[meteorite-list] Deep Impact Feared Lost

[Ron Baalke]

http://www.spaceflightnow.com/news/n1309/10deepimpact/ 
 
NASA's plucky Deep Impact probe feared lost
BY STEPHEN CLARK
SPACEFLIGHT NOW
September 10, 2013

Scientists fear NASA's comet-chasing Deep Impact spacecraft may be lost 
in space after a software glitch cut off communications between the aging 
space probe and befuddled engineers on Earth.
 
NASA last heard from the distant spacecraft on Aug. 8, and efforts to 
restore contact with Deep Impact have produced no results. Engineers will 
continue to uplink commands to the probe in an attempt to reestablish 
communications, the agency said in a press release Tuesday.

Officials blame Deep Impact's problem on a software glitch, according 
to Michael A'Hearn, the mission's principal investigator from the University 
of Maryland in College Park.

"The problem was a software issue in having run the mission for many years 
past its design lifetime," A'Hearn told Spaceflight Now. "This basically 
caused an overflow in the on-board time, which in turn caused a continuous 
cycle of rebooting the on-board computer."

About the size of a sports utility vehicle, the Deep Impact spacecraft 
launched in January 2005 and reached comet Tempel 1 less than six months 
later, deploying a copper impactor to slam into the comet's nucleus as 
the Deep Impact mothership and telescopes studied material ejected from 
the cosmic collision.

Mission controllers reshaped Deep Impact's course several times after 
its primary mission ended, beginning an extended phase named EPOXI. placing 
the probe on course to fly by comet Hartley 2 in November 2010. Since 
the Hartley 2 encounter, Deep Impact used its high-resolution telescope 
to make long-range observations of comets Garradd (C/2009 P1) and ISON.

A'Hearn posted a status update Sept. 3 on the mission's website announcing 
the spacecraft's trouble, which occurred during Deep Impact's comet ISON 
observing campaign. Deep Impact was storing data on ISON on-board the 
spacecraft before beaming it back to Earth, A'Hearn said, so none of the 
information has been recovered.

"The challenge is to understand the present state of the spacecraft and 
how to communicate with it, a problem that the spacecraft team is studying 
very hard," A'Hearn said.

In a story posted Sept. 5 on the Nature News blog, A'Hearn said engineers 
are racing the clock because the probe could lose electrical power if 
its solar panels are pointed away from the sun.

A'Hearn told Spaceflight Now on Tuesday engineers are not sure which way 
Deep Impact is pointing or if it is spinning out of control.

"Since we don't have communication, we don't know whether it is tumbling 
or not. It is correct that we don't have control, so it might be," A'Hearn 
told Spaceflight Now.

Deep Impact has a steerable high-gain antenna, which requires precise 
pointing toward Earth to connect with controllers. Two less capable 
omnidirectional low-gain antennas are also aboard Deep Impact.

Built by Ball Aerospace and Technologies Corp., the Deep Impact spacecraft 
was intended for a brief six-month primary mission. Since its launch 
eight-and-a-half years ago, the probe has traveled about 4.7 billion miles, 
according to NASA.

Deep Impact is running low on fuel, but NASA authorized a series of rocket 
burns in 2011 and 2012 to alter the craft's trajectory and set up a potential 
flyby of asteroid 2002 GT, a mystical object that regularly crosses paths 
with Earth. It could be a target for future human expeditions and it has 
a risk of one day colliding with Earth.

If Deep Impact makes it, the flyby with 2002 GT would occur in January 
2020.