[meteorite-list] Deep Impact May Never Glimpse Comet Crater

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Jul 18 21:13:51 2005
Message-ID: <200507190113.j6J1D2R18028_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn7688--deep-impact-may-never-glimpse-comet-crater.html

Deep Impact may never glimpse comet crater
Stuart Clark
New Scientist
18 July 2005

NASA's Deep Impact may fail to live up to its billing as the first
mission to look inside a comet. Computer processing designed to correct
the spacecraft's defocused camera cannot fully correct the images taken
just after impact. If the situation cannot be rectified, there will be
no way of seeing the newly formed crater - one of the mission's major goals.

Deep Impact sent a 370-kilogram projectile into comet Tempel 1 on 4
July. Scientists had hoped to use the flyby spacecraft to see the bottom
of the resulting crater in order to glimpse the comet's interior
composition. They also wanted to see the crater's sides to look for
layering, rather like the geological strata on Earth. Several groups had
even placed bets on the crater's size, with estimates ranging from 10 to
250 metres. Now, the prize fund could go unclaimed.

The problem lies in the High Resolution Instrument (HRI) on the flyby
spacecraft. In March, mission managers discovered it was out of focus.
The fuzzy images were blamed on moisture settling in the camera during
the spacecraft's final few hours on the launch pad and during its flight
through the Earth's atmosphere. Scientists tried to bake-out the
moisture. But when that failed to fix the problem, they turned instead
to image-processing techniques, which they felt could restore the images.
          
Dust mask

Unfortunately, the techniques only work on high-contrast images. And
when the impactor struck Tempel 1 at more than 10 km per second, it
raised more dust than anyone expected. This masked the surface features,
rendering them too faint for computer processing to reliably correct.

But scientists are still in contact with the spacecraft and are
re-calibrating HRI, says Deep Impact's principal investigator, Michael
A'Hearn at the University of Maryland in College Park, US. Despite the
probe now being far out of reach of the comet, NASA can use the new
calibration data to reprocess the impact images. "We still hope to see
the crater," A'Hearn told New Scientist.

Even if the crater images are lost, A'Hearn believes the mission was a
great success. "Our view is that we went to a new place and have done
exciting new science, just perhaps not as much as we had hoped," he says.

Andrew Coates, an astrophysicist at Mullard Space Science Laboratory at
University College London, agrees: "This is not a failure. We scored a
direct hit on a comet and have a lot of interesting data."
Received on Mon 18 Jul 2005 09:13:01 PM PDT