Deep Impact at ESO
... The Deep Impact Mission
The NASA Deep Impact spacecraft started its six-month, one way, 431 million kilometre journey towards Comet 9P/Tempel 1 on January 12, 2005 from cape Canaveral on board a Delta II rocket. Once in the close vicinity of the comet, the spacecraft will launch a 1 by 1 metre probe that will hit the comet at about 37,000 kph (10,2 km/s), probably excavating a 100-m large crater. The impactor weighs 372 kg (of which 8 kg of fuel), with 113 kilograms of that being copper-made "cratering mass" - dead weight designed to help the impactor make a substantial crater in the cometary nucleus.
After releasing the impactor, the flyby spacecraft will execute a deflection manoeuvre so that it does not also collide with the comet; the manoeuvre will also slow it down enough to make observations after the impact and before flying past the nucleus. The 3.3x1.7x2.3 m, 515 kg, spacecraft will be watching the 6 km wide nucleus before, during and after the impact.
The kinetic energy released by the collision event will be 19 gigajoules, about the equivalent of the amount of energy released by exploding 4.5 tons of TNT.
By creating a crater and releasing dust and gas, Deep Impact will provide a glimpse beneath the surface of a comet, where material and debris from the solar system's formation remain relatively unchanged. Data returned from the Deep Impact spacecraft could provide opportunities for significant breakthroughs in our knowledge of how the solar system formed, the makeup of cometary interiors, and the role that cometary impacts may have played with Earth's early history and the beginning of life.
Although dramatic images of the impact may be sent to Earth in near-real time by the Deep Impact spacecraft and its impactor, the spacecraft themselves have limited remote sensing instrumentation. The parent spacecraft will observe the impact from 500 kilometres distance, and then briefly look at the other side of the nucleus, but most of the observations of the event will be carried out by other spacecraft and from Earth. You can read here more about the ambitious observing programme with ESO telescopes.
University of Maryland astronomy professor Dr. Michael A'Hearn is the Deep Impact principal investigator. The mission is managed by the Jet Propulsion Laboratory (JPL) for the Science Mission Directorate at NASA Headquarters. The Deep Impact web site is at http://www.nasa.gov/deepimpact. Additional information is available at the Deep Impact project homepage at deepimpact.jpl.nasa.gov.
This text is partially based on information extracted from the NASA Deep Impact Launch Press Kit.