Overnight, space shuttle Discovery has been steadily catching up to the International Space Station (ISS) and will be making its final docking with the orbiting laboratory at 1:16 p.m. CST.
Discovery's crew was awakened to begin preparations for the rendezvous at 5:53 a.m. The day's wake up song was "Woody's Roundup," performed by Riders in the Sky, played for mission specialist Alvin Drew, who's on his second trip to the space station.
"That music is pretty appropriate [for] today in that we are having our own roundup at the space station with about as many different visiting vehicles as you can imagine and getting together with our crewmates aboard the space station today," radioed Drew. "So, we're looking forward to our own roundup going well today."
The terminal initiation burn, an engine firing that will give Discovery one last big push toward the station, is scheduled to take place at 10:33 a.m. That should bring Discovery to a point 600 feet below the station at 12:15 p.m., at which point commander Steve Lindsey will fly the shuttle through a back flip, or Rendezvous Pitch Maneuver.
As he does so, station flight engineers Paolo Nespoli and Cady Coleman will be positioned at the windows of the Zvezda module, armed with 800- and 400 millimeter lens cameras to photograph Discovery's heat shield. The photos will be sent down to specialists on the ground for analysis.
Following the flip, Lindsey will fly Discovery to a point 310 feet directly in front of the station, and then allow the ISS to catch up with the shuttle for docking. After a series of leak checks, the two crews should be able to open the hatches between them at 3:18 p.m.
Following a welcome ceremony and safety briefing for the space station's six new visitors, Discovery's crew will get to work transferring the cargo they are delivering. Drew, pilot Eric Boe and mission specialists Michael Barratt and Nicole Stott will use the shuttle's and station's robotic arms to remove the ExPRESS Logistics Carrier 4 from Discovery's payload bay and install it on the starboard side of the station's truss system. There it will be used to store spare parts, including a spare radiator that launched with it.
Tim Kopra, who was replaced by Steve Bowen on Discovery's crew after being injured in a bike accident last month, told his former crewmates on Friday that he felt he was with them "in spirit."
To that, mission specialist Michael Barratt replied, "I have to tell you that you are here in a little bit more than spirit but we will have to explain that when we get back."
Photographs taken by the crew on-orbit and released by NASA may have revealed what Barratt meant.
The photos capture what looks to be a cardboard cutout of an astronaut on board Discovery's middeck. The "flat" astronaut's head is obscured by floating equipment but in one of the photos, Kopra's name can just about be read on his name tag.
Flat Stanley Timothy in space. Click on image to see full frame. Credit: NASA
At 10:33 a.m. CST, Discovery performed an 11-second burn using its left orbital maneuvering system engine. Called the terminal initiation burn, the firing increased the shuttle's rate of approach to the space station by 5.7 miles per hour (8.4 feet per second).
The burn, which occurred when the shuttle was about nine miles from the space station, sets up Discovery's rendezvous with the orbiting lab in the next orbit and a half, supporting a docking time of 1:16 p.m. CST.
With space shuttle Discovery at a distance of about 600 feet below the International Space Station, STS-133 commander Steven Lindsey began the rendezvous pitch maneuver (RPM) at 12:15 p.m. CST, a slow "back flip" enabling the space station's crew to photograph the orbiter's thermal protection system through the windows of the Zvezda service module.
Using cameras with 800mm and 400mm lenses respectively, Expedition 26 flight engineers Paolo Nespoli and Cady Coleman captured photos of Discovery's upper and lower surfaces. Their photos will be transmitted to Mission Control in Houston for evaluation to determine whether the heat shield sustained any damage during launch.
Credit: NASA TV
As this is Discovery's final flight, this was also its last orbital back flip, a maneuver it was first to perform during the 2005 STS-114 mission. The RPM was added as one of the safety enhancements following the loss of space shuttle Columbia eight years ago this month.
With commander Steven Lindsey at its controls, space shuttle Discovery docked for its last time with the International Space Station at 1:14 p.m. CST on Saturday as the two spacecraft orbited 220 miles over western Australia.
"Station and Houston, Discovery has capture confirmed," said Eric Boe, STS-133 pilot.
Discovery docked to the International Space Station. Credit: NASA TV
UPDATE: A hard mate between Discovery and the ISS was delayed until 2:04 p.m. as the relative motion between the two vehicles dampened out. The station mass, now about 1.2 million pounds, with docked spacecraft, modules and robotic components from all international partners attached at the same time, contributed to an alignment issue between the shuttle and station docking rings. The hard mate between Discovery and station could not be achieved until the motion stopped and the shuttle's docking ring could be retracted.
The 35th visit by a shuttle to the ISS, Discovery's arrival begins at least a week of joint mission operations between the STS-133 and Expedition 26 crew members. It is expected to take about two hours for the hatches between the spacecraft to be opened.
Station commander Scott Kelly and flight engineers Paolo Nespoli, Cady Coleman, Alexander Kaleri, Dmitry Kondratyev and Oleg Skripochka will welcome the shuttle crew onboard and brief them on safety procedures before beginning their first activities together.
This is space shuttle Discovery's 13th and final arrival at the International Space Station. It's first docking back on May 29, 1999 was also the first time a space shuttle joined with the then-burgeoning orbital laboratory.
The view from Discovery's docking ring during approach. Credit: NASA TV
The hatches between Discovery and the International Space Station were opened at 3:16 p.m. CST, beginning at least a week of joint ops between the six STS-133 astronauts and the six ISS Expedition 26 crewmates.
Discovery's crew enters the International Space Station. Credit: NASA TV
Following a safety briefing, the 12 members of the joint crew set to work on their first tasks. Using the station's Canadarm2 robotic arm, they will move the ExPRESS Logistics Carrier-4 (ELC4) from Discovery's payload bay and attach it to the starboard side of the station's truss. There it will be used to store spare parts, including a spare radiator that was launched with it.
Crew members will also bring spacesuits and spacewalk equipment over from the shuttle's middeck to the station's Quest airlock to begin setting up for the mission's first spacewalk on Monday.
Discovery's crew stayed up late to finish attaching a spare parts pallet to the International Space Station's backbone truss.
"Looking at the timeline, we're running about an hour late this evening," radioed Mission Control in Houston to both STS-133 commander Steven Lindsey and the station's commander Scott Kelly. "Our preference down here though, would be to go ahead and press through ELC4 install. That would get you to bed a little late, but we would be able to let you sleep in 30 minutes longer in the morning."
Both commanders agreed with pressing ahead.
ExPRESS Logistics Carrier-4 (ELC4) attached to the station. Credit: NASA TV
Mission specialists Michael Barratt and Nicole Stott, using the station's robotic arm, plucked the ExPRESS Logistics Carrier-4 (ELC4) from the shuttle's payload bay and handed it off to the shuttle's arm, operated by mission specialist Alvin Drew and pilot Eric Boe.
After moving the base of the station's Canadarm2, Discovery's Canadarm handed ELC4 back for installation on the Earth-facing, starboard side of the station's S3 truss lower inboard passive attachment system (PAS).
Barratt and Stott controlled the station arm's movements from inside the Earth-facing, multi-windowed Cupola, prompting Mission Control to ask if they felt more like a bat hanging upside down or gopher popping upside.
"I think we are kind of a bat-pher," replied Barratt. "I guess we are kind of hanging upside down and enjoying the dark, and a gopher in that... well, a groundhog maybe -- if we could do this again every day, it would be fine."