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
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
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."