This artist's impression of the fly-by spacecraft releasing the impactor, 24 hours before the impact event. Pictured from left to right are Comet 9P/Tempel 1, the impactor and the fly-by spacecraft. The impactor is a 370-kilogram mass with an on-board guidance system. The fly-by spacecraft includes a solar panel (right), a high-gain antenna (top), a debris shield (left, background) and science instruments for high and medium resolution imaging, infrared spectroscopy and optical navigation (yellow box and cylinder, lower left).

The fly-by spacecraft is about 3.2 metres long, 1.7 metres wide and 2.3 metres high. The launch payload has a mass of 1020 kilograms.