Team Evaluates Possible Lightning Strike Near Pad

The space shuttle launch team is evaluating a possible lightning strike within one third of a mile from Launch Pad 39A at NASA's Kennedy Space Center. Engineers will review data to determine if the lightning affected space shuttle Atlantis or any of the pad's ground support equipment. A continuing band of thunderstorms has prevented teams from conducting a detailed pad inspection, which must be performed before the Rotating Service Structure can be rolled back from the shuttle.

After the rollback, the teams will continue work that must be performed before fueling Atlantis' external tank early tomorrow morning. The rollback originally was planned for 2 p.m. EDT.

At this morning's briefing, Shuttle Weather Officer Kathy Winters reported that the launch weather forecast remains unchanged, with a 30 percent chance of favorable weather for the 11:26 a.m. liftoff. The forecast is a more favorable 80 percent when the filling of the huge external fuel tank is set to begin.

At 5 a.m. this morning, the countdown entered a planned hold at the T-11 hour mark, and will resume at 7:01 p.m. tonight.

The astronauts had an early wakeup call as they continue to prepare for tomorrow's launch of Atlantis on the STS-135 mission to the International Space Station.

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Weather Delays Rotating Service Structure Rollback

Bad weather that moved into area of NASA's Kennedy Space Center in Florida has delayed the scheduled rollback of the Rotating Service Structure surrounding space shuttle Atlantis on Launch Pad 39A.

With the scheduled liftoff of Atlantis just one day away, Jeff Spaulding, NASA test director, Joe Delai, STS-135 payload manager, and Kathy Winters, shuttle weather officer, conducted the last countdown status briefing of the Space Shuttle Program this morning.

Winters reported that the launch weather forecast remains unchanged, with a 30 percent chance of favorable weather for the 11:26 a.m. EDT liftoff. The forecast is a more favorable 80 percent when the filling of the huge external fuel tank is set to begin.

"Our teams here and really all around the world have been working extremely hard for quite awhile on this particular mission to make sure the vehicle and the payload are ready for hopefully a magnificent launch on Friday," said NASA Test Director Jeff Spaulding.

At 5 a.m. this morning, the countdown entered a planned hold at the T-11 hour mark, and will resume at 7:01 p.m. tonight.

The astronauts had an early wakeup call as they continue to prepare for tomorrow's launch of Atlantis on the STS-135 mission to the International Space Station.

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Rotating Service Structure Move Set for Noon

At NASA's Kennedy Space Center, Launch Pad 39A's Rotating Service Structure now is targeted to roll back from space shuttle Atlantis at 12 p.m. EDT, two hours earlier than originally planned.

With the scheduled launch of Atlantis just one day away, Jeff Spaulding, NASA test director, Joe Delai, STS-135 payload manager, and Kathy Winters, shuttle weather officer, conducted the last countdown status briefing of the Space Shuttle Program.

Winters reported that the launch weather forecast remains unchanged, with a 30 percent chance of favorable weather for the 11:26 a.m. EDT liftoff. The forecast is a more favorable 80 percent when the filling of the huge external fuel tank is set to begin.

"Our teams here and really all around the world have been working extremely hard for quite awhile on this particular mission to make sure the vehicle and the payload are ready for hopefully a magnificent launch on Friday," said NASA Test Director Jeff Spaulding.

At 5 a.m. this morning, the countdown entered a planned hold at the T-11 hour mark, and will resume at 7:01 p.m. tonight.

The astronauts had an early wakeup call as they continue to prepare for tomorrow's launch of Atlantis on the STS-135 mission to the International Space Station.

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Countdown in Planned Hold; Briefing at 10 a.m. EDT

At 5 a.m. EDT, the countdown entered a planned hold at the T-11 hour mark, and will resume at 7:01 p.m. tonight.

This morning's countdown status briefing is scheduled for 10 a.m. The briefing will be carried live on NASA TV and online at www.nasa.gov/ntv. Panelists are Jeff Spaulding, NASA test director, Joe Delai, STS-135 payload manager, and Kathy Winters, shuttle weather officer.

The updated STS-135 launch weather forecast remains the same as yesterday, with a 30 percent prediction for favorable weather.

The STS-135 astronauts had an early wakeup call as they continue to prepare for tomorrow's scheduled 11:26 a.m. liftoff of space shuttle Atlantis on the final mission of the Space Shuttle Program.

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End of an Era: Weather Briefings and Communicating Uncertainty

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center (KSC) as the Launch Team prepares for the 8 July 2011 launch of Atlantis. You can find out more about the 45th Space Wing at their Facebook page.

We had two significant weather briefings Wednesday, 6 July: the 45th Space Wing Launch Readiness Review and the Shuttle Mission Management Team Launch minus 2-day meeting. Both meetings are essential to determine launch readiness, and weather is one piece of the large puzzle of things that must come together for launch. During these meetings, our squadron presents weather forecasts for the rotating service structure retract, tanking, solid rocket booster recovery, launch, plus 24- and 48- hour launch delay forecasts. Spaceflight Meteorology Group also presents the abort landing weather during the Shuttle Mission Management Team meeting. During the briefings, weather threats are highlighted so the Shuttle and Space Wing teams know what to expect. Sometimes NASA managers change the time of a pre-launch operation if the current schedule puts the launch countdown at risk for a weather delay, but the launch window itself is not modified since it is based upon the rendezvous with the International Space Station on-orbit.

After the Mission Management Team meeting, I attend a press conference with the Shuttle Launch Director, Mike Leinbach, and the Shuttle Launch Integration Manager, Mike Moses.  Our squadron Launch Weather Officers interact with them often since weather affects so many Shuttle operations. We provide a weather briefing to Mike Leinbach and his team every weekday morning to plan ground operations around the weather, if necessary. We increase the briefings to a few updates per day when a hurricane threatens the Florida East Coast. Mike Moses and Mike Leinbach have heard so many of my weather briefings that they can tell from the tone of my voice how certain or uncertain I am about a particular weather forecast. One NASA manager called this “Human Capital,” the rapport these managers build with their team which results in the synergy needed during a challenging situation, such as a Shuttle rollback decision.

Another way we describe the forecast confidence in a particular weather situation is through probability forecasts. For launch, we provide the “Probability of KSC Weather Prohibiting Launch,” as opposed to an absolute forecast. We also provide probabilities for constraint violations during ground operations.  In fact, many Shuttle constraints include probabilities, such as for Shuttle rollout, the constraint is “no more than a 10% chance of lightning within 20nm.” If you view our weekly planning forecast, you will see the probability of precipitation and lightning our customers use for planning purposes. These probability forecasts help launch teams make cost/risk decisions.

Speaking of probabilities, Wednesday, we increased our probability of KSC weather prohibiting launch. Weather does not look good for Friday here on the Florida Space Coast! Check out our latest launch forecast.  Hopefully we’ll be able to launch Friday—check out the photo that shows you the view of the Shuttle launch from our building!

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The End of an Era: Atlantis Launch Weather Outlook

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

It’s launch week and we are issuing our weather forecasts for the last Space Shuttle launch Friday, 8 July 2011.  The weather situation is interesting. A tropical wave located over the Turks and Caicos Islands is moving west-northwest toward Florida. These waves are typical this time of year, and as they move into Florida, they bring scattered showers and isolated thunderstorms behind them. We expect this wave to move into Florida on Thursday, the day prior to launch, as it rotates around the western side of the high pressure ridge north of the Central Florida area.  A tropical wave near the Turks and Caicos Islands will bring scattered showers and isolated thunderstorms to Florida Thursday. You can follow the development of the tropical wave in the Caribbean on the National Hurricane Center’s web site, tropical discussion.

Lingering moisture from the wave will still be prevalent in our atmosphere Friday providing ingredients for weather to develop as the sea breeze forms. The sea breeze will likely set up along the coast between 1000EDT and 1100EDT, early enough for weather to become an issue by the 1121EDT opening of the launch window. We expect cumulus clouds, showers, and even possibly a thunderstorm to develop which could violate our launch commit criteria or flight weather rules.  Given this situation, there is a 60% chance of Kennedy Space Center weather prohibiting launch Friday.  The primary concerns are showers or thunderstorms within 20 nautical miles of the Shuttle Landing Facility and cumulus clouds within 10 nautical miles (nm) of the launch pad.

Another weather phenomenon we have potential for this week is an offshore waterspout. On summertime mornings when we have a south-southeasterly flow with very weak winds through a moist atmosphere, waterspouts sometimes develop offshore of the Kennedy Space Center coast. These waterspouts are not damaging like tornadoes and usually have winds 30-45 knots. You wouldn’t want to drive your boat through one of these, but we issue weather advisories for these types of waterspouts (as opposed to a tornado warning) so the personnel at Kennedy Space Center know they are not a threat to life and property like a classic tornado.  Although there are no launch commit criteria or flight rules associated with waterspouts, the cumulus clouds above them might be a concern! You can learn more about Florida waterspouts from NOAA.

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Launch Weather Forecast Remains 30 Percent "Go" for Friday

Following a meeting of the Mission Management Team this morning, STS-135 countdown and weather updates were provided at prelaunch news conference. Panelists included Mike Moses, Mission Management Team chair and space shuttle launch integration manager, Mike Leinbach, shuttle launch director, and Kathy Winters, shuttle weather officer.

"We had a really smooth Mission Management Team meeting today," said Moses. "The vehicle is in fantastic shape." In regard to the launch-day weather forecast, he added, "Before we go load the propellants into the tank we'll take a look at the weather and make sure it's really a good day to try that, and so at that point we'll be making a decision"

"The countdown so far is going extremely well," reported Leinbach. "We're not tracking anything at all that would prevent an on-time liftoff Friday morning."

"We have a tropical wave that's out in the Caribbean," explained Winters. "That wave is actually going to come into Florida along with a lot of tropical moisture that's down to the south, and it's all going to roll into Florida in the next couple of days." Based on these conditions, Winters predicted an 80 percent chance of weather preventing tanking operations, with a 70 percent chance of it standing in the way of launch at 11:26 a.m. on Friday.

The countdown for this final space shuttle launch began yesterday at 1 p.m. This morning at the T-27 hour mark, the countdown entered a planned hold at 5 a.m. and resumed at 9 a.m.

The Atlantis astronauts awoke at 4:30 a.m. to continue their preparations for launch.

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Countdown Continues Toward Friday's Launch

The countdown for the final space shuttle launch began yesterday at 1 p.m. EDT, starting at the T-43 hour mark. However, the weather forecast looks less than favorable for Friday's launch, with only a 30 percent chance of a "go" at the 11:26 a.m. liftoff time.

At the 10 a.m. precountdown status briefing yesterday, NASA Test Director Jeremy Graeber reported space shuttle Atlantis is ready for flight, and STS-135 payload manager Joe Delai said the payloads are ready to go as well. The only issue standing in the way of liftoff is the chance of showers and thunderstorms developing along the sea-breeze front reported by Kathy Winters, shuttle weather officer.

Today's prelaunch news conference will begin at 11:30 a.m. EDT live on NASA TV and online at www.nasa.gov/ntv. Participants will be Mike Moses, Mission Management Team chair and space shuttle launch integration manager, Mike Leinbach, shuttle launch director, and Kathy Winters, shuttle weather officer.

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STS-135 Countdown Begins at 1 p.m. Today

The countdown for the final space shuttle launch begins today at 1 p.m. EDT, but the launch-day weather forecast looks less than favorable.

At the 10 a.m. pre-countdown status briefing this morning, NASA Test Director Jeremy Graeber reported space shuttle Atlantis is ready for flight, and STS-135 payload manager Joe Delai said the payloads are ready to go as well. The only issue standing in the way of liftoff on Friday is a 60 percent chance of showers and thunderstorms developing along the sea-breeze front reported Kathy Winters, shuttle weather officer.

After flying to NASA's Kennedy Space Center in Florida yesterday, the STS-135 astronauts today are reviewing their flight data file and conducting checks of their launch and entry suits.

At Kennedy's Launch Pad 39A, technicians have completed space shuttle Atlantis' aft confidence checks and final preparations of the main propulsion system.

Despite storms in the area over the extended weekend, there were no reports of adverse weather or lightning strikes inside the launch pad

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Briefing Under Way

NASA TV is carrying the Precountdown Status Briefing live. Briefing participants are Jeremy Graeber, NASA test director, Joe Delai, STS-135 payload manager, and Kathy Winters, shuttle weather officer. The briefing is live online at www.nasa.gov/ntv.

The countdown for the final space shuttle launch begins today at 1 p.m. EDT. The STS-135 astronauts flew to NASA's Kennedy Space Center in Florida yesterday. Today the crew members will review their flight data file and conduct checks of their launch and entry suits.

At Kennedy's Launch Pad 39A, technicians have completed space shuttle Atlantis' aft confidence checks and final preparations of the main propulsion system.

Despite storms in the area over the extended weekend, there were no reports of adverse weather or lightning strikes inside the launch pad.

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Countdown Begins Today

The countdown for the final space shuttle launch begins today at 1 p.m. EDT. The STS-135 astronauts flew to NASA's Kennedy Space Center in Florida yesterday. Today the crew members will review their flight data file and conduct checks of their launch and entry suits.

At Kennedy's Launch Pad 39A, technicians have completed space shuttle Atlantis' aft confidence checks and final preparations of the main propulsion system.

Despite storms in the area over the extended weekend, there were no reports of adverse weather or lightning strikes inside the launch pad.

At 10 a.m. EDT this morning, NASA TV will carry the Precountdown Status Briefing live. Briefing participants will be Jeremy Graeber, NASA test director, Joe Delai, STS-135 payload manager, and Kathy Winters, shuttle weather officer. The briefing can be seen online at www.nasa.gov/ntv.

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Countdown to Endeavour: Lightning Protection Is a Must

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

As launch day approaches, we are expecting thunderstorms to impact the Florida East Coast, some which could produce severe weather. When meteorologists use the word “severe weather,” we aren’t talking about the everyday, afternoon thunderstorms. Severe weather indicates thunderstorms could produce winds 50 knots or greater, hail, and/or tornadic activity.  If severe weather occurs, the Shuttle team inspects the vehicle to ensure weather has not caused any damage. Also, if we have close lightning strikes, we provide detailed lightning data to ensure the team knows if the strike potentially caused damage to the shuttle or any launch pad ground systems.

Lightning protection for launch complexes is a must, and the Kennedy Space Center and Cape Canaveral Air Force Station launch pads have a significant amount of lightning protection to protect vehicles and launch pad structures from damage due to lightning strikes. For the Shuttle launch pad, a 1-inch thick grounded wire stretches 1000 feet each direction from the 80-foot fiberglass mast at the top of the structure. A 4-foot lightning rod extends from the mast. All structures on the pad are grounded, including the Mobile Launch Platform. The hydrogen, oxygen, and water storage tanks provide their own ground, and a gridwire system protects hypergolic fuel storage areas. Overall, the area is well protected to minimize damage from lightning.

To learn more about lightning, check out the National Severe Storms Laboratory.

Luckily, by launch day, the weather should be off to our east, and our main concerns are a low-cloud ceiling and a crosswind at the Shuttle Landing Facility for abort landing weather. Wish us luck!

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Teams Not Working Any Launch Issues, Post-MMT News Conference at 4 p.m. Eastern

Launch teams at NASA’s Kennedy Space Center are working through the countdown milestones with no issues that would delay space shuttle Endeavour’s launch Monday, May 16 at 8:56 a.m. EDT to the International Space Station. The countdown entered an 8-hour built-in hold at 11 a.m. at T-19 hours and will pick up again at 7 p.m. Technicians at Launch Pad 39A have completed loading cryogenic reactants into Endeavour’s fuel cell storage tanks. Teams will remove the orbiter mid-body umbilical unit, which was used to load the propellants into the power reactant distribution system later this afternoon.

Current forecasts still call for a 70 percent chance of acceptable conditions at launch time.

The Mission Management Team will meet at 3 p.m. MMT chair and Space Shuttle Launch Integration Manager Mike Moses, Shuttle Launch Director Mike Leinbach and Shuttle Weather Officer Kathy Winters will hold a news conference at 4 p.m. live on NASA TV and www.nasa.gov/ntv.

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Countdown to Endeavour: Launch Attempt Number Two

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

We are getting ready for launch again. The NASA team replaced and re-tested the Load Control Assembly-2 in the aft section of the vehicle, and we are back in the 3-day countdown. Today we issued the launch forecast, Ice Team Forecast, Solid Rocket Booster Recovery forecast, and I briefed weather to the Launch Director and at the Countdown Status press conference. Like I mentioned before, this is like a “do-over.” We have the same forecasts to accomplish during the days prior to launch. Since this is now a morning launch (8:56 AM Eastern Daylight Savings Time), the schedule shifts a bit, and we actually started issuing launch forecasts on Thursday, L-4 days before launch rather than L-3 days. We will basically be working a night shift for launch, but our Launch Weather Team has required crew rest rules to ensure everyone is sharp for their launch shift.

We are, again, expecting weather to impact the pre-launch operations. Sunday, a front will move into Florida, and we are concerned about thunderstorms in the area for the Rotating Service Structure (RSS) retract operations. This happened during our last launch attempt, and the team had to wait 5 hours to rotate the RSS. Since the Shuttle team knew the weather was going to be a problem, they did some ‘get-ahead’ work and were still able to begin tanking on time. Hopefully the weather won’t delay them 5 hours again! Still, I am sending regular exposure forecasts to the team so they can plan operations around the weather. Luckily, by launch morning, the weather improves. We are forecasting a 30% chance of local weather prohibiting launch due to a possible crosswind violation at the Shuttle landing facility for the Return to Launch Site (RTLS) abort landing weather and potential for a low-cloud ceiling. Overall, the weather is favorable. Hopefully we will launch as scheduled Monday because the weather looks worse for Tuesday morning as another front moves into Florida.

In addition to launch preparations, we also preparing for hurricane season which begins 1 June! We are preparing a simulation for the Kennedy Space Center Senior Staff as well as well as several briefings to KSC emergency managers and the Shuttle team. The last Shuttle launch vehicle, STS-135 Atlantis, will be on the launch pad during hurricane season, and the Shuttle team is well prepared with detailed timelines of the schedule required to prepare and roll back the Shuttle if a hurricane threatens the area. This is not a quick process! Just preparing for the roll takes almost 2 days, and the roll itself takes 6 hours.  When we have a storm threatening the area, we work closely with the National Hurricane Center to provide as much information to the Shuttle team as possible so they can determine the best course of action.

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45th Weather Squadron Focuses on Atlas Launch

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

With the Shuttle Endeavour launch date postponed until repairs are complete, the 45th Weather Squadron is focused on the Altas V launch Friday, 6 May 2011.  Clay Flinn is the Launch Weather Officer for the Atlas V and has been issuing launch forecasts and providing weather support to the 45th Space Wing and United Launch Alliance teams all week. On Thursday, 5 May, the weather was favorable, and the team rolled the Atlas V to the launch pad. On Friday, afternoon cumulus clouds including possibly thunderstorms are expected; the question is whether they will occur during the early-afternoon launch window. See the launch forecast link for the latest information.

During the Atlas V launch countdown, our weather forecasters will still issue watches, warnings, and advisories for Kennedy Space Center and Cape Canaveral Air Force Station. We issue lightning watches and warnings for each launch complex and processing area individually so that, even if a thunderstorm is occurring over one area, unless there is lightning within 5 nautical miles, other areas can continue work. If a lightning strike occurs close to one of our launch vehicles, we send the launch team information about the lightning strike from our Cloud-to-Ground Lightning Surveillance System. The launch team then decides if the strike requires vehicle systems tests or inspections. Of course, any lightning strike within 10 nautical miles of the Atlas V launch path will violate the lightning launch commit criteria.

Hopefully the weather will cooperate for the Atlas V launch!  Launches from the Florida Space Coast are truly a sight to see!

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Launch Preparations on Track; RSS Rollback Scheduled for Tonight

Preparations for space shuttle Endeavour's launch are continuing as planned at NASA Kennedy Space Center's Launch Pad 39A. STS-134 Commander Mark Kelly and his crew also are continuing their prelaunch activities. Liftoff to the International Space Station is scheduled for 3:47 p.m. EDT Friday.

The weather forecast calls for a 70 percent chance of favorable conditions at launch time, according to Shuttle Weather Officer Kathy Winters. The only concerns for launch may be the crosswinds at the Shuttle Landing Facility and a low cloud ceiling associated with a front moving into Central Florida.

The rotating service structure (RSS) is scheduled to be retracted at 7 p.m. today but may be delayed because of possible storm activity over the center. Teams will have about a four-hour leeway for the storms to clear out with no affect on Friday morning's external tank fueling, now planned for 6:22 a.m.

The U.S. Fish and Wildlife Service is in the process of performing an aerial survey of yesterday's brush fire, which was southeast of the Turn Basin and about three miles from the launch pad. The brush fire now is fully contained, and the plan is to burn off the remaining fuel within the fire area to help eliminate any smoke on launch day.

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Countdown to Endeavour: Rockets Can Trigger Lightning Strikes

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

I took a picture of this cumulus cloud from the press site on Tuesday morning after the countdown status briefing. Clouds like this formed along the sea breeze due to our moist atmosphere. Although these clouds are normally harmless, on launch day the 45th Weather Squadron Launch Weather Team actually pays close attention to the height of any cumulus clouds like these that develop within 10 nautical miles of the launch pad. If a cumulus cloud gets tall enough, it may violate our cumulus cloud rule, one of the many rules in our Launch Commit Criteria. The purpose of the cumulus cloud rule is to prevent the threat of triggering a lightning strike when launching into elevated electric fields in the atmosphere. Fortunately, we do not expect significant cumulus clouds to be in the area this Friday.

Did you know a rocket can trigger a lightning strike when there is no natural lightning occurring? The Lightning Launch Commit Criteria protect the Shuttle and other rockets from the threat of triggered lightning. See how scientists at the University of Florida study triggered lightning by launching rockets into elevated electrical fields.

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STS-134 Prelaunch Update

At today's pre-launch countdown status briefing held at NASA's Kennedy Space Center in Florida, managers reported space shuttle Endeavour, its payload and crew are ready for launch at 3:47 p.m. EDT Friday.

NASA Test Director Jeremy Graeber reported everything is progressing on schedule for the 25th and final launch of space shuttle Endeavour.

"Our teams here at Kennedy Space Center, and at NASA centers around the country, have been working for over a year to get Endeavour ready for the STS-134 mission," said Graeber. "We're not working any issues at this time … and over the past ten days have completed some major milestones."

Joe Delai, STS-134 payload manager gave a brief overview of the payload and will have more details during Thursday's launch countdown briefing. "The payloads are closed for flight, we're not working any issues and ready to support launch," said Delai.

Shuttle Weather Officer Kathy Winters reported weather is looking good for launch day and for the loading of propellants into Endeavour's external fuel tank although there may be possibility for a storm during the rollback of the rotating service structure, or RSS, scheduled for 7 p.m. Thursday.

At this time there's only a 20 percent chance of weather hindering a successful launch on Friday, due to possible windy conditions, reported Winters.

Endeavour's six astronauts departed Ellington Field, Texas, shortly before 10 a.m. EDT. They are expected to arrive in their T-38 jets at NASA Kennedy Space Center's Shuttle Landing Facility at 12:15 p.m. Their arrival will be aired on NASA TV (www.nasa.gov/ntv).

Today at 2 p.m. NASA's official launch countdown clock begins counting backward toward Friday's liftoff.

Tomorrow's pre-launch news conference will be aired at 11 a.m. on NASA TV (www.nasa.gov/ntv).

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Countdown to Endeavour: Moving the External Tank Barge

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

When the External Tank Barge “Pegasus” is not transporting external tanks from the Michoud Assembly Facility in New Orleans to Kennedy Space Center, it resides in the Vehicle Assembly Building basin between the Kennedy Space Center Press Site and the Shuttle launch pad. Due to this location and its size, the barge blocks the view of the launch from the press site; therefore, the United Space Alliance Marine Operations team must move the barge out of the way by launch day. 

The team uses small motor boats to move the barge, but needs winds 5 knots or less so the boats can move the barge, not vice-versa. Because of this low wind constraint, weather is the main factor when scheduling the move. We’ve been looking for a window of opportunity for this barge move for over a week, and we finally decided that Thursday, April 21 was the best day. Forecasting such light winds on spring mornings can be challenging. I hoped our wind forecast was correct and was touching base with the marine operations team every morning with updates. Luckily, the winds cooperated, and the team moved the barge across the basin. The press site now has a perfect view of the launch to relay to the world.

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Countdown to Endeavour: How to Move a Solid Rocket Booster Segment

By Carla Voorhees

Kathy Winters is an Air Force Civilian Meteorologist at the 45th Weather Squadron at Cape Canaveral Air Force Station. She is the Space Shuttle Launch Weather Officer providing weather support to the Space Shuttle Program at Kennedy Space Center as the Launch Team prepares for the 29 April 2011 launch of Endeavour. You can find out more about the 45th Space Wing at their Facebook page.

Example of a segment move photo from the Kennedy Space Center Multimedia Web Site - http://go.usa.gov/TJC

On April 13, 2011, we had our last Solid Rocket Booster “segment move” for the final Shuttle mission launching in June. The solid fuel segments arrive on rail from the ATK solid rocket booster plant in Promontory, Utah, to the Rotation Processing Surge Facility at Kennedy Space Center, just north of the Vehicle Assembly Building (VAB). The segments are then transported to the VAB for stacking.

The transport to the VAB requires no more than a 25% chance of lightning during the hour it takes to move the segment. Luckily, the weather was favorable that morning, and the team completed the transport successfully.

This operation is an example of how the 45th Weather Squadron provides time and location-specific forecasts. During the summertime thunderstorm season, breaking down the forecast into hourly increments is imperative to providing the team with a safe window of opportunity to complete the operation.

The 45th Weather Squadron provides the forecast, and the Shuttle team determines whether the operation is a “Go” or “No-Go” given their specific weather constraints.

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