Jump to the most recent addition.

The next crew destined for duty at the International Space Station, and the shuttle crew that will taxi them there, have arrived at the Kennedy Space Center -- but it's still unclear if they will get to launch on time on Thursday.

That's because engineers continue to study a potential problem related to the hydraulic system of the space shuttle's solid rocket boosters. At this point officials are unsure if the problem detected on other hardware could be present in the equipment now installed on Discovery's booster rockets.

Depending on what a review of paperwork, inspections and further tests show, the options include replacing the suspect hardware or flying the shuttle "as is." If Discovery's boosters must be worked on, the effort likely will delay the launch three or four days.

A decision could come as early as tonight when shuttle program managers convene a telecon to discuss the matter. It's also possible they will need more time to study the issue, in which case the countdown would begin as planned on Monday and a decision to scrub would come later in the week.

The standard three-day space shuttle countdown began here at the Kennedy Space Center at 5 p.m. EDT today after program managers decided Discovery's solid rocket boosters were safe to fly. (See related story.)

Things look fairly good for launch Thursday in terms of weather. Officials say there is a 60 percent chance conditions will be acceptable during the five-minute launch window.

Among the activities early in the countdown is a review of the shuttle's flight software and loading the backup flight software into Discovery's computers.

On Tuesday the launch team will begin activating and testing the shuttle's navigation systems, and later will load liquid hydrogen and liquid oxygen into tanks on board Discovery -- chemicals that will be combined in space to generate electricity and drinking water for the crew.

Nothing much to report this morning following NASA's shuttle countdown status briefing for news media.

Technically everything looks to be in a good shape with only a couple of minor concerns that are not expected to be showstoppers, and there is no significant change to the weather forecasts, which remain more optimistic than not.

The big ticket item for today at the launch pad will be to load the cryogenic reactants -- liquid hydrogen and liquid oxygen -- into storage tanks located under Discovery's cargo bay. These chemicals are combined within fuel cells in space to generate electricity for the mission.

Stay tuned to this page for updates to the countdown and complete mission coverage.

Two minor leaks in ground equipment overnight put the NASA launch team a couple of hours behind schedule but officials say they won't have any trouble catching up and being ready to go on Thursday.

The leaks were in the plumbing required to fill Discovery's onboard tanks with liquid hydrogen and liquid oxygen, which are combined in space to generate electricity for the crew.

Officials also reported this morning that inspections of Discovery's rear engine compartment -- which had been closed for flight but was quickly opened for the last-minute checks -- are good and the extra work did not put them behind. The checks were ordered because of a concern seen on another vehicle, but nothing was found.

Meanwhile, the weather forecast continues to predict a 60 percent chance of acceptable conditions during the 5-minute launch window.

Stay tuned to this page for updates to the countdown and complete mission coverage.

The effort to fill shuttle Discovery's external tank with its half-million gallons of liquid hydrogen and liquid oxygen propellant began at 8:20 a.m. EDT after mission managers approved continuation of the countdown.

Two minor issues were noted and cleared at this morning's Mission Management Team meeting.

The first has to do with the inflatable emergency escape slide the crew would use to leave the orbiter in the event of a contingency on the ground. A slide recently used in training in Houston did not properly inflate, so officials wanted to make sure the same thing wouldn't happen on Discovery and reviewed the designs of the two slides to ensure that fact.

The second issue involves the lipstick-sized cameras that have been used during recent countdowns to show the astronauts taking their seats inside the shuttle. The video system isn't working, apparently because of an issue with cables that are located deep in the guts of the Mobile Launch Platform the shuttle is now sitting on.

A repair would take too long so officials decided to forgo the photo opportunity.

Meanwhile, the weather forecast continues to predict a 60 percent chance of acceptable conditions during the 5-minute launch window, with rainshowers and possible thunderstorms the concern. At launch time on Wednesday the skies were crystal clear and it is sunny this morning, but this is Florida so things can rapidly change.

Stay tuned to this page for updates to the countdown and complete mission coverage.

Shuttle Discovery's rust-colored external tank is filled with its load of cryogenic propellant and is now in what NASA calls "stable replenish" mode. That means that as liquid hydrogen and liquid oxygen naturally boils away inside the tank, a fresh supply of the supercold chemicals is introduced into the system. The gaseous hydrogen "exhaust" is burned by a so-called flare stack, while the gaseous oxygen is vented into the open air and is seen as the bright white vapor streaming away from the vehicle.

Weather officials continue to forecast a 60 percent chance of acceptable conditions during the five-minute launch window. Clouds are starting to build over Central Florida as the afternoon sun heats up the atmosphere. Hopefully the sea breeze will keep the clouds far enough away to allow the launch this afternoon.

Meanwhile in space, the Expedition Two crew aboard station Alpha are preparing for their return home and the frontier outpost is in good shape for Discovery's planned arrival on Saturday.

The station did experience another computer hiccup this week when one of the backup command and control units could not access its hard drive, but flight controllers quickly resolved the issue, which happened while the three-member crew were asleep. NASA officials say it is of no consequence to Discovery's mission. In fact, the shuttle will be carrying up a spare computer for the station.

Stay tuned to this page for updates to the countdown and complete mission coverage.