4.6 Conclusion

I have presented some elements of the present state of the art in optical interferometry focusing on the functional description, some design choices and the various limitations with the objective to give to the readers the keys to compare this technique with radio interferometry at millimeter wavelengths.

We see that optical interferometry is a younger technique than the radio interferometry because of the complexity of the systems mainly due to the struggle against the atmosphere. It leads to smaller spatial resolution but has still to learn from the radio experience.

We are entering a new era where optical interferometers with large telescopes and increased sensitivity become general user instruments (KI, VLTI). I did not address the topic of optical interferometry in space that faces other challenges. However the search for extra-solar terrestrial planets is certainly driving this area with two main projects: the Space Interferometry Mission (SIM) dedicated to astrometry and the TPF/DARWIN mission focused on nulling interferometry.

Note: To obtain exhaustive and todate information on optical interferometers, I advise the reader to browse OLBIN, the optical long baseline interferometry newsletter managed by P. Lawson. The address is http://olbin.jpl.nasa.gov.

Figure credits

Fig. 4.1:

L. Rarogiewicz, Mount Wilson Observatory.

Fig. 4.2:

Département Fresnel, Observatoire de la Côte d'Azur; Smithsonian Astrophysical Observatory and Harvard University Center for Astrophysics, University of Massachusetts; Georgia State University; European Southern Observatory.

Fig. 4.3:

Mullard Radio Astronomy Observatory, University of Cambridge; Jet Propulsion Laboratory, Palomar Observatory; European Southern Observatory.

Fig. 4.4:

Mullard Radio Astronomy Observatory, University of Cambridge; US Naval Observatory, Naval Research Laboratory, Lowell Observatory; Laboratoire d'Astrophysique, Observatoire de Grenoble.

Fig. 4.5:

European Southern Observatory.

Fig. 4.7:

European Southern Observatory [Mariotti et al. 1992].

Fig. 4.10:

right panel, Infrared Interferometry Group, Max-Planck Institut für Radioastronomie.

Fig. 4.11:

right figure, Laboratoire d'Astrophysique, Observatoire de Grenoble.

Fig. 4.13:

Annual review of astronomy and astrophysics [Labeyrie 1978]; Laboratoire d'Astrophysique, Observatoire de Grenoble.

Fig. 4.14:

AMBER consortium OCA, LAOG, UNSA, MPIfR, OAA (AMB-OSM-007 report).

Fig. 4.16:

Astronomy & Astrophysics Supplement Series, EDP Sciences [Coudé Du Foresto, Ridgway, & Mariotti 1997]; DESPA, Observatoire de Paris-Meudon.

Fig. 4.17:

AMBER consortium OCA, LAOG, UNSA, MPIfR, OAA (Instrument Analysis PDR Report).

Internet resources

The following web sites have been used for some figures of this chapter.

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Mount Wilson Observatory, 20ft interferometer (Fig. 4.1)

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GI2T (Fig. 4.2)

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IOTA (Fig. 4.2)

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CHARA (Fig. 4.2)

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VLTI (Figs. 4.2, 4.3, 4.5)

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COAST (Figs. 4.3, 4.4)

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PTI (Fig. 4.3)

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NPOI (Fig. 4.4)

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IONIC (Figs. 4.4, 4.13)

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MPIfR (Fig. 4.10)

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AMBER (Figs. 4.14, 4.17)

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FLUOR (Fig. 4.16)