AU6443890A - Laser radar system for the detection of clear air turbulence - Google Patents
Laser radar system for the detection of clear air turbulenceInfo
- Publication number
- AU6443890A AU6443890A AU64438/90A AU6443890A AU6443890A AU 6443890 A AU6443890 A AU 6443890A AU 64438/90 A AU64438/90 A AU 64438/90A AU 6443890 A AU6443890 A AU 6443890A AU 6443890 A AU6443890 A AU 6443890A
- Authority
- AU
- Australia
- Prior art keywords
- laser
- clear air
- laser radar
- atmosphere
- detection
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000001514 detection method Methods 0.000 title claims description 10
- 238000013528 artificial neural network Methods 0.000 claims description 3
- 230000002159 abnormal effect Effects 0.000 claims description 2
- 230000005540 biological transmission Effects 0.000 claims 1
- 238000000034 method Methods 0.000 claims 1
- 238000001228 spectrum Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 description 4
- 239000010979 ruby Substances 0.000 description 4
- 229910001750 ruby Inorganic materials 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01W—METEOROLOGY
- G01W1/00—Meteorology
- G01W2001/003—Clear air turbulence detection or forecasting, e.g. for aircrafts
Landscapes
- Investigating Or Analysing Materials By Optical Means (AREA)
- Optical Radar Systems And Details Thereof (AREA)
Description
Laser Radar System for the Detection of Clear Air
Turbulence
Field of the Invention
This invention relates to a laser radar system for the detection of clear air turbulence in which the detected laser radar image is processed by a computer, said system consisting of a laser beam generator, laser beam transmitter, appropriately filtered optical detector, image processor, control computer and display monitor.
The invention has application for the detection of clear air turbulance (CAT) in the path of both civilion and military aircraft.
Su τimary of the Prior Art
Prior art laser based CAT detection systems depended on small refractive index changes within the CAT region giving rise to a reflected signal. In experiments conducted in the United States during the early 1960's it was claimed that a ruby laser pulse transmitted from an aircraft its clear skies gave rise to very strong returns which were attributed to CAT. However, subsequent tests showed that such returns could also be produced at the boundaries of dust laiden air masses and clear air masses.
Background of the Invention The inventor has pioneered the use of lasers for the detection of clear air turbulence (CAT), an event which occurs in clear air which cannot be detected by long wavelength radar, yet when an aircraft enters a CAT region it can shake the whole
aircraft at least, and lead to a catastrophic situation at worse, with high flying aircraft known to descend very rapidly for thousands of feet and crash onto airfields if they enter CAT caused, for example, by a previous aircraft landing. In 1964, an effort was made to resolve the issue by the inventor taking a ruby laser ranging system to the Royal Radar Establishments' airfield in the U.K. Using one of the jet engines of a Canberra jet bomber as the means of producing a region of intense turbulence, about 14 feet behind the jet engine, ruby laser pulses ι o were fired through this highly turbulent region without a trace of a return signal being detected on the laser ranging system used, despite the fact that the Rayleigh back scatter was clearly visible together with a very large signal off the tail of the Canberra bomber when the aiming point was moved from the turbulence to a
15 small spot on the bombers' tail.
This invention has much greater sophistication than was available in the prior art in that it is a laser radar system rather than a laser ranging system. Furthermore, it makes the best possible use of the fact that laser light back scatters as a laser
20 pulse propagates through the atmosphere due to the Rayleigh effect which increases as the fourth power of the wavelength. Thus, the shorter the wavelength of the transmitter laser beam, the larger the amount that is back scattered. Also, to avoid the very large Rayleigh back scatter that is picked up near the transmitter
25 aperture in a coaxial system, the present invention is gated so that the detector is not operative at maximum sensitivity as the pulse propagates near the said system. Using the logarithmic
amplification of the detected return signal, it is possible to gate the return signals so that only designated sectors of the atmosphere are sampled at a particular time allowing for far greater sensitivities than was possible in the prior art ruby laser systems used by the inventor to pioneer the field of laser/CAT detection during the early 1960's.
Summary of the Invention
It is an object of the invention to provide a laser radar system in which a laser pulse is transmitted ahead of a flying aircraft and the light scattered back off the atmosphere at specific distances analysed so that a back scattered image can be generated in which abnormal scattering of the air molecules disturbed by clear air turbulance can be distinguished from the normal atmospheric back scattered laser light. It is an object of the invention to utilise a neural network computer to analyse the back scattered radar image and to identify any parts of the said image which could correspond to the scattering effects of clear air turbulance.
Another object of the invention is to optically gate the return signal so that only designated thicknesses of the atmosphere ahead of the plane are analysed for clear air turbulance. it is an object of the invention to utilise ultraviolet laser beams to highlight any turbulant region of the atmosphere detected using eye-safe laser beams. A better understanding of the invention may be obtained from the following considerations taken in conjunction with the
accompanying drawings which are not meant to limit the scope of the invention in any way.
Figure 1 shows a short wavelength laser beam transmitted ahead of the flight path of an aircraft in clear air with the Rayleigh 5 back scatter being directed back towards said aircraft and detected, giving a smooth image.
Figure 2 shows the increased Rayleigh back scatter activity that occurs when a region of clear air turbulence exists along the flight path of the aircraft. Now the scattered image can be ι o detected and related to the CAT activity ahead so that the aircraft can take evasive action.
Figure 3 shows the basic layout of the invention.
Detailed Description of the Drawings
In Figure 1 , numeral 1 indicates the aircraft with its laser 15 radar system indicated by numeral 2 transmitting a short wavelength laser output beam, indicated by numeral 3, along its flight path without encountering any CAT as indicated by the back scattered image indicated by numeral 4.
In Figure 2, numeral 5 indicates a layer of clear air turbulence 20 (CAT) along the flight path of the aircraft which experiences the Rayleigh back scattered image indicated by numeral 6 detected and processed by laser radar system 2, allowing plane 1 to take evasive action so as to avoid the CAT 5.
In Figure 3, numeral 7 indicates the laser radar power supply 25 whilst numeral 8 indicates the laser beam generator. Numeral 9 indicates a laser beam scanner whilst numeral 10 indicates a laser
beam profile detector. Numeral 11 indicates the laser beam propagated into clear air whilst numeral 12 indicates the Rayleigh back scatter which provides a gated image of the scattering properties of selected regions of the atmosphere ahead. Numeral
5 13 indicates the gated optical detector of the invention whilst numeral 14 indicates both the control and image processing computer, in a preferred mode, a neural network computer, whilst numeral 15 indicates a display monitor on which the image of the back scattered return from the CAT region can be compared with ι o that of the outgoing laser beam.
The invention has application in the detection of clear air turbulence allowing the plane to divert from its flight path to avoid any detected CAT regions.
The invention also has application in the detection of 5 turbulence in any fluid medium.
Claims (1)
- claim,1 ) A laser radar system for the detection of clear air turbulance ahead of a flying aircraft, said system consisting of: a) A laser radar transmitter which emits a laser beam ahead of 5 the aircraft on which it is installed along its planned flight path to survey the atmosphere ahead for signs of clear air turbulance. b) A laser radar detector system which detects the atmospheric back scattered image of the transmitted laser pulse over ι o selected depths of the atmosphere in the image processing capabilities of neural network computers to identify any abnormal atmospheric scattering processes arising from clear air turbulance.2) A system as claimed in claim 1 where the transmitted laser 15 pulse wavelength is in the ultra violet region of the electromagnetic spectrum to minimise the Rayleigh scattering by the atmosphere.3) A system as claimed in claim 1 where the transmitted laser pulse wavelength is in the near infra red providing "eye safe" ι o transmission.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU64438/90A AU6443890A (en) | 1989-09-27 | 1990-09-28 | Laser radar system for the detection of clear air turbulence |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU657689 | 1989-09-27 | ||
| AUPJ6576 | 1989-09-27 | ||
| AU64438/90A AU6443890A (en) | 1989-09-27 | 1990-09-28 | Laser radar system for the detection of clear air turbulence |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| AU6443890A true AU6443890A (en) | 1991-04-28 |
Family
ID=25611865
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU64438/90A Abandoned AU6443890A (en) | 1989-09-27 | 1990-09-28 | Laser radar system for the detection of clear air turbulence |
Country Status (1)
| Country | Link |
|---|---|
| AU (1) | AU6443890A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110261874A (en) * | 2019-05-31 | 2019-09-20 | 中国科学院西安光学精密机械研究所 | Real-time clear-air bumpiness detection method and system based on coherent laser |
-
1990
- 1990-09-28 AU AU64438/90A patent/AU6443890A/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110261874A (en) * | 2019-05-31 | 2019-09-20 | 中国科学院西安光学精密机械研究所 | Real-time clear-air bumpiness detection method and system based on coherent laser |
| CN110261874B (en) * | 2019-05-31 | 2020-12-25 | 中国科学院西安光学精密机械研究所 | Real-time clear sky bump detection method and system based on coherent laser |
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