Discovery celebrates 25th birthday with station docking
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: August 30, 2009
Shuttle commander Frederick "C.J." Sturckow, forced by a leaky steering jet to use Discovery's big maneuvering thrusters instead of preferred fine-control vernier engines, deftly guided the spaceplane to a flawless docking with the International Space Station Sunday night to cap a two-day rendezvous.
Approaching from directly in front of the laboratory complex as both spacecraft sailed 220 miles above the central Atlantic Ocean at 5 miles per second, the shuttle's payload bay docking port engaged its counterpart on the front end of the statin's Harmony module at 8:54 p.m. EDT, about 10 minutes ahead of schedule.
"Station and Houston, from Discovery, capture confirmed," astronaut Patrick Forrester radioed from the shuttle.
Over the next 90-minute orbit, the docking mechanisms locked the two craft firmly together and leak checks were carried out to confirm a tight seal before hatch opening later in the evening.
"Hey Pat, before the hatches get opened there and we have a hard time finding C.J., the orbit one shift wanted to pass along what a great job he did on this first ever vern-failed docking," astronaut Chris Ferguson radioed from mission control. "Did a fantastic job. And you'll be happy to know it occurred on the 25th anniversary of the maiden flight of Discovery. So would you pass that along to him for us?"
"OK, Houston, we appreciate those words and thanks for the great support and the great calls by the ground today, a couple of key saves were made," replied Sturckow, believed to be the first astronaut to make four trips to the space station. "So thank you very much."
A few minutes later, at 10:33 p.m., hatches were opened and Sturckow, wearing a bright red Marine Corps baseball cap, led his crew into the space station.
"Space shuttle Discovery, arriving," station commander Gennady Padalka said, ringing the ship's bell in the Harmony module.
Padalka and his five station crewmates warmly embraced their seven shuttle colleagues before gathering for a safety briefing and getting down to work.
The primary goals of the mission are to deliver 7.5 tons of science equipment, life support gear and supplies. Nicole Stott, who hitched a ride to the station aboard Discovery, moved her Soyuz seat liner into the station shortly after docking and at 11:49 p.m., officially replaced astronaut Timothy Kopra as a member of the Expedition 20 crew. Kopra plans to return to Earth aboard the shuttle in Stott's place after 57 days in space.
Three spacewalks are planned, overnight Tuesday, Thursday and Saturday, to replace a 1,800-pound ammonia coolant system tank, to retrieve external experiments, deploy a spare parts mounting mechanism and to install wiring needed for a new module scheduled for launch next year.
Before Discovery's arrival, the 83-percent-complete space station massed 699,010 pounds. At docking, the combined spacecraft massed nearly a million pounds.
Discovery's approach to the space station was the first ever conducted using the shuttle's big primary reaction control system maneuvering thrusters, which generate 870 pounds of thrust when ignited. Shuttle commanders normally rely on six small 24-pound-thrust vernier jets - two in the nose and four in the shuttle's aft - to precisely control the final rendezvous sequence.
But one of Discovery's two forward vernier jets failed after launch overnight Friday, forcing flight controllers to close a manifold that isolated both forward thrusters. As a result, Sturckow had to complete the rendezvous using the larger primary jets instead.
Shuttle astronauts routinely train for dockings using an alternate digital autopilot mode, but Sturckow was the first to fly such a "no-vernier" approach in practice.
Trailing the station by 9.2 miles, Sturckow and Ford fired the shuttle's left orbital maneuvering system rocket at 6:26 p.m. to begin the final phase of the rendezvous.
At 8:03 p.m., with the shuttle positioned about 600 feet directly below the station, Sturckow used the primary jets to kick off a slow nine-minute back-flip maneuver to expose the shuttle's belly to the space station.
As it pitched around at a sedate three quarters of a degree per second, Padalka and Michael Barratt, using digital cameras equipped with 400-mm and 800-mm lenses, photographed the shuttle's heat shield to help engineers assess its health before re-entry.
After the flip maneuver, Sturckow flew Discovery in an arc up to a point about 400 feet directly in front of the station. From there, he manually guided the spaceplane in for docking.
"With the verniers, you have finer control with the smaller jets, you could tell he had to fly it a little bit different," said lead Flight Director Tony Ceccacci. "For one instance, it would add more closing rate in and he'd have to brake to make sure his closing rates weren't too high. In other situations, he had to add closing rate.
"So it was just a little bit more complicated as far as where he had to do these different tasks and such than he would if he had verniers. Again, the crew has trained this. Yesterday, we had a discussion with C.J., what the critical points were, and he just flew it like a champ today."