Abstract

The Doppler shift of light from a rapidly rotating or rapidly flowing source limits the spectroscopic resolution with which it can be studied using Fabry-Perot spectrometers that have the usual axial fringe adjustment. Because of the angular dependence of the wavenumber transmitted by the Fabry-Perot, the entrance aperture can be positioned off-axis at an angle chosen such that the wavenumber shift across the entrance aperture matches the shift presented by the source, thereby compensating for the Doppler effect. The principle can be extended to the Michelson interferometer for Fourier transform spectroscopy when the Michelson is used without field compensation. High resolution spectra obtained with a PEP-SIOS spectrometer using the entire disk of Jupiter, a rapidly rotating planet, are presented as an example.

© 1972 Optical Society of America

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References

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  1. T. J. Deeming, L. M. Trafton, Appl. Opt. 10, 382 (1971).
    [CrossRef] [PubMed]
  2. J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett. 18, 368 (1971); J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett 18, 477 (1971).
    [CrossRef]
  3. P. Jacquinot, J. Opt. Soc. Am. 44, 761 (1954).
    [CrossRef]
  4. J. E. Mack, D. P. McNutt, F. L. Roesler, R. Chabbal, Appl. Opt. 2, 873 (1963).
  5. F. L. Roesler, J. E. Mack, J. Phys. 28, Suppl. 22, 313 (1967).
  6. D. P. McNutt, J. Opt. Soc. Am. 55, 288 (1965).
    [CrossRef]
  7. M. Minnaert, G. F. W. Mulders, J. Houtgast, Photometric Atlas of the Solar Spectrum (D. Schnabel, Kampert & Helm, Amsterdam, 1940).

1971 (2)

J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett. 18, 368 (1971); J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett 18, 477 (1971).
[CrossRef]

T. J. Deeming, L. M. Trafton, Appl. Opt. 10, 382 (1971).
[CrossRef] [PubMed]

1967 (1)

F. L. Roesler, J. E. Mack, J. Phys. 28, Suppl. 22, 313 (1967).

1965 (1)

1963 (1)

1954 (1)

Chabbal, R.

Deeming, T. J.

Houtgast, J.

M. Minnaert, G. F. W. Mulders, J. Houtgast, Photometric Atlas of the Solar Spectrum (D. Schnabel, Kampert & Helm, Amsterdam, 1940).

Jacquinot, P.

Leavitt, J. A.

J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett. 18, 368 (1971); J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett 18, 477 (1971).
[CrossRef]

Mack, J. E.

F. L. Roesler, J. E. Mack, J. Phys. 28, Suppl. 22, 313 (1967).

J. E. Mack, D. P. McNutt, F. L. Roesler, R. Chabbal, Appl. Opt. 2, 873 (1963).

McNutt, D. P.

Minnaert, M.

M. Minnaert, G. F. W. Mulders, J. Houtgast, Photometric Atlas of the Solar Spectrum (D. Schnabel, Kampert & Helm, Amsterdam, 1940).

Mulders, G. F. W.

M. Minnaert, G. F. W. Mulders, J. Houtgast, Photometric Atlas of the Solar Spectrum (D. Schnabel, Kampert & Helm, Amsterdam, 1940).

Roesler, F. L.

F. L. Roesler, J. E. Mack, J. Phys. 28, Suppl. 22, 313 (1967).

J. E. Mack, D. P. McNutt, F. L. Roesler, R. Chabbal, Appl. Opt. 2, 873 (1963).

Stoner, J. O.

J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett. 18, 368 (1971); J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett 18, 477 (1971).
[CrossRef]

Trafton, L. M.

Appl. Opt. (2)

Appl. Phys. Lett. (1)

J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett. 18, 368 (1971); J. O. Stoner, J. A. Leavitt, Appl. Phys. Lett 18, 477 (1971).
[CrossRef]

J. Opt. Soc. Am. (2)

J. Phys. (1)

F. L. Roesler, J. E. Mack, J. Phys. 28, Suppl. 22, 313 (1967).

Other (1)

M. Minnaert, G. F. W. Mulders, J. Houtgast, Photometric Atlas of the Solar Spectrum (D. Schnabel, Kampert & Helm, Amsterdam, 1940).

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Figures (7)

Fig. 1
Fig. 1

Geometry of the off-axis Fabry-Perot spectrometer showing the etalon axis tipped away from the spectrometer axis by an angle ϕ in the x direction.

Fig. 2
Fig. 2

Principle of the Doppler-compensating interferometer. The source is imaged on an aperture displaced from the interferometer axis, as indicated in (b) by the relative positions of the aperture and interference fringes. The linear Doppler shift across the source image (a) is approximated by the shift (c) in the passband of the instrument. The slight mismatch remaining between source and instrument over the aperture is essentially the same as that present with the usual alignment of the interferometer for a stationary source.

Fig. 3
Fig. 3

Diagram of the PEPSIOS spectrometer showing the addition of an image rotator, coupling lens, and aperture slide to facilitate Doppler compensation.

Fig. 4
Fig. 4

Calculated instrumental passband for the off-axis PEPSIOS. The passband for spectral lines of Jovian origin (a) is identical to that for a conventional PEPSIOS with a nonrotating source. The passbands for solar and terrestrial lines in the Jovian spectrum with (b) a uniformly illuminated source and (c) a limb-darkened source are shown for comparison.

Fig. 5
Fig. 5

Comparison of the solar spectrum taken from the Utrecht solar atlas7 and a Jovain scan taken with the Doppler-compensating PEPSIOS. The narrow line in the PEPSIOS scan is due to molecular hydrogen on Jupiter, while the broad features are reflected solar lines.

Fig. 6
Fig. 6

Comparison of the Utrecht solar spectrum7 with Jovian and lunar scans taken with the Doppler-compensating PEPSIOS. The lunar scan illustrates the broadening of terrestrial and solar lines for a uniformly illuminated source and the Jovian scans exhibit broadening due to a limb-darkened source. A terrestrial water vapor line at 6565.5 Å is flattened by the Doppler-compensating instrument so that a blended molecular hydrogen line of Jovian origin may be unambiguously identified in the Jovian scans.

Fig. 7
Fig. 7

Relation between limiting resolution and angular field of view for a PEPSIOS spectrometer with various combinations of etalon and telescope diameters. Each combination may be used, without utilizing its full capacity, anywhere in the region to the left of the corresponding line.

Equations (7)

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a = [ 1 + 4 N 2 π - 2 sin 2 ( 2 π n l σ cos θ ) ] - 1 ,
cos θ = [ 1 + ( x / f ) tan ϕ ] cos ϕ cos θ .
= cos ϕ [ 1 + ( x tan ϕ / f ) ] / ( 1 - 2 v x / c d ) .
σ = σ 0 ( 1 - v 2 / c 2 ) 1 2 / ( 1 + ψ v / c ) ,
δ = ( d F P / d T ) β = ( d F P / d T ) ( 8 / 1.31 R ) 1 2 .
U g = τ g ( π β 2 / 4 ) A g cos α = 4 π τ g A g [ R 2 + R c 2 / v 2 ] - 1 2 .
U p = τ p ( π β 2 / 4 ) A F P = ( 1.5 π ) τ p A F P / R .

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