Station/Shuttle Steers Clear Of Debris
By Frank Morring, Jr. 
JOHNSON SPACE CENTER, Houston - Shuttle commander Lee Archambault used the thrusters on the space shuttle Discovery to maneuver the International Space Station 180 degrees from its normal attitude when an orbiter is docked to it March 22, adding drag to the two big spacecraft to lower their orbit out of the way of a threatening piece of Chinese space debris passing by March 23.
Archambault left the shuttle/station stack in the attitude normally used for docking and undocking, with the orbiter forward instead of bringing up the rear in orbit. The tenuous atmosphere at the station altitude supplied enough drag to slow the two spacecraft by about 1 foot per second over the three hours it took to complete two orbits.
The maneuver, which started at 4:01 p.m. EDT March 22, lowered the orbit enough to get the station and shuttle out of the way of a 4-inch piece of an old Chinese rocket body that would have otherwise passed too close to the docked spacecraft for comfort March 23. The projected conjunction is particularly worrisome because astronauts Joe Acaba and Richard Arnold are scheduled to go outside March 23 for the third and final spacewalk of the STS-119/15A station assembly mission.
Mission managers believe that by letting nature take its course in lowering the orbit, the Chinese debris - left over from a 1999 launch - won't pose a danger to the spacecraft or the spacewalkers.
Meanwhile, inside the ISS Expedition 18 Commander Mike Fincke worked all day March 22 to test the new urine distillation assembly Discovery took into orbit to replace a unit that failed soon after it was installed last November. The unit worked well during a dry run March 21, but on March 22 Fincke and his crewmates had trouble filling it with urine stored in the Russian section of the station.
After consultations with station controllers here at Johnson Space Center, Fincke replaced the filter in the water recycling unit that includes the circular distiller, which must rotate to function in microgravity.
Meanwhile, Acaba and fellow astronaut Steve Swanson performed a six-and-a-half-hour spacewalk March 21 that accomplished most - but not all - of its objectives. The pair were able to loosen bolts and attach foot restraints to lay the groundwork for later replacement of the oldest batteries on the station. They also installed a GPS antenna on top of the Japanese Kibo module to guide the H-II Transfer Vehicle in to rendezvous on its first flight in September.
But a balky metal pin stymied plans to install a cargo attach point on the main station truss, so they had to stop before the job was finished and tie down the component with a tether. The mishap apparently resulted when one of the spacewalkers installed the pin incorrectly.
International Space Station photo: NASA TV
