Wavelength diversity uses multi-wavelength data to simultaneously estimate the point spread function (PSF)
of an imaging system and the astronomical object of interest e.g. a binary star with a faint companion. The
algorithm presented does not recover the PSFs directly but estimates the Zernike coefficients of the residual
wavefront phase aberration in the pupil of the telescope. For dual, and triple, channel point source imaging, the
common wavefront is estimated and the residuals between the measured and estimated PSFs correspond to non
common path aberrations in each of the imaging paths.
We propose a new post-processing technique for the detection of faint companions and the estimation of
their parameters from adaptive optics (AO) observations. We apply the optimal linear detector, which is the
Hotelling observer, to perform detection, astrometry and photometry on real and simulated data. The real
data was obtained from the AO system on the 3m Lick telescope<sup>1</sup>.
The Hotelling detector, which is a prewhitening matched filter, calculates the Hotelling test statistic which
is then compared to a threshold. If the test statistic is greater than the threshold the algorithm decides that a
companion is present. This decision is the main task performed by the Hotelling observer. After a detection is
made the location and intensity of the companion which maximise this test statistic are taken as the estimated
We compare the Hotelling approach with current detection algorithms widely used in astronomy. We discuss
the use of the estimation receiver operating characteristic (EROC) curve in quantifying the performance of the
algorithm with no prior estimate of the companion's location or intensity. The robustness of this technique to
errors in point spread function (PSF) estimation is also investigated.