Deep Impact

The washing-machine-sized, copper-fortified impactor is expected to make a good impression on the comet Tempel 1 at 0152 EDT July 4th. It was successfully released from the flyby spacecraft at 0207 EDT on Sunday.

At release, the impactor was about 547,000 miles away from its target. Six hours prior to impactor release, the Deep Impact spacecraft successfully performed its fourth trajectory correction maneuver.

Soon after the trajectory maneuver was completed, the impactor engineers began the final steps that would lead to it being ready for free flight. In order to release the impactor, separation pyros fired allowing a spring to uncoil and separate the two spacecraft at a speed of about 0.78 mile per hour.

With Tempel 1 approaching at about 6 miles per second, there is little time for mission controllers to admire their work.

The flyby craft began a 14-minute long divert burn to slow its velocity relative to the impactor by 227 miles per hour, keeping it out of the path of the onrushing comet nucleus and setting the stage for a ringside seat of celestial fireworks to come less than 24 hours later.

Deep Impact mission controllers have confirmed the impactor's S-band antenna is talking to the flyby spacecraft. All impactor data including the expected remarkable images of its final dive into the comet's nucleus will be transmitted to the flyby craft -- which will then downlink them to Deep Space Network antennas that are listening 134 million kilometers (83 million miles) away.

While all is going as expected on the Deep Impact spacecraft the comet itself is putting on something of a show. The 8.7-mile-long comet Tempel 1 displayed another cometary outburst on July 2 when a massive, short-lived blast of ice or other particles escaped from inside the comet's nucleus and temporarily expanded the size and reflectivity of the cloud of dust and gas (coma) that surrounds it. The July 2 outburst is the fourth observed in the past three weeks.

Three of the outbursts appear to have originated from the same area on the surface of the nucleus but they do not occur every time that that area faces the Sun.

"The comet is definitely full of surprises so far and probably has a few more in store for us," said Deep Impact Project Manager Rick Grammier of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "None of this overly concerns us nor has it forced us to modify our nominal mission plan."

FMI: www.nasa.gov/deepimpact