Abstract

The Lyman Far Ultraviolet Spectrographic Explorer telescope is a Wolter type II glancing incidence design with an aperture of 64 cm. Because the spacecraft is required to guide on stars fainter than mν = 16, a visible light baffle is necessary to protect the field of view from the stray light that results from out-of-field bright sources. Such a baffle system is described here. Total point-source transmittances are computed for incident beams in the range 0–70°. Estimates for background brightness on the detector are made for the contribution from direct sunlight and earthshine. Scattering from the black surfaces of the baffle, the vanes, and diffraction at the structure's edges are taken into consideration.

© 1993 Optical Society of America

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References

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  1. J. F. Osantowski, P. M. Davila, T. Saha, “Telescope technology for the Far Ultraviolet Spectrographic Explorer (FUSE),” Opt. Eng. 25, 1039–1044 (1986).
  2. R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
    [CrossRef]
  3. C. Morbey, “Optical design of two spectrographs for the Canada-France-Hawaii telescope,” Appl. Opt. 31, 2291–2300 (1992).
    [CrossRef] [PubMed]
  4. “Lyman, The Far Ultraviolet Spectrographs Explorer,” Rep. NAS5-30339 (NASA, Washington, D.C., 1990).
  5. T. T. Saha, “General surface equations for glancing incidence telescopes,” Appl. Opt. 26, 658–663 (1987).
    [CrossRef] [PubMed]
  6. J. D. Mangus, “Strategy and calculations for the design of baffles for Wolter Type II telescopes,” in Grazing Incidence Optics for Astronomical and Laboratory Applications, S. Bowyer, ed., Proc. Soc. Photo-Opt. Instrum. Eng.830, 245–253 (1987).
  7. B. K. Likeness, “Stray light simulations with advanced Monte Carlo techniques,” in Stray Light Problems in Optical Systems, J. D. Lytle, H. E. Morrow, eds., Proc. Soc. Photo-Opt. Instrum. Eng.107, 80–88 (1977).

1992 (1)

1987 (1)

1986 (1)

J. F. Osantowski, P. M. Davila, T. Saha, “Telescope technology for the Far Ultraviolet Spectrographic Explorer (FUSE),” Opt. Eng. 25, 1039–1044 (1986).

1969 (1)

R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
[CrossRef]

Davila, P. M.

J. F. Osantowski, P. M. Davila, T. Saha, “Telescope technology for the Far Ultraviolet Spectrographic Explorer (FUSE),” Opt. Eng. 25, 1039–1044 (1986).

Giacconi, R.

R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
[CrossRef]

Likeness, B. K.

B. K. Likeness, “Stray light simulations with advanced Monte Carlo techniques,” in Stray Light Problems in Optical Systems, J. D. Lytle, H. E. Morrow, eds., Proc. Soc. Photo-Opt. Instrum. Eng.107, 80–88 (1977).

Mangus, J. D.

J. D. Mangus, “Strategy and calculations for the design of baffles for Wolter Type II telescopes,” in Grazing Incidence Optics for Astronomical and Laboratory Applications, S. Bowyer, ed., Proc. Soc. Photo-Opt. Instrum. Eng.830, 245–253 (1987).

Morbey, C.

Osantowski, J. F.

J. F. Osantowski, P. M. Davila, T. Saha, “Telescope technology for the Far Ultraviolet Spectrographic Explorer (FUSE),” Opt. Eng. 25, 1039–1044 (1986).

Reidy, W. P.

R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
[CrossRef]

Saha, T.

J. F. Osantowski, P. M. Davila, T. Saha, “Telescope technology for the Far Ultraviolet Spectrographic Explorer (FUSE),” Opt. Eng. 25, 1039–1044 (1986).

Saha, T. T.

Vaiana, G. S.

R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
[CrossRef]

Van Speybroeck, L. P.

R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
[CrossRef]

Zehnpfennig, T. F.

R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
[CrossRef]

Appl. Opt. (2)

Opt. Eng. (1)

J. F. Osantowski, P. M. Davila, T. Saha, “Telescope technology for the Far Ultraviolet Spectrographic Explorer (FUSE),” Opt. Eng. 25, 1039–1044 (1986).

Space Sci. Rev. (1)

R. Giacconi, W. P. Reidy, G. S. Vaiana, L. P. Van Speybroeck, T. F. Zehnpfennig, “Grazing-incidence telescopes for x-ray astronomy,” Space Sci. Rev. 9, 3–57 (1969).
[CrossRef]

Other (3)

“Lyman, The Far Ultraviolet Spectrographs Explorer,” Rep. NAS5-30339 (NASA, Washington, D.C., 1990).

J. D. Mangus, “Strategy and calculations for the design of baffles for Wolter Type II telescopes,” in Grazing Incidence Optics for Astronomical and Laboratory Applications, S. Bowyer, ed., Proc. Soc. Photo-Opt. Instrum. Eng.830, 245–253 (1987).

B. K. Likeness, “Stray light simulations with advanced Monte Carlo techniques,” in Stray Light Problems in Optical Systems, J. D. Lytle, H. E. Morrow, eds., Proc. Soc. Photo-Opt. Instrum. Eng.107, 80–88 (1977).

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Figures (13)

Fig. 1
Fig. 1

Optical layout of (a) Lyman telescope, (b) Lyman FUSE slit farm and diverting mirror, and (c) Lyman FUSE FES camera.

Fig. 2
Fig. 2

Schematic of Lyman FUSE baffle system showing representative scattering.

Fig. 3
Fig. 3

Diffracted ray from edge point (z1, y1) on baffle to observation point (z2, y2) on telescope mirror.

Fig. 4
Fig. 4

Representative diffracted rays within the Lyman FUSE telescope–baffle system.

Fig. 5
Fig. 5

Representative light paths of scattered light within the Lyman FUSE telescope–baffle system.

Fig. 6
Fig. 6

Baseline baffle design: (a) PST function. TIS of black paints 0.05; BRDF of optical surfaces (0.057–1.2) sr−1. (b) With midbaffle PST function. TIS of black paints 0.05; BRDF of optical surfaces (0.057–1.2) sr−1. (c) PST function. TIS of black paints 0.05; BRDF of optical surfaces (0.03–1.5) sr−1. (d) With 200-mm extension PST function. TIS of black paints 0.05; BRDF of optical surfaces (0.057–1.2) sr−1. (e) With slanted vanes in the main baffle PST function. TIS of black paints 0.05; BRDF of optical surfaces (0.057–1.2) sr−1. (f) PST function. TIS of black paints 0.03; BRDF of optical surfaces (0.057–1.2) sr−1.

Fig. 7
Fig. 7

Lyman FUSE at perigee. The cross-hatched area scatters sunlight toward the spacecraft. The spacecraft lies on a line between the centers of the Sun and the Earth.

Fig. 8
Fig. 8

BST (W/cm2) for Lyman FUSE at perigee. The zenith angle of the Sun is 0°.

Fig. 9
Fig. 9

BST (W/cm2) for Lyman FUSE at perigee. The zenith angle of the Sun is 47°. The peak at a horizon angle of 73° occurs when the telescope points directly at the Sun.

Fig. 10
Fig. 10

BST (W/cm2) for Lyman FUSE at apogee. The zenith angle of the Sun is 0°.

Fig. 11
Fig. 11

BST (W/cm2) for Lyman FUSE at apogee. The zenith angle of the Sun is 47°.

Fig. 12
Fig. 12

Images of a star at the FES detector as a function of field angle for random slope errors superimposed on the Lyman FUSE optical components.

Fig. 13
Fig. 13

Star images at the FES detector as a function of field angle. Relative transmittances are given in parentheses.

Tables (4)

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Table 1 Irradiances From Diffraction

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Table 2 Attenuation by Scattering

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Table 3 Noise Limits for Centroiding

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Table 4 Attenuation for Various Contamination Levels

Equations (8)

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BSDF = [ P ( s ) / Ω ( s ) ] / P ( i ) cos [ θ ( s ) ] ,
BSDF = b [ ( B B 0 ) / 0.01 ] s .
TIS = ( 4 π δ / λ ) 2 ,
I ( u ) = I / 2 { [ ½ + C ( u ) ] 2 + [ ½ + S ( u ) ] 2 } ,
d = ( z 2 y 2 / m + y 1 / m z 1 ) / ( 1 + 1 / m 2 ) 1 / 2 ,
D = [ ( z 3 z 1 ) 2 + ( y 3 y 1 ) 2 ] 1 / 2 ,
u = π d 2 / ( λ p ) ,
φ * = tan 1 ( λ / 4 π δ y ) .

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