Observations of a Searchlight Beam to an Altitude of 28 Kilometers

E. O. Hulburt

doi:10.1364/JOSA.27.000377

Journal of the Optical Society of America
Vol. 27,
Issue 11,
pp. 377-382
(1937)
•https://doi.org/10.1364/JOSA.27.000377

Observations of a Searchlight Beam to an Altitude of 28 Kilometers

E. O. Hulburt

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E. O. Hulburt, "Observations of a Searchlight Beam to an Altitude of 28 Kilometers," J. Opt. Soc. Am. 27, 377-382 (1937)

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Abstract

The beam of a high intensity searchlight directed over an observing station 18.4 km distant at angles of 30° and 45° to the horizontal was visible to a vertical altitude of about 20 km and was photographed to 28 km on clear nights. The intensity of the beam measured from the photographs was of the same order of magnitude as that calculated from the Rayleigh theory of molecular scattering using standard tables of stratospheric densities. At 5 km the observed intensity was greater than the theoretical intensity by a factor of about 7, the factor decreasing to about unity above 10 km, as would be accounted for by a small number of haze particles at 5 km which decreased to an imperceptible amount above 10 km.

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(1)		(2)	(3)	(4)	(5)

			Intensity of Beam erg cm⁻² sec.⁻¹

Negative		Altitude	From Photograph	From Theory	Ratio (3)/(4)

E		22 km	(0.7) × 10⁻⁵	0.49 × 10⁻⁵	(1)
D	c	11.0	0.54 × 10⁻³	0.22 × 10⁻³	2.5
	b	10.4	0.54 × 10⁻³	0.24 × 10⁻³	2.3
	a	9.8	0.54 × 10⁻³	0.25 × 10⁻³	2.2
C	c	8.7	0.93 × 10⁻³	0.28 × 10⁻³	3.3
	b	8.2	1.9 × 10⁻³	0.34 × 10⁻³	5.6
	a	7.6	2.5 × 10⁻³	0.39 × 10⁻³	6.4
B	c	6.7	3.8 × 10⁻³	0.59 × 10⁻³	6.4
	b	5.8	6.3 × 10⁻³	0.94 × 10⁻³	6.7
	a	4.8	9.7 × 10⁻³	1.34 × 10⁻³	7.2

Altitude	Temp.	Density d	n
0 km	1.72°C	1256×10⁻⁶	261×10¹⁷
2	−4.16	1010	210
4	−15.3	817	170
6	−29.3	660	137
8	−43.6	529	110
10	−54.2	414	86.0
12	−55	311	64.5
14	−55	228	47.5
16	−55	167	34.7
18	−55	121	25.2
20 km	−55°C	89.7×10⁻⁶	18.6×10¹⁷
22	−55	65.8	13.7
24	−55	48.2	10.0
26	−55	35.3	7.32
28	−55	25.9	5.39
30	−55	19.0	3.95
32	−55	13.9	2.89
34	−55	10.2	2.12
36	−55	7.54	1.57
38	−55	5.53	1.15

(1)		(2)	(3)	(4)	(5)

			Intensity of Beam erg cm⁻² sec.⁻¹

Negative		Altitude	From Photograph	From Theory	Ratio (3)/(4)

E		22 km	(0.7) × 10⁻⁵	0.49 × 10⁻⁵	(1)
D	c	11.0	0.54 × 10⁻³	0.22 × 10⁻³	2.5
	b	10.4	0.54 × 10⁻³	0.24 × 10⁻³	2.3
	a	9.8	0.54 × 10⁻³	0.25 × 10⁻³	2.2
C	c	8.7	0.93 × 10⁻³	0.28 × 10⁻³	3.3
	b	8.2	1.9 × 10⁻³	0.34 × 10⁻³	5.6
	a	7.6	2.5 × 10⁻³	0.39 × 10⁻³	6.4
B	c	6.7	3.8 × 10⁻³	0.59 × 10⁻³	6.4
	b	5.8	6.3 × 10⁻³	0.94 × 10⁻³	6.7
	a	4.8	9.7 × 10⁻³	1.34 × 10⁻³	7.2

Altitude	Temp.	Density d	n
0 km	1.72°C	1256×10⁻⁶	261×10¹⁷
2	−4.16	1010	210
4	−15.3	817	170
6	−29.3	660	137
8	−43.6	529	110
10	−54.2	414	86.0
12	−55	311	64.5
14	−55	228	47.5
16	−55	167	34.7
18	−55	121	25.2
20 km	−55°C	89.7×10⁻⁶	18.6×10¹⁷
22	−55	65.8	13.7
24	−55	48.2	10.0
26	−55	35.3	7.32
28	−55	25.9	5.39
30	−55	19.0	3.95
32	−55	13.9	2.89
34	−55	10.2	2.12
36	−55	7.54	1.57
38	−55	5.53	1.15

Abstract

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Tables (2)

Equations (9)

Journal of the Optical Society of America