Monitoring the Comet

Astronomers worldwide monitor Comet 9P/Tempel 1, in order to characterize it completely before the collision with the Deep Impact projectile, that will take place on July 4. This allows astronomers to have a good knowledge of the structure and behaviour of the comet, thereby ensuring one can distinguish the effects of the impact from the normal activity of the comet. For that purpose, images are obtained daily using medium size telescopes, while deeper images and spectra are taken once per month with larger telescopes.

To ensure that the daily monitoring is not affected by bad weather in a given observatory, a collaboration has been set up between the Deep Impact mission and the PLANET project.

The PLANET project uses telescopes at ESO/La Silla, at the Canopus observatory (Tasmania, Australia) and Boyden observatory (South Africa) in the search of extrasolar planets, using the microlensing method. To this aim, the PLANET collaboration monitors continuously dense star fields, trying to detect the effect of a planet surrounding an intervening lens star.

The PLANET collaboration's strategy of using three observatories is also ideal for the monitoring of comet Tempel 1: one can be almost certain that at least one of the 3 observatories will have good weather.

An example of images obtained by PLANET is available on the PLANET web site at

From May 31 to June 3, the ESO 3.5m New Technology Telescope observed the comet in the framework of the monthly monitoring. Many images and spectra were obtained. An example of such an image, as well as the way it was obtained, is shown in the From the Telescope to the Web page.