Abstract

We propose applying the techniques of spatial filtering to the concept of interferometric coronography. In such a system, provided that the object being studied is not resolved by the individual apertures of the interferometric array, the beams can be considered as coherent or, more exactly, single mode. Hence spatial filtering allows one to cleanse the beams of imperfections generated by defects on the optical components of the interferometer and thus to obtain very high rejection rates in the destructive output of the interferometer (coronographic output) for an on-axis star. Numerical simulations show that the very stringent constraints on the optical quality of a space IR interferometer aimed at detecting extrasolar planets can be relaxed to values achievable with current technology. In particular, we show that the difficulties induced by dust scattering, small micrometeorite impacts on the primary mirror, and high-frequency ripples of polishing residuals can be eliminated by simple pinhole spatial filtering. The effects, however, will be less dramatic on large-scale defects such as coating defects and pointing errors in the telescopes.

© 1997 Optical Society of America

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References

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  1. B. A. Smith, R. J. Terrile, “A circumstellar disk around Beta Pictoris,” Science 226, 1421–1424 (1984).
    [CrossRef] [PubMed]
  2. T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).
  3. J-L. Beuzit, D. Mouillet, A-M. Lagrange, J. Paufique, “Stellar coronograph for the cone-on + adaptive optics system. I. Description and performances,” Astron. Astrophys. Suppl. Ser. (1997).
    [CrossRef]
  4. J. B. Breckinridge, T. G. Kuper, R. V. Shack, “Space Telescope low-scattered-light camera: a model,” Opt. Eng. 23, 816–820 (1984).
    [CrossRef]
  5. J. R. P. Angel, “Ground-based imaging of extrasolar planets using adaptive optics,” Nature (London) 368, 203–207 (1994).
  6. R. N. Bracewell, “Detecting nonsolar planets by spinning IR interferometer,” Nature (London) 274, 780–781 (1978).
  7. J. R. P. Angel, “Use of a 16 m telescope to detect Earthlike planets,” in The Next Generation Space Telescope, P. Bély, C. Burrows, G. Illingworth, eds. (Space Telescope Science Institute, Baltimore, Md., 1989), pp. 81–88.
  8. J. R. P. Angel, N. J. Woolf, “An imaging nulling interferometer to study extrasolar planets,” Astrophys. J. 475, 373–379 (1997).
    [CrossRef]
  9. A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
    [CrossRef]
  10. A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
    [CrossRef]
  11. B. Mennesson, J-M. Mariotti, “Array configurations for a space infrared nulling interferometer dedicated to the search for Earthlike extrasolar planets,” Icarus 218 (1997).
  12. V. Coudé du Foresto, “Integrated optics in astronomical interferometry,” in Very High Angular Resolution Imaging, IAU Symposium 158, J. G. Robertson, W. J. Tango, eds. (Kluwer Academic, Dordrecht, The Netherlands, 1993).
  13. V. Coudé du Foresto, S. Ridgway, “FLUOR: A stellar interferometer using single-mode infrared fibers,” in Proceedings of ESO Meeting on High-Resolution Imaging by Interferometry II, J. M. Beckers, F. Merkle, eds. (European Southern Observatory, Garching bei München, 1991).
  14. M. Shao, M. M. Colavita, “Long-baseline optical and infrared stellar interferometry,” Ann. Rev. Astron. Astrophys. 30, 457–498 (1992).
    [CrossRef]

1997

J-L. Beuzit, D. Mouillet, A-M. Lagrange, J. Paufique, “Stellar coronograph for the cone-on + adaptive optics system. I. Description and performances,” Astron. Astrophys. Suppl. Ser. (1997).
[CrossRef]

J. R. P. Angel, N. J. Woolf, “An imaging nulling interferometer to study extrasolar planets,” Astrophys. J. 475, 373–379 (1997).
[CrossRef]

B. Mennesson, J-M. Mariotti, “Array configurations for a space infrared nulling interferometer dedicated to the search for Earthlike extrasolar planets,” Icarus 218 (1997).

1996

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

1995

A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
[CrossRef]

1994

J. R. P. Angel, “Ground-based imaging of extrasolar planets using adaptive optics,” Nature (London) 368, 203–207 (1994).

1992

M. Shao, M. M. Colavita, “Long-baseline optical and infrared stellar interferometry,” Ann. Rev. Astron. Astrophys. 30, 457–498 (1992).
[CrossRef]

1984

B. A. Smith, R. J. Terrile, “A circumstellar disk around Beta Pictoris,” Science 226, 1421–1424 (1984).
[CrossRef] [PubMed]

J. B. Breckinridge, T. G. Kuper, R. V. Shack, “Space Telescope low-scattered-light camera: a model,” Opt. Eng. 23, 816–820 (1984).
[CrossRef]

1978

R. N. Bracewell, “Detecting nonsolar planets by spinning IR interferometer,” Nature (London) 274, 780–781 (1978).

Angel, J. R. P.

J. R. P. Angel, N. J. Woolf, “An imaging nulling interferometer to study extrasolar planets,” Astrophys. J. 475, 373–379 (1997).
[CrossRef]

J. R. P. Angel, “Ground-based imaging of extrasolar planets using adaptive optics,” Nature (London) 368, 203–207 (1994).

J. R. P. Angel, “Use of a 16 m telescope to detect Earthlike planets,” in The Next Generation Space Telescope, P. Bély, C. Burrows, G. Illingworth, eds. (Space Telescope Science Institute, Baltimore, Md., 1989), pp. 81–88.

Beuzit, J-L.

J-L. Beuzit, D. Mouillet, A-M. Lagrange, J. Paufique, “Stellar coronograph for the cone-on + adaptive optics system. I. Description and performances,” Astron. Astrophys. Suppl. Ser. (1997).
[CrossRef]

Bracewell, R. N.

R. N. Bracewell, “Detecting nonsolar planets by spinning IR interferometer,” Nature (London) 274, 780–781 (1978).

Breckinridge, J. B.

J. B. Breckinridge, T. G. Kuper, R. V. Shack, “Space Telescope low-scattered-light camera: a model,” Opt. Eng. 23, 816–820 (1984).
[CrossRef]

Colavita, M. M.

M. Shao, M. M. Colavita, “Long-baseline optical and infrared stellar interferometry,” Ann. Rev. Astron. Astrophys. 30, 457–498 (1992).
[CrossRef]

Coudé du Foresto, V.

V. Coudé du Foresto, “Integrated optics in astronomical interferometry,” in Very High Angular Resolution Imaging, IAU Symposium 158, J. G. Robertson, W. J. Tango, eds. (Kluwer Academic, Dordrecht, The Netherlands, 1993).

V. Coudé du Foresto, S. Ridgway, “FLUOR: A stellar interferometer using single-mode infrared fibers,” in Proceedings of ESO Meeting on High-Resolution Imaging by Interferometry II, J. M. Beckers, F. Merkle, eds. (European Southern Observatory, Garching bei München, 1991).

Durrance, S. T.

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

Golimowski, D. A.

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

Kulkarni, S. R.

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

Kuper, T. G.

J. B. Breckinridge, T. G. Kuper, R. V. Shack, “Space Telescope low-scattered-light camera: a model,” Opt. Eng. 23, 816–820 (1984).
[CrossRef]

Lagrange, A-M.

J-L. Beuzit, D. Mouillet, A-M. Lagrange, J. Paufique, “Stellar coronograph for the cone-on + adaptive optics system. I. Description and performances,” Astron. Astrophys. Suppl. Ser. (1997).
[CrossRef]

Léger, A.

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
[CrossRef]

Mariotti, J-M.

B. Mennesson, J-M. Mariotti, “Array configurations for a space infrared nulling interferometer dedicated to the search for Earthlike extrasolar planets,” Icarus 218 (1997).

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
[CrossRef]

Matthews, K.

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

Mennesson, B.

B. Mennesson, J-M. Mariotti, “Array configurations for a space infrared nulling interferometer dedicated to the search for Earthlike extrasolar planets,” Icarus 218 (1997).

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

Mouillet, D.

J-L. Beuzit, D. Mouillet, A-M. Lagrange, J. Paufique, “Stellar coronograph for the cone-on + adaptive optics system. I. Description and performances,” Astron. Astrophys. Suppl. Ser. (1997).
[CrossRef]

Nakajima, T.

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

Ollivier, M.

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

Oppenheimer, B. R.

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

Paufique, J.

J-L. Beuzit, D. Mouillet, A-M. Lagrange, J. Paufique, “Stellar coronograph for the cone-on + adaptive optics system. I. Description and performances,” Astron. Astrophys. Suppl. Ser. (1997).
[CrossRef]

Puget, J-L.

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
[CrossRef]

Ridgway, S.

V. Coudé du Foresto, S. Ridgway, “FLUOR: A stellar interferometer using single-mode infrared fibers,” in Proceedings of ESO Meeting on High-Resolution Imaging by Interferometry II, J. M. Beckers, F. Merkle, eds. (European Southern Observatory, Garching bei München, 1991).

Rouan, D.

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
[CrossRef]

Schneider, J.

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
[CrossRef]

Shack, R. V.

J. B. Breckinridge, T. G. Kuper, R. V. Shack, “Space Telescope low-scattered-light camera: a model,” Opt. Eng. 23, 816–820 (1984).
[CrossRef]

Shao, M.

M. Shao, M. M. Colavita, “Long-baseline optical and infrared stellar interferometry,” Ann. Rev. Astron. Astrophys. 30, 457–498 (1992).
[CrossRef]

Smith, B. A.

B. A. Smith, R. J. Terrile, “A circumstellar disk around Beta Pictoris,” Science 226, 1421–1424 (1984).
[CrossRef] [PubMed]

Terrile, R. J.

B. A. Smith, R. J. Terrile, “A circumstellar disk around Beta Pictoris,” Science 226, 1421–1424 (1984).
[CrossRef] [PubMed]

Woolf, N. J.

J. R. P. Angel, N. J. Woolf, “An imaging nulling interferometer to study extrasolar planets,” Astrophys. J. 475, 373–379 (1997).
[CrossRef]

Ann. Rev. Astron. Astrophys.

M. Shao, M. M. Colavita, “Long-baseline optical and infrared stellar interferometry,” Ann. Rev. Astron. Astrophys. 30, 457–498 (1992).
[CrossRef]

Astron. Astrophys. Suppl. Ser.

J-L. Beuzit, D. Mouillet, A-M. Lagrange, J. Paufique, “Stellar coronograph for the cone-on + adaptive optics system. I. Description and performances,” Astron. Astrophys. Suppl. Ser. (1997).
[CrossRef]

Astrophys. J.

J. R. P. Angel, N. J. Woolf, “An imaging nulling interferometer to study extrasolar planets,” Astrophys. J. 475, 373–379 (1997).
[CrossRef]

Icarus

A. Léger, J-M. Mariotti, B. Mennesson, M. Ollivier, J-L. Puget, D. Rouan, J. Schneider, “Could we search for primitive life on extrasolar planets in the near future?” Icarus 123, 249–255 (1996).
[CrossRef]

B. Mennesson, J-M. Mariotti, “Array configurations for a space infrared nulling interferometer dedicated to the search for Earthlike extrasolar planets,” Icarus 218 (1997).

Nature (London)

J. R. P. Angel, “Ground-based imaging of extrasolar planets using adaptive optics,” Nature (London) 368, 203–207 (1994).

R. N. Bracewell, “Detecting nonsolar planets by spinning IR interferometer,” Nature (London) 274, 780–781 (1978).

T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, S. T. Durrance, “Discovery of a cool brown dwarf,” Nature (London) 378, 463–465 (1996).

Opt. Eng.

J. B. Breckinridge, T. G. Kuper, R. V. Shack, “Space Telescope low-scattered-light camera: a model,” Opt. Eng. 23, 816–820 (1984).
[CrossRef]

Science

B. A. Smith, R. J. Terrile, “A circumstellar disk around Beta Pictoris,” Science 226, 1421–1424 (1984).
[CrossRef] [PubMed]

Space Sci. Rev.

A. Léger, J-L. Puget, J-M. Mariotti, D. Rouan, J. Schneider, “How to evidence primitive life on an exo-planet?—the Darwin project,” Space Sci. Rev. 74, 163–169 (1995).
[CrossRef]

Other

J. R. P. Angel, “Use of a 16 m telescope to detect Earthlike planets,” in The Next Generation Space Telescope, P. Bély, C. Burrows, G. Illingworth, eds. (Space Telescope Science Institute, Baltimore, Md., 1989), pp. 81–88.

V. Coudé du Foresto, “Integrated optics in astronomical interferometry,” in Very High Angular Resolution Imaging, IAU Symposium 158, J. G. Robertson, W. J. Tango, eds. (Kluwer Academic, Dordrecht, The Netherlands, 1993).

V. Coudé du Foresto, S. Ridgway, “FLUOR: A stellar interferometer using single-mode infrared fibers,” in Proceedings of ESO Meeting on High-Resolution Imaging by Interferometry II, J. M. Beckers, F. Merkle, eds. (European Southern Observatory, Garching bei München, 1991).

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Figures (6)

Fig. 1
Fig. 1

Possible two-telescope setup for realizing spatial filtering. The wave front is sampled by the telescopes (T1, T2). The spatial filtering operation is performed on the focal plane of each telescope by the spatial filtering device (SFD). (The Airy disk is selected by a mask or a piece of single-mode optical fiber.) The clean beams are then recombined on a beam splitter (BS). The delay lines (DL) allow for compensation of the optical path difference.

Fig. 2
Fig. 2

Spectrum of the polishing defects (phase defects) applied to the ideal pupil. The high-frequency part (0.1 cm-1 < frequency < 1 cm-1) is a power law according to the HST mirror map. The low-frequency part (0.01 cm-1 < frequency < 0.1 cm-1) was considered linear to simulate roughly active optics corrections (no shape defects at the mirror scales, but major defects for frequencies corresponding to the distance between actuators.)

Fig. 3
Fig. 3

Representation of the wave front before spatial filtering: (a) amplitude, pupil with 1% dust, two large-scale coating defects (each of 1% amplitude); (b) phase, pupil with a λ/200 rms polishing defects and a λ/200 pointing defect.

Fig. 4
Fig. 4

Intensity in the subtractive recombination pattern of two defected pupils (λ/200 rms polishing defects and 1% dust) (a) without spatial filtering and (b) with spatial filtering. Note that the scale has been amplified by 105. The total energy spread in the black fringe is mainly due to the wave-front asymmetry caused by defects on optical components. In this case, the bright speckles in the recombination pattern are due to the hole in the wave front caused by dust.

Fig. 5
Fig. 5

Influence of (a) dust defects, (b) coating defects (one defect by pupil), (c) polishing defects, and (d) pointing errors on the rejection rate (dots, without spatial filtering; plusses, with spatial filtering). Defects that are best corrected are small in scale, such as dust and high-frequency polishing defects. Large-scale defects, particulary pointing errors, are not well corrected.

Fig. 6
Fig. 6

Influence of the size of the filtering hole on (a) the transmitted energy and (b) the rejection rate in the case of λ/100 rms phase defects. The best balance between the rejection rate and the number of photons collected in the case of a space mission dedicated to extrasolar planet detection and analysis appears to be reached when the filtering device has the size of the Airy disk. Even with the beam intensity perfectly adjusted, the loss of photons is still 25%.

Equations (3)

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ρ=Imax/Imin,
V=Imax-IminImax+Imin=ρ-1ρ+1.
T=t expjϕ.

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