+ L-3 Weather Forecast
Julian from Lee's Summi: Where will Space Shuttle Atlantis land if there is bad weather at Kennedy?
Ask The Mission Team - Question and Answer Session
Winters: Spaceflight Meteorology Group at Johnson Space Center provides landing weather forecasts to the Flight Director. If landing weather is considered "no-go" at Kennedy Space Center, the Flight Director may decide to land at one of the two alternate sites: Edwards Air Force Base, California or Northrop Strip at White Sands Missile Range in New Mexico. We usually have two to three days of opportunity to land the shuttle, so if the weather is no-go at KSC, the Flight Director can decide to land at an alternate site or wait another day to try again at Kennedy Space Center.
Piet from Haelen, NL: Is it a concern that Tropical Storm Chris is on a course to Florida with a expected arrival on the 7 or 8 of August. Could it could mean a probable return of the space shuttle to the VAB?
Winters: Tropical storm Chris has now come and gone, and it was a concern as it developed and moved into the Eastern Caribbean. Our squadron updated personnel at Kennedy Space Center and I provided daily updates to the Shuttle Launch Director concerning Chris. Luckily, Chris entered an area where the upper level wind sheer was strong, and it could not maintain itself in that environment; therefore, there was no need for NASA to consider rolling Atlantis back from the launch pad.
William from Andover (UK): When Discovery was approaching landing the cloud base seemed very low giving a small landing window, how is the final landing cloud base determined and what options are there available if the base descends very quickly on approach? Secondly, who makes the decisions -- the weather experts, the flight director or the crew?
Winters: Spaceflight Meteorology Group (SMG) at Johnson Space Center determines the weather forecast for landing. To determine the ceiling at the Shuttle Landing Facility, SMG obtains weather information from a weather observer at the Shuttle Landing Facility, who uses laser ceilometers located around the airfield. SMG can also use satellite information and reports from the Shuttle Training Aircraft that flies approaches to provide additional weather information.
The cloud ceiling constraint is 8,000 feet for a shuttle landing, so that if landing aids fail or are degraded, the Shuttle Commander has time to manually adjust for those errors. Otherwise, the shuttle is fully instrumented for landing with lower ceilings.
During Discovery's landing, the ceiling was 11,000 feet -- well above the 8,000 foot constraint -- but after the deorbit burn a shower developed southeast of the airfield. In a case like this, when the weather situation changes after the deorbit burn, the Flight Director obtains reports from SMG and the Shuttle Training Aircraft pilot and consults the flight control team members. The Flight Director ultimately makes the final decision for landing and can change the planned landing approach to the airfield if necessary.
Daryl from Jal: Noticing that weather caused a delay in getting the shuttle stack to the launch pad, how can bad weather affect the shuttle at the pad, and when would you have to consider bringing the stack back to the VAB due to weather?
Robert from Terre Haute: With Atlantis at launch pad 39B, how does NASA plan to protect it from possible severe weather, such as hurricanes?
Jennifer from Green Bay, WI: If a hurricane were to threaten to hit the Cape Canaveral area, what procedures would you go through to keep the shuttle safe from damage? Would it be brought back to the Vehicle Assembly Building or left at the pad?
Winters: Weather can be hazardous here in Florida in the summer. Central Florida is the lightning capital of the United States. Since weather can cause damage to the vehicle and threaten personnel during ground operations such as rollout, weather constraints are clearly defined for these operations. For example, for rollout, there must be a 10 percent or less chance of lightning within 20 nautical miles of the vehicle. Other concerns for shuttle operations are wind, rain, and cold temperatures. The 45th Weather Squadron provides forecasts as well as weather warnings and advisories to protect shuttle operations from hazardous weather.
The shuttle is protected from lightning at the launch pad by a grounded cantenary wire system with a large lightning rod at the top of the Fixed Service Structure, the center structure at the launch pad. If severe weather threatens the area, the shuttle team can extend the Rotating Service Structure around the orbiter to protect it from hail, wind-driven rain, or high winds. Still, the external tank and solid rocket boosters are always exposed and are vulnerable to hail.
As for hurricanes, we watch the tropics closely during the hurricane season. I brief the launch director daily on the threat of tropical systems. If a tropical cyclone becomes a threat to the shuttle, I begin briefing the Kennedy Space Center Hurricane Management team two to three times per day. If we expect the peak winds to reach or exceed 70 knots, NASA plans to roll the shuttle back to the Vehicle Assembly Building. The rollback preparations and actual roll back take about two days depending upon the configuration at the Vehicle Assembly Building and the vehicle at the launch pad.
Ryan from Houston: I noticed during the launch of Discovery that weather gave concerns on the first and second attempts. What happens if the launch was in the final seconds and weather went from green to red?
Winters: If weather threatens the safety of the crew or vehicle, I can call a cutoff down through the final seconds of the countdown. We have well-defined procedures in the event this is necessary.
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