Volume: 03, Issue: 07 04/06/2005 
Artist conception of Deep Impact collision. Image courtesy NASA/JPL.
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Other Articles in This Issue:
Space Shuttle Discovery Moves to Launch Pad
Spirit and Opportunity Head for Triple Overtime
Northern Lights and Southern Lights Are Not Mirror Images
Enhance Your Teaching Skills Online

Deep Impact Cruises toward Comet

NASA’s Deep Impact spacecraft is now one step closer to its planned collision with comet Tempel 1 on July 4, 2005. The spacecraft has completed the commissioning phase of the mission and has moved into the cruise phase, which will continue until about 60 days before the encounter with the comet.

Soon after launch on Jan. 12, 2005, Deep Impact entered the commissioning phase, one of the spacecraft’s five mission phases. During that phase, the mission team made sure the craft and its instruments were healthy and fully functional.

The spacecraft's autonomous navigation system was activated and tested using the Moon and Jupiter as targets. Deep Impact’s high gain antenna, which will relay images and data of the cometary collision, was activated and is operating properly. In addition, a trajectory correction maneuver refining the flight path to Tempel 1 was so successful that a second one planned for March 31 has been cancelled.

Another event during commissioning phase was the bake-out heating of the spacecraft's High Resolution Instrument to remove normal residual moisture from its barrel. The moisture was a result of absorption into the structure of the instrument during the vehicle's last hours on the launch pad and its transit through the atmosphere to space.

At completion of the bake-out procedure, test images were taken through the High Resolution Instrument. These images indicate the telescope has not reached perfect focus. A special team has been formed to investigate the performance and to evaluate activities to bring the telescope the rest of the way to focus. Future calibration tests will provide additional information about the instrument’s performance.

The Deep Impact spacecraft has four data collectors to observe the effects of the cometary collision: a camera and infrared spectrometer comprise the High Resolution Instrument; a Medium Resolution Instrument; and a duplicate camera on the Impactor Targeting Sensor. They will record the vehicle's final moments before it is run over by comet Tempel 1 at approximately 23,000 miles per hour. The Medium Resolution Instrument and Impactor Targeting Sensor are performing as expected.

"We are very early in the process of examining the data from all the instruments,” explained Dr. Michael A'Hearn of the University of Maryland. “It appears our infrared spectrometer is performing spectacularly, and even if the spatial resolution of the High Resolution Instrument remains at present levels, we still expect to obtain the best, most detailed pictures of a comet ever taken."

Added Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion Laboratory, "This in no way will affect our ability to impact the comet on July 4. Everyone on the science and engineering teams is getting very excited and looking forward to the encounter."

Deep Impact is comprised of two parts, a flyby spacecraft and a smaller impactor. The impactor will be released into the comet's path for the planned high-speed collision. The crater produced by the impactor is expected to range from the width of a house up to the size of a football stadium and be from two to 14 stories deep. Ice and dust debris will be ejected from the crater, revealing the material beneath.

Along with the imagers aboard Deep Impact, NASA's Hubble, Spitzer, and Chandra space telescopes, along with the largest telescopes on Earth, will observe the effects of the material flying from the comet's newly formed crater.

An intimate glimpse beneath the surface of a comet, where material and debris from the formation of the solar system remain relatively unchanged, will answer basic questions about how the solar system formed. The effects of the collision will offer a better look at the nature and composition of these celestial travelers.

Deep Impact is a mission in NASA's Discovery Program of moderately priced solar system exploration missions. For more information about Deep Impact on the Internet, visit http://www.nasa.gov/deepimpact .

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