Abstract

Solar millimeter radiation, isolated by black filters, was received with a thermal detector in the focus of a 60-in parabola. The transmission of this radiation through woven copper wire mesh of various gauge was measured. Since neither theoretical nor experimental data on the filter characteristics of mesh were available, a microwave method was used to obtain this information. The resulting filter curves together with the solar measurements made an evaluation of the millimeter spectrum possible.

Also, a theoretical spectral curve was drawn multiplying Rayleigh-Jeans’ λ−4 intensity with Van Vleck attentuation data which were computed for the atmospheric conditions during the solar measurements, but raised according to earlier experimental attenuation results of the authors. This curve was in good agreement with the measured spectrum showing that the observed short-wave cutoff near 0.9 mm is due to sharply rising attenuation; the observed peak between 1.0 and 1.1 mm lies in the predicted window, after which the spectral intensity falls off at longer wavelengths according to the λ−4 law.

© 1956 Optical Society of America

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References

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  1. Proceedings of the Symposium on Electromagnetic Wave Theory, June, 1955; Inst. Radio Engrs. Transactions on Antennas and Propagation, Vol.  AP-4, No. 3, July, 1956, p. 582 (see App. A2–9). A more detailed account was given in J. Appl. Phys. 27, 538 (1956).
  2. William M. Sinton, Phys. Rev. 86, 424 (1952), Fig. 2.
    [Crossref]
  3. R. Bowling Barnes, Phys. Rev. 39, 562 (1932), Fig. 7.
    [Crossref]
  4. G. K. T. Conn, Proc. Cambridge Phil. Soc. 48, 240 (1947).
    [Crossref]
  5. W. Wessel, ZS Hochfr. & El. Ak. 54, 62 (1939); Pursley, Deibel, and Peters, (March, 1953), Proj. 2083, Fig. 2.
  6. C. Schaefer and M. Laugwitz, Ann. Physik 23, 951 (1907); R. Gans, Ann. Physik. 61, 447 (1920); C. Schaefer, Ann. Physik 74, 275 (1924).
    [Crossref]
  7. J. H. Van Vleck and V. F. Weisskopf, Revs. Modern Phys. 17, 227 (1945); J. H. Van Vleck, Phys. Rev. 71, 425 (1947).
    [Crossref]
  8. T. F. Rogers, , (October, 1951); R. G. Newton and T. F. Rogers, (November, 1953); Atmospheric absorption graphs presented by T. F. Rogers at the Navy Millimeter Wave Conference in Washington, D. C., 1953 (unpublished).
  9. See the abstracts of the Washington, D. C. meeting, April 28–30, 1955[Phys. Rev. 99, 605 (1955)]. The presentation of the paper was however, postponed to the URSI-Michigan Symposium (June, 1955).
  10. W. M. Sinton, J. Opt. Soc. Am.45, 975 (1955) (submitted for publication May 23, 1955).

1952 (1)

William M. Sinton, Phys. Rev. 86, 424 (1952), Fig. 2.
[Crossref]

1947 (1)

G. K. T. Conn, Proc. Cambridge Phil. Soc. 48, 240 (1947).
[Crossref]

1945 (1)

J. H. Van Vleck and V. F. Weisskopf, Revs. Modern Phys. 17, 227 (1945); J. H. Van Vleck, Phys. Rev. 71, 425 (1947).
[Crossref]

1939 (1)

W. Wessel, ZS Hochfr. & El. Ak. 54, 62 (1939); Pursley, Deibel, and Peters, (March, 1953), Proj. 2083, Fig. 2.

1932 (1)

R. Bowling Barnes, Phys. Rev. 39, 562 (1932), Fig. 7.
[Crossref]

1907 (1)

C. Schaefer and M. Laugwitz, Ann. Physik 23, 951 (1907); R. Gans, Ann. Physik. 61, 447 (1920); C. Schaefer, Ann. Physik 74, 275 (1924).
[Crossref]

Bowling Barnes, R.

R. Bowling Barnes, Phys. Rev. 39, 562 (1932), Fig. 7.
[Crossref]

Conn, G. K. T.

G. K. T. Conn, Proc. Cambridge Phil. Soc. 48, 240 (1947).
[Crossref]

Laugwitz, M.

C. Schaefer and M. Laugwitz, Ann. Physik 23, 951 (1907); R. Gans, Ann. Physik. 61, 447 (1920); C. Schaefer, Ann. Physik 74, 275 (1924).
[Crossref]

Rogers, T. F.

T. F. Rogers, , (October, 1951); R. G. Newton and T. F. Rogers, (November, 1953); Atmospheric absorption graphs presented by T. F. Rogers at the Navy Millimeter Wave Conference in Washington, D. C., 1953 (unpublished).

Schaefer, C.

C. Schaefer and M. Laugwitz, Ann. Physik 23, 951 (1907); R. Gans, Ann. Physik. 61, 447 (1920); C. Schaefer, Ann. Physik 74, 275 (1924).
[Crossref]

Sinton, W. M.

W. M. Sinton, J. Opt. Soc. Am.45, 975 (1955) (submitted for publication May 23, 1955).

Sinton, William M.

William M. Sinton, Phys. Rev. 86, 424 (1952), Fig. 2.
[Crossref]

Van Vleck, J. H.

J. H. Van Vleck and V. F. Weisskopf, Revs. Modern Phys. 17, 227 (1945); J. H. Van Vleck, Phys. Rev. 71, 425 (1947).
[Crossref]

Weisskopf, V. F.

J. H. Van Vleck and V. F. Weisskopf, Revs. Modern Phys. 17, 227 (1945); J. H. Van Vleck, Phys. Rev. 71, 425 (1947).
[Crossref]

Wessel, W.

W. Wessel, ZS Hochfr. & El. Ak. 54, 62 (1939); Pursley, Deibel, and Peters, (March, 1953), Proj. 2083, Fig. 2.

Ann. Physik (1)

C. Schaefer and M. Laugwitz, Ann. Physik 23, 951 (1907); R. Gans, Ann. Physik. 61, 447 (1920); C. Schaefer, Ann. Physik 74, 275 (1924).
[Crossref]

Phys. Rev. (2)

William M. Sinton, Phys. Rev. 86, 424 (1952), Fig. 2.
[Crossref]

R. Bowling Barnes, Phys. Rev. 39, 562 (1932), Fig. 7.
[Crossref]

Proc. Cambridge Phil. Soc. (1)

G. K. T. Conn, Proc. Cambridge Phil. Soc. 48, 240 (1947).
[Crossref]

Revs. Modern Phys. (1)

J. H. Van Vleck and V. F. Weisskopf, Revs. Modern Phys. 17, 227 (1945); J. H. Van Vleck, Phys. Rev. 71, 425 (1947).
[Crossref]

ZS Hochfr. & El. Ak. (1)

W. Wessel, ZS Hochfr. & El. Ak. 54, 62 (1939); Pursley, Deibel, and Peters, (March, 1953), Proj. 2083, Fig. 2.

Other (4)

T. F. Rogers, , (October, 1951); R. G. Newton and T. F. Rogers, (November, 1953); Atmospheric absorption graphs presented by T. F. Rogers at the Navy Millimeter Wave Conference in Washington, D. C., 1953 (unpublished).

See the abstracts of the Washington, D. C. meeting, April 28–30, 1955[Phys. Rev. 99, 605 (1955)]. The presentation of the paper was however, postponed to the URSI-Michigan Symposium (June, 1955).

W. M. Sinton, J. Opt. Soc. Am.45, 975 (1955) (submitted for publication May 23, 1955).

Proceedings of the Symposium on Electromagnetic Wave Theory, June, 1955; Inst. Radio Engrs. Transactions on Antennas and Propagation, Vol.  AP-4, No. 3, July, 1956, p. 582 (see App. A2–9). A more detailed account was given in J. Appl. Phys. 27, 538 (1956).

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Figures (9)

Fig. 1
Fig. 1

Schematic of solar detection apparatus showing reflection of incident radiation from parabola to wobbling mirror to Golay cell.

Fig. 2
Fig. 2

Setup for measurement of transmission of wire mesh for a parallel microwave beam.

Fig. 3
Fig. 3

Measured transmission characteristics t(λ/d) of woven copper wire mesh for two parameters d/a; d=wire spacing; a=wire radius.

Fig. 4
Fig. 4

Demonstration that transmission of screens for a given parameter d/a depends only on the ratio λ/d. Numbers at the various points indicate m=1/d in inches−1. □ denotes λ=4.3 mm; O and X denote λ in the 8.6-mm range. Separation of points with same d is due to the selection of slightly different wavelengths in the 8.6-mm region.

Fig. 5
Fig. 5

Mesh transmission Tm obtained during low humidity conditions with the solar detection apparatus. Splitting of curve is due to variations in the parameter d/a.

Fig. 6
Fig. 6

Graphical representation of the filtering action of the screens on the solar spectrum. The mesh transmission characteristics tm(λ) of various mesh are plotted together with a possible spectrum I(λ). The resultant transmission Tm is determined by the product of the two curves.

Fig. 7
Fig. 7

A: trial assumption for spectrum. B, C, D, E: successive improvements. Top insert: corresponding errors plotted for each screen. E, beyond which errors could not be reduced, is considered a solution.

Fig. 8
Fig. 8

A: trial assumption for spectrum. B, C, D: successive improvements. Top insert: corresponding errors plotted for each screen. D, beyond which errors could not be reduced, is considered a solution.

Fig. 9
Fig. 9

Thin line curves: various solutions obtained in the way shown in Figs. 7 and 8. Top insert: errors for various solutions. Heavy curve: Rayleigh-Jeans λ−4 intensity modified by Van Vleck attenuation.

Tables (4)

Tables Icon

Table I Meteorological data for ground level and various altitudes at the time solar mesh transmissions (Fig. 5) were measured.

Tables Icon

Table II Mesh numbers m and d/a parameters of mesh used in solar experiment and solar transmissions Tm obtained with them.

Tables Icon

Table III Measured transmission coefficients am, bm⋯ extracted from Fig. 4 for the 10 fixed wavelengths λi and 13 mesh numbers m listed and interpolated for proper d/a parameters as used in solar experiment (listed in Table II).

Tables Icon

Table IV First approximation leading from double-step curve A to improved curve B in Fig. 7. Curve A: Ii), normalized: Ei. Curve B: I′(λi), normalized: Ei′. am, bm⋯: mesh transmission coefficients from Table III. ∑m: sum of columns. Tm: solar mesh transmission from Table II and Fig. 5. Δm=∑mTm: errors. Heavy outlined: numbers most contributing to ∑m. ϕ: improving factors. ϕAv=improving factors averaged over the length of the outlined structure in the corresponding line.

Equations (6)

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T m = 0 I ( λ ) t m ( λ ) d λ 0 I ( λ ) d λ .
t m ( λ 1 ) = a m ; t m ( λ 2 ) = b m ;             etc. I ( λ 1 ) Δ λ 1 i I ( λ i ) Δ λ i = E 1 ; I ( λ 2 ) Δ λ 2 i I ( λ i ) Δ λ i = E 2 ;             etc., }
i E i = 1 ,
T m = a m E 1 + b m E 2 + .
Δ m = a m E 1 + b m E 2 + - T m .
ρ % = 100 ( Δ 70 + Δ 50 + + Δ 3.5 ) / 13