[meteorite-list] Deep Impact Closes In On Comet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 28 18:37:28 2005
Message-ID: <200504282236.j3SMa9G12182_at_zagami.jpl.nasa.gov>

http://rockymountainnews.com/drmn/state/article/0,1299,DRMN_21_3734569,00.html

Boulder spacecraft closes in on comet
By Jim Erickson
Rocky Mountain News (Colorado)
April 28, 2005

NASA's Boulder-built Deep Impact spacecraft has spied its target, Comet
Tempel 1, and is streaking toward a July 4 collision with the errant
iceball.

The spacecraft captured its first image of Tempel 1 on Monday, and the
space agency released it Wednesday.

The black-and-white picture was shot with the Deep Impact's
medium-resolution camera, from a distance of 39.7 million miles.

Meanwhile, engineers continue to troubleshoot a focusing problem with
Deep Impact's main camera/telescope - the High Resolution Instrument.

The $330 million Deep Impact is expected to blast an Invesco Field- size
crater in the side of Tempel 1 in a mission to probe the origins of the
solar system.

Scientists had hoped the High Resolution Instrument would reveal crater
details as small as 3 feet across, said H. Jay Melosh, a University of
Arizona planetary scientist.

But because of the focusing problem, it now appears its sharpest
pictures will have a resolution of about 6 feet, said Melosh, a member
of the Deep Impact science team.

"I would say it's a major concern. We're all very disappointed at the
performance of this imaging system," he said Wednesday.

Deep Impact was built by Ball Aerospace & Technologies of Boulder. A
Ball spokesman said Wednesday that NASA asked the company not to discuss
Deep Impact's blurry vision with reporters.

After the Jan. 12 Deep Impact launch, engineers noticed moisture trapped
inside the High Resolution Instrument, which is a telescope fitted with
a digital camera.

The moisture likely entered the instrument while it sat on the Florida
launch pad or during the spacecraft's ascent through Earth's
atmos-phere, the space agency said last month.

Engineers initially blamed the focusing problem on three supports that
cradle the telescope's 12-inch- diameter main mirror, Melosh said.

They suspected the supports absorbed some of the moisture and expanded,
moving the telescope's focal point 1.9 millimeters. A millimeter is
about the thickness of a paper-clip wire.

To correct the problem, heaters were used to "bake" moisture out of the
telescope. But baking didn't improve the focus.

The current plan: Use image-processing software to sharpen comet images
sent back by the High Resolution Instrument. A similar procedure was
used to fix the Hubble Space Telescope's blurry vision until that
observatory was fitted with corrective optics.
Received on Thu 28 Apr 2005 06:36:08 PM PDT