Published online by Cambridge University Press: 12 April 2016
The HIPPARCOS Input Catalogue comprises about 118,000 entries of which 16,000 are flagged as related to double or multiple stars. Data analysis begins by fitting Fourier model signals to the observations: the intensity coefficients and the phases at several locations on the spatial modulator are estimated and a first rough recognition of possibly unknown non-single stars is performed. After calibration corrections, a normal point is produced at every transit of a star across the field of view of the telescope and the improved parameters are stored for extensive multiplicity testing and relative astrometry when enough scans are accumulated.