The light curve of the comet 9P/Tempel 1: Temporal evolution from 1867 till 2005

The light curves of the periodic comet 9P/Tempel 1 obtained during its apparitions in 1972, 1983, 1994, and 2005 have been constructed and studied. The values of the photometric parameters H 0 , n , and H 10 have been determined for these apparitions; and secular variations of the comet’s brightness have been studied. The light curve of the comet obtained close to the moment of the artificial impact agrees well with the change in the production rate of water molecules. The presented results are important from the point of the possible change in the photometric parameters induced by the artificial impact and the long-term evolution of the cometary core activity.