control device for the laser beam, which is adapted for putting said laser beam in successive laser pulse form, and which is combined with the laser emission source so that the laser pulses pass through the focusing zone, with a portion of each laser pulse backscattered by the particles, wherein the time-control device is furthermore adapted so that each laser pulse has an individual duration which is greater than or equal to twice the Rayleigh length (l R) divided by a propagation speed of the laser pulses in the atmosphere, and less than 20 μs.