We revisit the nulling interferometer performances that are needed for direct detection and the spectroscopic analysis of exoplanets, e.g., with the DARWIN [European Space Agency-SCI 12 (2000)] or TPF-I [JPL Publ. 05-5, (2005)] missions. Two types of requirement are found, one concerning the mean value of the instrumental nulling function 〈nl(lambda)〉 and another regarding its stability. The stress is usually put on the former. It is stringent at short wavelengths but somewhat relaxed at longer wavelengths. The latter, which we call the variability noise condition, does not usually receive enough attention. It is required regardless of telescope size and stellar distance. The results from three nulling experiments performed in laboratories around the world are reported and compared with the requirements. All three exhibit 1/f noise that is incompatible with the performances required by the mission. As pointed out by Lay [Appl. Opt. 43, 6100-6123 (2004)], this stability problem is not fully solved by modulation techniques. Adequate solutions must be found that are likely to include servo systems using the stellar signal itself as a reference and internal metrology with high stability.
© 2006 Optical Society of America
Original Manuscript: February 9, 2005
Manuscript Accepted: May 16, 2005
Bruno Chazelas, Frank Brachet, Pascal Bordé, Bertrand Mennesson, Marc Ollivier, Olivier Absil, Alain Labèque, Claude Valette, and Alain Léger, "Instrumental stability requirements for exoplanet detection with a nulling interferometer: variability noise as a central issue," Appl. Opt. 45, 984-992 (2006)