Abstract

This paper describes the facilities and results in an experiment to investigate light pulse propagation through atmospheric clouds. The experiments were conducted with the transmitter and receiver located on two mountain peaks in a naturally cloudy area. The transmitter was a Q-switched ruby laser producing 30 nsec light pulses. The received pulses were 1–10 μsec in duration when there was a cloud in the propagation path. The multipath time lengthening of the received pulse resulted from multiple scattering inside the cloud. The extent of this multipath pulse spreading can be shown to be comparable to that predicted from computer simulation models. We also observed a number of effects in which relatively small changes in the gross cloud shape produced a change in the received signal intensity of an order of magnitude or so.

© 1973 Optical Society of America

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References

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  1. S. Chandrasekhar, Radiative Transfer (Dover, New York, 1960).
  2. H. C. Van de Hulst, Bull Astron. Inst. Neth. 20, 77 (1968).
  3. G. N. Plass, G. W. Kattawar, App. Opt., 7, 415–419 (1968).
    [CrossRef]
  4. R. E. Danielson, D.. R. Moore, H. C. Van de Hulst, J. Atmos. Sci., 26, 1078–1087 (1968).
    [CrossRef]
  5. E. A. Bucher, Appl. Opt. 12, 2391 (1973).
    [CrossRef] [PubMed]
  6. M. Luckiesh, Astrophys. Jm 49, 108–130 (1919).
    [CrossRef]
  7. E. A. Bucher, “Multiple Scatter Propagation Models and Experiments for Optical Communication Through Clouds,” (to be published).
  8. E. A. Bucher, R. M. Lerner, C. W. Niessen, Proc. IEEE, 58, 1564–1567 (1970).
    [CrossRef]
  9. R. M. Lerner, Appl. Opt., 10, 1914–1918 (1971).
    [CrossRef] [PubMed]
  10. R. M. Lerner, “Dynamic Gain Control for Optical Radar,” to be published.
  11. B. J. Mason, Clouds, Rain and Rainmaking (Cambridge University Press, London, 1962), pp. 1–16.
  12. W. Howell, Mt. Washington Observatory, private communication.
  13. R. J. Brun et al., “Impingement of Cloud Droplets on a Cylinder and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method,” NACA TR-125, Lewis Flight Propulsion Laboratory, Cleveland, Ohio (1955).
  14. H. C. Van de Hulst, Light Scattering by Small Particles (Wiley, New York, (1957).

1973

1971

1970

E. A. Bucher, R. M. Lerner, C. W. Niessen, Proc. IEEE, 58, 1564–1567 (1970).
[CrossRef]

1968

H. C. Van de Hulst, Bull Astron. Inst. Neth. 20, 77 (1968).

G. N. Plass, G. W. Kattawar, App. Opt., 7, 415–419 (1968).
[CrossRef]

R. E. Danielson, D.. R. Moore, H. C. Van de Hulst, J. Atmos. Sci., 26, 1078–1087 (1968).
[CrossRef]

1919

M. Luckiesh, Astrophys. Jm 49, 108–130 (1919).
[CrossRef]

Brun, R. J.

R. J. Brun et al., “Impingement of Cloud Droplets on a Cylinder and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method,” NACA TR-125, Lewis Flight Propulsion Laboratory, Cleveland, Ohio (1955).

Bucher, E. A.

E. A. Bucher, Appl. Opt. 12, 2391 (1973).
[CrossRef] [PubMed]

E. A. Bucher, R. M. Lerner, C. W. Niessen, Proc. IEEE, 58, 1564–1567 (1970).
[CrossRef]

E. A. Bucher, “Multiple Scatter Propagation Models and Experiments for Optical Communication Through Clouds,” (to be published).

Chandrasekhar, S.

S. Chandrasekhar, Radiative Transfer (Dover, New York, 1960).

Danielson, R. E.

R. E. Danielson, D.. R. Moore, H. C. Van de Hulst, J. Atmos. Sci., 26, 1078–1087 (1968).
[CrossRef]

Howell, W.

W. Howell, Mt. Washington Observatory, private communication.

Kattawar, G. W.

G. N. Plass, G. W. Kattawar, App. Opt., 7, 415–419 (1968).
[CrossRef]

Lerner, R. M.

R. M. Lerner, Appl. Opt., 10, 1914–1918 (1971).
[CrossRef] [PubMed]

E. A. Bucher, R. M. Lerner, C. W. Niessen, Proc. IEEE, 58, 1564–1567 (1970).
[CrossRef]

R. M. Lerner, “Dynamic Gain Control for Optical Radar,” to be published.

Luckiesh, M.

M. Luckiesh, Astrophys. Jm 49, 108–130 (1919).
[CrossRef]

Mason, B. J.

B. J. Mason, Clouds, Rain and Rainmaking (Cambridge University Press, London, 1962), pp. 1–16.

Moore, D.. R.

R. E. Danielson, D.. R. Moore, H. C. Van de Hulst, J. Atmos. Sci., 26, 1078–1087 (1968).
[CrossRef]

Niessen, C. W.

E. A. Bucher, R. M. Lerner, C. W. Niessen, Proc. IEEE, 58, 1564–1567 (1970).
[CrossRef]

Plass, G. N.

G. N. Plass, G. W. Kattawar, App. Opt., 7, 415–419 (1968).
[CrossRef]

Van de Hulst, H. C.

R. E. Danielson, D.. R. Moore, H. C. Van de Hulst, J. Atmos. Sci., 26, 1078–1087 (1968).
[CrossRef]

H. C. Van de Hulst, Bull Astron. Inst. Neth. 20, 77 (1968).

H. C. Van de Hulst, Light Scattering by Small Particles (Wiley, New York, (1957).

App. Opt.

G. N. Plass, G. W. Kattawar, App. Opt., 7, 415–419 (1968).
[CrossRef]

Appl. Opt.

Astrophys. Jm

M. Luckiesh, Astrophys. Jm 49, 108–130 (1919).
[CrossRef]

Bull Astron. Inst. Neth.

H. C. Van de Hulst, Bull Astron. Inst. Neth. 20, 77 (1968).

J. Atmos. Sci.

R. E. Danielson, D.. R. Moore, H. C. Van de Hulst, J. Atmos. Sci., 26, 1078–1087 (1968).
[CrossRef]

Proc. IEEE

E. A. Bucher, R. M. Lerner, C. W. Niessen, Proc. IEEE, 58, 1564–1567 (1970).
[CrossRef]

Other

E. A. Bucher, “Multiple Scatter Propagation Models and Experiments for Optical Communication Through Clouds,” (to be published).

S. Chandrasekhar, Radiative Transfer (Dover, New York, 1960).

R. M. Lerner, “Dynamic Gain Control for Optical Radar,” to be published.

B. J. Mason, Clouds, Rain and Rainmaking (Cambridge University Press, London, 1962), pp. 1–16.

W. Howell, Mt. Washington Observatory, private communication.

R. J. Brun et al., “Impingement of Cloud Droplets on a Cylinder and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method,” NACA TR-125, Lewis Flight Propulsion Laboratory, Cleveland, Ohio (1955).

H. C. Van de Hulst, Light Scattering by Small Particles (Wiley, New York, (1957).

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Figures (22)

Fig. 1
Fig. 1

Sketch of propagation link.

Fig. 2
Fig. 2

Schematic diagram of transmitter site equipment.

Fig. 3
Fig. 3

Schematic diagram of receiver site equipment.

Fig. 4
Fig. 4

Photograph of receiver shelter on Wildcat Mountain showing microwave, radiotelephone and two-way radio antennas.

Fig. 5
Fig. 5

Interior view of the receiver site showing probe receiver in right lower foreground, boresight receiver in center background, and lidar transmitter above boresight receiver.

Fig. 6
Fig. 6

(a). Formation of an idealized orographic cap cloud; (b). formation of turbulent cap cloud.

Fig. 7
Fig. 7

Received signals observed during transition from clear to cloudy conditions.

Fig. 8
Fig. 8

Signal received during an opening.

Fig. 9
Fig. 9

Photograph shows turbulence scale for clouds observed on the link.

Fig. 10
Fig. 10

Received signals illustrating a hot spot.

Fig. 11
Fig. 11

Received signals illustrating a wisp fade.

Fig. 12
Fig. 12

Sketch of cloud conditions leading to a wisp fade.

Fig. 13
Fig. 13

Received signals illustrating side losses.

Fig. 14
Fig. 14

Sketch of cloud conditions during side losses.

Fig. 15
Fig. 15

Sketch of link geometry during a cap cloud.

Fig. 16
Fig. 16

Signals received as probe receiver scans vertically along the line-of-sight with a cap cloud.

Fig. 17
Fig. 17

Signals received as probe receiver scans horizontally along the leading edge of a cap cloud.

Fig. 18
Fig. 18

Azimuth scan showing uniformity of signal inside cloud in an undercast.

Fig. 19
Fig. 19

Elevation scan showing change in received signal inside undercast as probe receiver scans.

Fig. 20
Fig. 20

Sketch of link geometry during an undercast.

Fig. 21
Fig. 21

Received signal level as the transmitter scans in elevation with the receiver in undercast.

Fig. 22
Fig. 22

Received signal level as transmitter scans horizontally in undercast.

Tables (3)

Tables Icon

Table I Estimated Exit Spot Size on Cloud Top for Various Cap Clouds

Tables Icon

Table II Calculated and Measured Multipath Time Spreading for Cap Clouds

Tables Icon

Table III Calculated and Measured Multipath Time Spreading for Undercast Clouds

Equations (13)

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Δ t = ( 0.74 τ d 0.82 ) / c ,
τ d = T / D d ;
D d = D / ( 1 - cos θ ) ,
1 / D = γ = Q ext N π r 2 ,
τ d = N π r 2 Q ext ( 1 - cos θ ) T
τ d = 0 T N π r 2 Q ext ( 1 - cos θ ) d t ,
L W C ( t ) = L W C 0 [ 1 - ( t / T ) ] ,
r ( t ) = r 0 [ 1 - ( t / T ) ] 1 / 3 .
( 4 π / 3 ) N r 0 3 ρ w = L W C 0 ,
τ d = 0 T N π r 0 2 [ 1 - ( t / T ) ] 2 / 3 Q ext ( 1 - cos θ ) d t .
τ d = 0.6 N π r 0 2 Q ext ( 1 - cos θ )     T .
τ d = 0.6 × [ ( 0.75 L W C 0 ) / r 0 ρ w ] × Q ext ( 1 - cos θ ) T = 0.45 [ ( L W C 0 Q ext ( 1 - cos θ ) T / ( r 0 ρ w ) ] .
τ d = [ ( 0.45 S L W C 0 Q ext ( 1 - cos θ ) T / ( ρ w r 0 ) ] .

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