A Russian Soyuz spacecraft carrying two rookie cosmonauts and a NASA shuttle veteran bound for the International Space Station is poised for liftoff Monday evening (U.S. time) from the Baikonur Cosmodrome in Kazakhstan.

Credit: NASA

Mounted on the same launch pad used by Yuri Gagarin to become the first human in space 50 years ago April 12, the Soyuz TMA-21 spacecraft was scheduled for launch at 6:18:20 p.m. EDT (GMT-4), the moment Earth's rotation carries the pad into the plane of the space station's orbit (4:18:20 a.m. April 5 local time).

Soyuz commander Alexander Samokutyaev, flight engineer Andrey Borisenko and NASA astronaut Ronald Garan planned to don their pressure suits around 2 p.m. (midnight local time) and to head for the pad shortly after 3 p.m. (1 a.m. local time) to strap in. Samokutyaev will make the climb to space in the central module's middle seat, with Borisenko to his left and Garan on his right.

For a program steeped in tradition and memories of its greatest triumph, a Soyuz launch so close to the Gagarin anniversary is a major event in Russia and a frequent topic at pre-flight briefings. The famed cosmonaut's face and name are painted on the side of the Soyuz rocket's upper stage.

"When I was a kid wishing to become a cosmonaut, it would never occur to me that I would have this chance, this opportunity, and I feel a great responsibility," Borisenko said in a NASA interview. "Great responsibility because I understand that our crew will be a symbol, an emblem of human success in space, and everybody will monitor what we do up there very closely.

"We'll have to show great work, right results, and also show that the time which has elapsed since the very first flight of Yuri Gagarin and Alan Shepard hasn't gone in vain, that we've learned something in space."

April 12 also is the 30th anniversary of the first shuttle flight, followed three weeks later by the 50th anniversary of Shepard's May 5, 1961, sub-orbital flight to become the first American in space. With the shuttle program's looming retirement after just two more missions and NASA's post-shuttle reliance on the Russians for access to orbit, the Cold War rivalry that gave birth to the space race has come full circle.

"It really is just an incredible honor to be a part of this anniversary in that I truly believe that on April 12th, 1961, humanity became a different species," said Garan, a retired Air Force colonel and F-16 pilot making his second space flight. "Humanity was no longer bounded to the confines of Earth on that day, and in 50 years since then we've made some pretty big steps and we've done some amazing things and I think we've pretty much cemented that we're not a one planet species, if we choose not to be a one planet species, anymore.

"And so, to launch so close to the 50th anniversary, from the same launch pad that Yuri Gagarin launched from, and then to be able to celebrate that anniversary on orbit and then to be able to celebrate the 30th anniversary of the (first) space shuttle launch and then the first American in space as well, I think is really going to be amazing. And it's such an honor that when we designed our Expedition 28 patch we included the name Gagarin and Shepard on it with the approval of their families to honor those two pioneers that basically helped us get us where we are today."

Assuming an on-time launch, Samokutyaev plans to oversee an automated docking at the Poisk module attached to the upper side of the Zvezda command module at 7:18 p.m. Wednesday. Waiting to welcome their new crewmates aboard will be Expedition 27 commander Dmitry Kondratyev, Italian astronaut Paolo Nespoli and NASA astronaut Catherine "Cady" Coleman, who were launched to the space station in December.

"This year in Russia is the year of cosmonautics and the prime minister of the Russian government is heavily involved in preparing the celebrations, and we think that this is a holiday, a day that everybody around the world should be celebrating," Samokutyaev said in a NASA interview. "We are very proud that we'll be able to participate in celebrating the 50th anniversary of the first human in space. We have planned several activities; we will not be discussing them first because this is a secret for now, and we'll be able to celebrate these important dates for everyone."

With the retirement of the space shuttle after two final missions, NASA will rely on Soyuz spacecraft to ferry U.S., European, Canadian and Japanese astronauts to and from the International Space Station until new commercial rockets and spacecraft are designed, built and tested.

NASA officials last month announced an extension to the agency's existing contract with the Russian Federal Space Agency covering crew transportation, rescue and related services from 2014 through June 2016. The contract is valued at $753 million and covers launch-through-landing support for 12 astronauts. Total cost for 42 U.S. and partner astronauts from 2007 through June 2016 is $2.25 billion.

Here is a timeline of the major launch-to-docking events for the Soyuz TMA-21 spacecraft (in EDT and mission elapsed time; source: NASA):

DD...HH...MM...SS...EDT...........EVENT

04/04/11       
                                       
00...06...00...00...12:18 PM......Batteries installed in booster
00...05...30...00...12:48 PM......State commission 'go'
00...05...15...00...01:03 PM......Crew arrives at site 254
00...05...00...00...01:18 PM......Tanking begins
00...04...20...00...01:58 PM......Spacesuit donning
00...04...00...00...02:18 PM......Booster is loaded with liquid oxygen
00...03...40...00...02:38 PM......Crew meets delegations
00...03...10...00...03:08 PM......Reports to the state commission
00...03...05...00...03:13 PM......Transfer to launch pad
00...03...00...00...03:18 PM......1st/2nd stage oxygen fueling complete
00...02...35...00...03:43 PM......Crew arrives at launch vehicle
00...02...30...00...03:48 PM......Crew ingress
00...02...00...00...04:18 PM......Crew in re-entry vehicle
00...01...45...00...04:33 PM......Re-entry vehicle hardware tested; suits are
..................................ventilated
00...01...30...00...04:48 PM......Hatch sealed and tested
00...01...00...00...05:18 PM......Launch vehicle control system preps; gyro activation
00...00...45...00...05:33 PM......Launch pad service structure halves lowered
00...00...40...00...05:38 PM......Suit leak checks;
..................................re-entry vehicle testing complete
00...00...30...00...05:48 PM......Emergency escape system armed
00...00...25...00...05:53 PM......Service towers retracted
00...00...15...00...06:03 PM......Suit leak checks complete; escape system to auto
00...00...10...00...06:08 PM......Gyros uncaged; on-board recorders activated
00...00...07...00...06:11 PM......Prelaunch operations complete
00...00...06...15...06:12 PM......Final launch countdown operations to auto
00...00...06...00...06:12 PM......Launch complex and vehicle systems ready
00...00...05...00...06:13 PM......CDR's controls activated; helmets closed;
..................................launch key inserted
00...00...03...15...06:15:05 PM...Combustion chamber nitrogen purge
00...00...02...30...06:15:50 PM...Booster propellant tank pressurization begins
00...00...02...15...06:16:05 PM...Ground propellant feed terminated
00...00...01...00...06:17:20 PM...Vehicle to internal; 1st umbilical tower sep;
..................................auto sequence start
00...00...00...40...06:17:40 PM...Ground power umbilical to 3rd stage separates
00...00...00...20...06:18:00 PM...Launch command given; central/side pod engines on
00...00...00...15...06:18:05 PM...Second umbilical tower separates
00...00...00...10...06:18:10 PM...Engine turbopumps at flight speed
00...00...00...05...06:18:15 PM...Engines at maximum thrust

00...00...00...00...06:18:20 PM...LAUNCH

00...00...08...45...06:27:05 PM...Orbital Insertion
00...03...47...30...10:05:50 PM...DV1 rocket firing (23.8 mph)
00...04...21...16...10:39:36 PM...DV2 rocket firing (45.5 mph)

04/05/11

01...00...36...33...06:54:53 PM...DV3 rocket firing (4.5 mph)

04/06/11

01...21...36...40...03:55:00 PM...US to Russian attitude control handover
01...21...52...40...04:11:00 PM...ISS maneuver to docking attitude
01...22...39...45...04:58:05 PM...AR&D automated rendezvous start (T0)
01...23...01...42...05:20:02 PM...AR&D DV4/Impulse 1 rocket firing (46.3 mph)
01...23...23...43...05:42:03 PM...AR&D Impulse 2 rocket firing (3.2 mph)
01...23...25...40...05:44:00 PM...Soyuz Kurs-A activation (T1)
01...23...27...40...05:46:00 PM...SM Kurs-P activation (T1)
01...23...46...05...06:04:25 PM...Range = 62 miles: Soyuz VHF-2 voice link
01...23...46...47...06:05:07 PM...AR&D DV5/Impulse 3 rocket firing (38.9 mph
01...23...50...37...06:08:57 PM...Daily Orbit 1 RGS AOS
01...23...50...45...06:09:05 PM...Range = 50 miles: valid Kurs-P range data
01...23...58...43...06:17:03 PM...Sunrise
02...00...11...25...06:29:45 PM...Range = 9.3 miles: Kurs-A & Kurs-P short test
02...00...13...40...06:32:00 PM...Daily Orbit 1 RGS LOS
02...00...18...05...06:36:25 PM...Range = 5 miles: Soyuz TV activation
02...00...25...38...06:43:58 PM...AR&D Impulse 4 rocket firing (14.5 mph)
02...00...29...45...06:48:05 PM...AR&D ballistic targeting point
02...00...31...30...06:49:50 PM...AR&D Impulse 5 rocket firing (8.1 mph)
02...00...33...22...06:51:42 PM...AR&D Impulse 6 rocket firing (3.9 mph)
02...00...35...24...06:53:44 PM...AR&D flyaround mode start
02...00...41...40...07:00:00 PM...AR&D stationkeeping start
02...00...50...40...07:09:00 PM...AR&D final approach start
02...00...52...40...07:11:00 PM...ISS inertial snap-and-hold window open
02...00...55...28...07:13:48 PM...Sunset

02...00...59...40...07:18:00 PM...DOCKING

02...01...00...40...07:19:00 PM...ISS inertial snap-and-hold window close
02...01...19...40...07:38:00 PM...Soyuz hooks closed
02...01...23...53...07:42:13 PM...Daily Orbit 2 Russian ground station AOS
02...01...30...16...07:48:36 PM...Sunrise
02...01...46...41...08:05:01 PM...Daily Orbit 2 Russian ground station LOS
02...02...11...40...08:30:00 PM...Russian to US attitude control handover

"Without the space shuttle, we wouldn't have this space station," Garan reflected. "Unfortunately, it'll be many decades before we have the capability that the space shuttle provides us right now. To have the vehicle that could fly to space, to carry the size and the weight of the payload that it can carry, to have its own robotic arm, its own airlock, and then to come back and land on a runway and bring things back that are the same weight and the same size and to bring those things back to Earth, that is a pretty tremendous capability.

"Unfortunately, we can't continue to do that and do all the other things that we want to do as well, so we had to make a very difficult decision to end the space shuttle program. Sometimes change is hard, and in this particular case it is hard, it's going to be a sad day when those guys land. ... But I truly believe that it's going to lead to bigger and better things and the space shuttle's place in history, I think, is fairly secure. It is an amazing spacecraft, amazing flying machine, and the many accomplishments that it's made throughout its history stand for themselves."