Many existing interferometers (e.g. SUSI, COAST, IOTA, VINCI) are not
phase stabilised. These interferometers measure observables which are
not affected by atmospheric phase changes, so that it is not necessary
to track the atmospheric phase fluctuations. The principle benefit of
this is that a bright reference star is not required as the
observables can be integrated over many fringe coherence
times. Example observables include the visibility amplitude and the
bispectrum or ``triple-produce'' (the phase of the bispectrum known as
the closure phase is more often discussed, but the bispectrum is the
fundamental observable).
Robert Tubbs
平成16年11月18日
