This story was updated at 8:04 p.m.
EDT
HOUSTON - NASA on Wednesday tracked
a piece of space junk leftover from a Chinese anti-satellite test in 2007 that
zoomed past the shuttle Atlantis and the attached Hubble Space Telescope, which
astronauts plucked from orbit earlier in the day.
The satellite
debris flew about 1.7 miles (2.8 km) ahead and a bit below Atlantis at its
closest approach, but it was well clear of the shuttle and did not require the
astronaut crew to move the spacecraft.
"No action was required for the
crew," said NASA commentator Pat Ryan on NASA TV.
Ryan said the piece of debris was
small, about 4 inches (10 cm) in size. It buzzed by Atlantis at about 7:28 p.m.
EDT (2328 GMT). In addition to flying in front of Atlantis, the space junk was
about 492 feet (150 meters) below and just over 2.4 miles (4 km) outside the
shuttle's orbital plane, Ryan said.
Atlantis and Hubble are currently
flying about 350 miles (653 km) above Earth in an orbit that has a
higher risk of space debris hits, in part because of the Chinese
anti-satellite test, in which China intentionally destroyed the weather
satellite Fengyun
1C in 2007.
An accidental
crash between a Russian and U.S. satellite that occurred on Feb. 10 as both
were flying 490 miles (790 km) above Siberia also contributed to the extra
risk, NASA officials have said.
NASA typically moves spacecraft
clear of space junk that wanders too near a shuttle or the International Space
Station when the debris passes within a box-like boundary around the crewed
vehicle. The Chinese debris was in NASA's "yellow" category, meaning a maneuver
to dodge would be unlikely, agency officials said in a statement.
Space junk risk
The risk of a piece of space junk
seriously damaging Atlantis is about a 1-in-229 chance in its current orbit.
That is higher than the typical 1-in-300 chance of major hits for shuttles
headed to the International Space Station, which flies in a lower 220-mile
(354-km) orbit, but is within NASA's flight rule limits, the agency has said.
LeRoy Cain, NASA's deputy shuttle
program manager, told reporters Wednesday that NASA and the Department of
Defense's U.S. Space Surveillance Network are tracking the debris environment
around Atlantis and Hubble much the same as they would for any manned
spaceflight.
"We're not doing anything
different," Cain said in a briefing here at NASA's Johnson Space Center. "The
process is a good one. It's tried and true."
In the extremely remote chance that
the Atlantis suffers a serious strike and cannot return to Earth, NASA has also
primed the shuttle Endeavour to launch a rescue
mission to retrieve the stranded astronauts.
Healthy heat shield
The Atlantis astronauts are flying
an 11-day mission to Hubble to perform NASA's fifth and final service call on
the aging
space telescope. Earlier Wednesday, they used the shuttle's robotic arm to
grab Hubble and secure it in their cargo bay so it can be upgraded and
repaired.
On Thursday, they will begin the
first of five back-to-back spacewalks to install two new cameras, attempt
unprecedented repairs on two other instruments and perform some much-needed
maintenance.
Cain said today that Atlantis' heat
shield appears to be in fine shape based on the analysis of a detailed
inspection performed by the shuttle crew yesterday. An impact sensor on one of
the heat-resistant panels lining the shuttle's starboard wing did detect an
apparent debris strike within the last 24 hours, but the hit was too weak to
cause any serious damage, Cain said.
Mission Control radioed the Atlantis
astronauts late Wednesday to say that no focused inspection of their heat
shield with a sensor-tipped boom will be required tomorrow. A trail of minor dings to some starboard side tiles were already deemed to pose no health concern for Atlantis, NASA said.
"That's excellent news," Atlantis
skipper Scott Altman said. "We appreciate that."
Flight controllers did ask the
astronauts to pencil in some time on Friday for a quick robotic arm scan of 16
heat-resistant tiles near the shuttle's nose. The tiles were inadvertently
skipped during an inspection earlier this week.
NASA has kept a close eye on the
integrity of its shuttle heat shields during flight since 2003, when a piece of
launch debris damaged the shuttle Columbia's heat shield, ultimately leading to
its destruction and the deaths of seven astronauts during re-entry.
SPACE.com is providing continuous
coverage of NASA's last mission to the Hubble Space Telescope with senior
editor Tariq Malik in Houston and reporter Clara Moskowitz in New York. Click here for mission
updates and SPACE.com's live NASA TV video feed.
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