Cosmonaut Sergei Krikalev works with cameras in the Zvezda service module, while astronaut Bill Shepherd busily goes about chores in the background. The photograph was taken by Yuri Gidzenko using an electronic still camera. This was one of the first still pictures to be downlinked from the station since the Expedition One crew boarded it earlier in the week. Photo: NASA

NASA managers are holding open the option of delaying launch of the next space station assembly flight if the lab's on-board crew is unable to completely unload a Progress supply ship in time.

Carrying two tons of equipment and supplies, the Progress M1-4 vehicle is scheduled to dock at the Zarya module's normally downward-facing nadir port at 0306:34 GMT Saturday (10:06:34 p.m. EST Friday).

After taking Saturday and Sunday off, commander William Shepherd, Yuri Gidzenko and flight engineer Sergei Krikalev plan to begin unloading the supply craft in earnest.

The shuttle Endeavour, meanwhile, is poised for blastoff Nov. 30 on station assembly flight 4A. The goal of the 101st shuttle mission is to deliver a huge set of solar arrays to the station to boost its power generating capability.

The shuttle will dock with pressurized mating adaptor No. 3 on the U.S. Unity module's nadir port. Because of the proximity of the two nadir ports, the Progress vehicle must be jettisoned before Endeavour can dock.

That gives the crew until Dec. 1 to unload the spacecraft, keeping track of where everything is put along the way, and to load it back up with trash and no-longer-needed equipment.

"Sunday will be an off duty day. Saturday will be an off-duty day, off duty in the sense that we don't have any demands that we place on them," said station flight director Jeff Hanley. "That doesn't mean they won't get into the Progress and start to pull out particular items.

"The ground teams have sent things like fresh produce and other things the crew would like to have for their off time. I think we will see them getting into the Progress, getting those things out and perhaps doing some get-ahead work if they so choose, but no expectations are placed on them by the ground."

Crews aboard the Mir space station typically took a month or more to completely off load a Progress supply ship. While Hanley said he expects the ISS crew to complete the work in time for mission 4A, "we always have the option of slipping the 4A launch if we don't get that work done for whatever reason."

"We obviously don't want to throw away valuable dry cargo or other resources like oxygen and propellant," Hanley said. "So obviously, we'll be looking very hard at what the right time to launch 4A would be. One of our launch commit criteria for 4A is that the Progress is closed out and ready to depart for launch of the shuttle. That could, in essence then, drive a launch slip."

Gidzenko, Soyuz commander for Expedition One, is pictured onboard the space station during the first week of occupancy by the three-man crew. Photo: NASA

Engineers have looked at the feasibility of undocking the Progress and then redocking it after Endeavour departs. But because a critical antenna system is retracted during the initial docking sequence, a second docking would have to be manually carried out by Soyuz pilot Yuri Gidzenko, operating a remote control system in the Zvezda module.

Because that system is not redundant, "that wouldn't be an option," Hanley said. "So yes, we would probably delay the 4A launch if we didn't get that work done."

The TORU manual guidance system will be available as a backup Friday evening during the Progress vehicle's automatic approach. Should the automatic system fail, Gidzenko will be able to take over, using a joysticks and a television system that will show him the view from the Progress.

"The TORU system is a control panel, a TV monitor and a set of hand controllers in the service module, just aft of the central post on the starboard side," Hanley said. "Yuri will be sitting at the controls of that system. They'll likely dim the lights to make sure that his eyes, that he has the best possible contrast with the TV monitor he'll be using to monitor the approach.

"He gets a TV signal from the approaching vehicle and can monitor what that vehicle sees and will be able to use that TV camera to guide the vehicle up to the station if that automated system does not work."

For docking, the station will be oriented in what NASA calls an "x-pop 180" orientation. The station will be flying with its long axis perpendicular to the direction of travel with Unity facing the north side of the orbital plane and Zvezda facing south.

The station normally flies with the nadir ports, as their name implies, facing Earth. For the Progress docking, however, the station will be rolled 180 degrees about its long axis to put the nadir ports on top. That will permit the sun to warm up the Zarya module's docking mechanism.

The crew will get the weekend off, but it will be work as usual during the American Thanksgiving Day holiday next Thursday. While several U.S. and Russian holidays will be observed during the crew's stay, Thanksgiving isn't one of them.

On the other hand, Hanley said the crew's work schedule has settled down and that the pace of life aboard the station is much more "moderate" now than it was during the hectic first few days aboard the outpost.

"They certainly have time in the day to get the tasks done that are asked of them," he said. "We're working very hard ... to get them the information necessary to do the tasks that are on the plan. I think we're doing better at that than we did the first week.

"But also that first week was a very demanding week because of all the life support systems that had to be outfitted in a relatively short amount of time. ... The pace we've now settled into here in the second week and on into the third week, I think you'll continue to see a rather even pace for the crew up until the 4A mission."

The official portrait of Expedition One: Commander William M. (Bill) Shepherd (center) is flanked by Soyuz Commander Yuri P. Gidzenko (right) and Flight Engineer Sergei K. Krikalev (left). National flags representing all the international partners run along the bottom. Photo: NASA

The crew was informed this afternoon that Russia now formally plans to deorbit the Mir space station next February. They had no immediate reaction.

But Hanley said as a flight controller, "I share a certain feeling of empathy with my Russian counterparts in seeing the Mir program end."

"I think they've done an incredible job keeping the Mir flying well beyond its design life and it's really a testimonial to the capabilities of the Russian team to keep a complex piece of machinery like that flying for so many years beyond its design life," he said. "So I have great admiration for the job that they've done."