Hurricane-shortened spacewalk about to start
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: August 18, 2007
Canadian astronaut Dave Williams and space station flight engineer Clay Anderson are preparing for a shortened spacewalk today while their crewmates complete final equipment transfers to and from the station to clear the way for hatch closure later this afternoon. Concerned about the threat of Hurricane Dean, NASA managers have ordered the early hatch closure to protect the option of undocking Sunday and landing Tuesday, a day ahead of schedule, to get the shuttle back on the ground before mission control in Houston might have to be evacuated.
"Good Morning Endeavour! Thanks for the great day yesterday!" flight controllers said in a message uplinked to the crew early today. "You are an awesome crew! We are looking forward to the EVA today. As you were briefed last night, the EVA will be shortened so that hatch closure can take place this evening. You will undock tomorrow morning. Landing is being planned for Tuesday. This is all because of the potential threat to JSC posed by hurricane Dean. Thanks for your flexibility!"
Mission control commentator Rob Navias, however, said early today no final decisions have been made to undock Sunday and depending on updates to Hurricane Dean's projected track, mission managers presumably could change their minds. But barring a major change, the hatches will be closed around 5 p.m. today.
Today's spacewalk, scheduled to begin around 10 a.m., will be the 92nd since station construction began in 1998, the 15th so far this year and the fourth for Endeavour's mission. It will be the third for both Williams and Anderson. Going into today's EVA, 72 men and women had logged 562 days and 57 minutes of spacewalk time building and maintaining the international lab complex.
Items on today's agenda include installation of mounting brackets on the station's solar array truss to temporarily hold a shuttle heat shield inspection boom next year; retrieval of two space exposure experiment packages; get-ahead preparation of antenna gimbal locks; and installation of a wireless instrumentation antenna.
Anderson and Williams originally planned to carry out a six-and-a-half-hour spacewalk, but the revised flight plan shaved two hours off the excursion. Tasks that will be deferred to a future shuttle flight or to a station crew include work to tie down debris shields on the Destiny and Unity modules and a few other low-priority get-ahead tasks.
Here is the replanned timeline for today's activity (in EDT and mission elapsed time):
EDT........DD...HH...MM...EVENT 08/18/07 05:07 AM...09...10...30...STS/ISS crew wakeup 05:47 AM...09...11...10...EVA-4: Airlock repressurized to 14.7 psi 06:07 AM...09...11...30...EVA-4: Hygiene break 06:27 AM...09...11...50...EVA-4: Airlock depressurized to 10.2 psi 06:57 AM...09...12...20...EVA-4: Campout EVA preparations 08:27 AM...09...13...50...EVA-4: Spacesuit purge 08:42 AM...09...14...05...EVA-4: Spacesuit pre-breathe 08:57 AM...09...14...20...Logistics transfers resume 09:32 AM...09...14...55...EVA-4: Airlock depressurization 10:07 AM...09...15...30...EVA-4: Airlock egress and setup 10:22 AM...09...15...45...EVA-4: Orbiter inspection boom S1 mounting brackets installed 11:07 AM...09...16...30...Oxygen system tear-down 11:22 AM...09...16...45...EVA-4: EV3: S-band antenna sub-assembly gimbal locks 11:22 AM...09...16...45...EVA-4: EV3: MISSE space exposure experiment retrieval 12:07 PM...09...17...30...EVA-4: Wireless instrumentation system antenna installation 01:47 PM...09...19...10...EVA-4: Payload bay cleanup 02:12 PM...09...19...35...EVA-4: Airlock ingress 02:32 PM...09...19...55...EVA-4: Airlock repressurization 02:47 PM...09...20...10...Post-EVA spacesuit servicing 03:02 PM...09...20...25...MISSE disassembly 03:22 PM...09...20...45...MISSE transfer to shuttle 03:47 PM...09...21...10...Spacesuit transfer to shuttle 03:57 PM...09...21...20...Transfer tagup 04:47 PM...09...22...10...Farewell ceremony 05:02 PM...09...22...25...Hatches closed 05:27 PM...09...22...50...Rendezvous tools checkout 05:27 PM...09...22...50...Leak checks 08:07 PM...10...01...30...ISS crew sleep begins 08:37 PM...10...02...00...STS crew sleep begins
NASA's Mission Management Team will meet later today to evaluate Dean's progress and make a decision on when to undock. If the decision is to press ahead for a Tuesday landing, undocking would be targeted for 7:57 a.m. Sunday, setting up a landing back at the Kennedy Space Center around 12:29 p.m. Tuesday.
The astronauts originally planned to carry out a full-duration spacewalk today and finish up equipment and supply transfers to and from the lab complex Sunday. Hatches between Endeavour and the station were scheduled to be closed Sunday night to set the stage for undocking Monday. A now-routine post-Columbia final heat shield inspection was on tap Monday afternoon and the crew planned to pack up and test the shuttle's re-entry systems Tuesday. Touchdown at the Kennedy Space Center was targeted for around 12:52 p.m. Wednesday.
But Hurricane Dean has thrown a wrench into those plans because NASA may be forced to evacuate the Johnson Space Center early next week. If so, and if landing remained targeted for Wednesday, the agency would have to set up an emergency mission control center at the Kennedy Space Center. While controlling a shuttle from Kennedy is part of a long-established contingency plan, NASA would have to rely on a much smaller team and give up some of its ability to monitor the orbiter's myriad systems. By moving landing up a day, NASA likely could ensure a normal JSC-controlled re-entry.
But to land Tuesday, the Endeavour astronauts will have to finish equipment transfers today, during and immediately after the spacewalk, and close hatches between the two spacecraft this evening. The crew then could undock Sunday and have the normal two days to carry out a final heat shield inspection, test the ship's re-entry systems and pack up for landing.
"After the crew went to sleep, we spent a lot of time replanning Saturday and Sunday's timelines," said overnight flight director Heather Rarick. "To land on Tuesday, that means we'd have to undock on Sunday, which means we'd have to close the hatch on Saturday night. So we developed a plan for that. Most of the morning stays the same for that timeline. We will go out and do the EVA, we are going to shorten it if we need to so that we can get the crew back inside and be able to transfer the spacesuits and tools back to the shuttle and then close the hatch in the evening."
Endeavour carried some 5,000 pounds of equipment and supplies for the station. Another 4,000 pounds of hardware and no-longer-needed equipment were to be brought back to Earth on the shuttle. Rarick said the crew was ahead of schedule on transfer activity and most of the resupply work will be finished before hatch closure.
"There are a couple of things that we need to do late, so we've been holding off on them intentionally," she said. "One of the items is a cycle ergometer (exercise bike), we've brought a new one onto space station to replace the current one. But before we can send the old one home, we need to install it and check it out. So we have that on the timeline early (today)."
During today's spacewalk, Anderson plans to retrieve two space exposure experiment packages that will be moved into the shuttle for return to Earth.
"Other items we need to pack late is we have some experiments in the space freezer on space station and we need to put those in cooler bags so they can be brought home and kept at the proper temperature and we want to do that as late as possible in the flight," Rarick said. "So we have that timelined for late in the afternoon, just before the hatch gets closed."
In the crew's daily execute package of notes and flight plan changes uplinked from mission control, NASA's Mission Management Team gave the crew a big-picture overview of hurricane preparations.
"Hurricane Dean Preparations: The MMT received a briefing on the latest Hurricane Dean National Hurricane Center forecast track from the Spaceflight Meteorology Group. The projected track places the eye of a Category 4 storm in the Gulf of Mexico on Wednesday, FD15. Uncertainties in the forecast may change this prediction by +/- 6 hours. A low pressure system is forecasted to track west across the Gulf of Mexico from Florida to Louisiana. This low pressure system may influence the hurricane to take a more northerly ground track. Additionally, a more northerly track could lead to additional strengthening since the storm could miss the Yucatan peninsula entirely.
"JSC Senior Management will be meeting daily to assess the hurricane and will be making decisions appropriately. If the track of the hurricane holds to the forecast, it is expected that JSC will be closed on Monday, FD13, allowing non-mission support personnel to care for their families. All disciplines reporting to the MMT are preparing a list of mandatory support personnel that could support the remainder of the mission from JSC. The flight control team is making preparations to staff accordingly to support mission operations through landing."