A STUDY OF AN OPTICAL TECHNIQUE FOR THE MEASUREMENT OF AIRSPEED.

Abstract

A study was conducted to determine the feasibility of obtaining the airspeed of a helicopter by measuring the doppler shift in the envelope of an amplitude-modulated optical beam which is radiated axially and then backscattered by atmospheric aerosol. An optical technique is proposed whereby near returns are not accepted in order to avoid error due to local prop turbulence. It is determined that the signal is spectrally broadened by the random motion of the aerosol and by the short transit time of particles through the bounded air volume being probed. As a consequence long integration time is required to realize acceptable measurement accuracy. For the same reason, high optical power is required to realize acceptable signal/noise ratio. It is concluded that the technique under consideration is not feasible for the levels of aerosol concentration and size distribution to be generally encountered. (Author)

Document Details

Document Type
Technical Report
Publication Date
Nov 01, 1967
Accession Number
AD0675987

Entities

People

  • Alan Nathan
  • Arthur L. Rossoff

Tags

Communities of Interest

  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Accuracy
  • Airspeed
  • Amplitude
  • Doppler Effect
  • Errors
  • Helicopters
  • Measurement
  • Particles
  • Turbulence

Fields of Study

  • Physics

Readers

  • Atmospheric Remote Sensing.
  • Educational Psychology
  • Spectroscopy.