International space station towers above the Endeavour. Photo: Spaceflight Now/NASA TV

NASA and Russian Space Agency managers reached a last-minute compromise late Friday that will allow U.S. millionaire space tourist Dennis Tito to blast off for the international space station on schedule Saturday.

But if U.S. efforts to fully revive the space station's still-crippled central computer system are not wrapped up in time to permit Endeavour's crew to undock Sunday - one day later than originally planned - the astronauts will stay a second extra day and Tito's crew will cool its heels in a parking orbit for an additional 24 hours.

While the compromise suits the needs of both parties, the difficulty they had reaching a decision appeared to many observers as evidence of a deepening rift between the two major players in the space station project.

But Bill Gerstenmaier, deputy director of the station project at the Johnson Space Center in Houston, said that's not true down in the trenches where U.S. and Russian space engineers were in agreement about the best course of action.

"I don't think it's that symptomatic of a major problem between us," he said. "I think the thing that's good is when we ended up explaining to the Russians yesterday, technically, at the mission management team meeting, exactly where we were, the technical guys in the control center in Moscow were in 100 percent agreement with where we were going, they were in 100 percent agreement with what we were going to have to do technically. We're in synch together.

"So from my perspective, that was very good," he continued. "We both recognized the difficulties we each had and we were looking a mutual ways to fix those problems between both of us. So it may appear strained from the outside looking in, but from the inside, technically, I think we're working together very well."

The key word is "technically."

From a program management point of view, however, many NASA insiders were clearly angered it took so long to reach an agreement that in hindsight would appear to be a win-win solution for both sides.

Gantries raise around the Soyuz TM-32 rocket after its arrival at the launch pad on Thursday. Photo: Anatoly Zak/Spaceflight Now

The Soyuz TM-32 vehicle is scheduled for liftoff from the Baikonur Cosmodrome in Kazakhstan at about 3:38 a.m. EDT Saturday. Docking with the space station is targeted for roughly 4 a.m. Monday after a normal two-day rendezvous sequence.

Endeavour's crew originally planned to undock Saturday, but the computer glitches that crippled the station earlier this week prompted NASA managers Thursday to extended the docked portion of the flight by at least one day.

NASA could do that on its own because a one-day extension would have no impact on the Soyuz TM-32 vehicle's docking Monday.

But NASA managers, concerned about the overall health of the space station's computer system, wanted a second additional docked day to continue troubleshooting and provide a backup communications link to the station in case of subsequent failures.

As a result, the Russians were asked to delay Tito's launch by one day. There was no immediate response - Gerstenmaier blamed the time zone difference for part of the problem - and the rocket fuel hit the fan.

News accounts indicated the Russians would press ahead with an on-time launch regardless of NASA's objections. Other Russian officials were quoted saying the station's computer problem had been resolved and there was no need for a mission extension.

NASA officials grimly pressed ahead and in the end, a compromise emerged when the Russians finally offered to extend the Soyuz rendezvous if required.

"After a series of discussions today, NASA and the Russian Aviation and Space Agency (Rosaviakosmos) reached a decision on the launch date for the Soyuz 2 taxi mission and subsequent on-orbit activities," NASA said in a statement.

"Rosaviakosmos will launch the Soyuz 2 as scheduled Saturday, April 28, and has agreed to delay the Soyuz's docking to the International Space Station if additional time is required to resolve command-and-control computer problems aboard the station.

"Today's decision will ensure continued safe operations aboard the international space station and provide for the timely arrival of the replacement Soyuz lifeboat," the statement continued.

"While the international space station and space shuttle teams have made significant progress, mission managers are trying to resolve the computer issue by tomorrow. The Russian proposal to delay Soyuz docking, if required, provides critical flexibility to the mission management team."

Endeavour's robotic arm grapples the Raffaello module for detachment from the space station on Friday afternoon. Photo: Spaceflight Now/NASA TV

Wayne Hale, a veteran shuttle flight director, said NASA's goal is to leave the space station with a fully operational S- and Ku-band communications system and what amounts to two-and-a-half of its three central command-and-control computers intact.

As of this writing, C&C-2 is fully operational. C&C-1, which suffered a hard drive failure Tuesday night, is being replaced with a laboratory module experiment control computer that will be loaded with C&C control software. Engineers plan to uplink the software overnight and if all goes well, the computer will be on line and operational by Saturday morning.

C&C-3 also has hard drive problems. But Hale said ground controllers plan to re-initialize that machine and load as much C&C software as possible into the computer's DRAM memory, isolating the faulty hard drive. The disk will be replaced later.

With two operational C&C computers, the station astronauts will power up the new Canadarm 2 space crane Saturday and complete a long-delayed operation to hand a no-longer-needed cargo pallet back to the shuttle's robot arm for reberthing in Endeavour's payload bay.

The Canadarm 2 then will be parked and powered down. The astronauts will forego a series of previously planned tests, including a dry run to practice the movements and procedures needed to install the station's main airlock in June.