Space Forum / Shuttle / March 2007

Space station sinks to new low - but it's OK

NASA says that's part of its plan for finishing the orbital outpost

http://www.msnbc.msn.com/id/17630218/

By James Oberg, NBC News space analyst // Special to MSNBC

  HOUSTON - The international space station has been literally falling out
of the

sky, according to NASA tracking data obtained by MSNBC.com. Under the
inexorable

decay of air drag, its orbital path around Earth has slipped down to 207
miles

(332 kilometers), the lowest average altitude in the nine-year life of the
project.

  A small rocket engine on a docked cargo ship is being fired this week to
boost

the orbit by a small amount. But since the orbit is continually dropping at

about 300 feet (90 meters) per day, the boost will be eaten up by the
effects of

air drag within several weeks.

  A graph released by NASA shows that the gradual decline began in earnest
after

the loss of shuttle Columbia in early 2003. Prior to that disaster, the
altitude

had been maintained at a fairly high level, thanks mainly to reboosts from

visiting shuttles. Since that event, all reboosts have been the
responsibility

of Russian spacecraft.

  However alarming the line on the graph might appear to be, NASA orbital

trajectory experts insist that the station's orbit is under control. They
say

the decline is part of a long-range plan for the current phase of orbital

assembly that involves particularly heavy payloads for shuttle missions.

They say the orbit is still stable, and scheduled Russian reboost rocket
firings

will not allow it to decay any further. And beginning late next year, when
the

delivery of the station's heaviest structural elements will be completed,
the

orbit will be reboosted to greater and greater altitudes.