NASA - National Aeronautics and Space Administration

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I'm George Diller at the Kennedy Space Center in Florida. You need just the right weather to launch a Space Shuttle. Weather an airplane can fly in may not be good enough to launch the space shuttle. Wind, rain and even clouds can stop a countdown.

Space Shuttle Weather Officer Kathy Winters forecasts the weather for a shuttle launch. She stopped by the NASA Direct studios recently to explain what aspects of the weather NASA looks out for.

I'm Kathy Winters. I work at Cape Canaveral Air Force Station. I work for the 45th Space Wing, and I'm the Space Shuttle Discovery's launch weather officer. The shuttle launch weather criteria mainly is focused on natural and triggered lightning, and also some concerns for wind, rain, ceilings in the area and temperatures.

For the natural and triggered lightning, we're mainly looking at any weather that's within 10 nautical miles of the launch pad. We're looking at the clouds, we're looking at the bases of the clouds, the tops of the clouds, because we can actually trigger a lightning strike with a launch. And so we will look at the weather to determine if we are in a situation where that could occur, and we'll evaluate our rules and if we need to go red on those rules, we will, to avoid triggering a lightning strike. We're also concerned about wind at the launch pad, because wind can affect the vent arm that -- those come off of the external tank, the vent arms -- and also the stress on the solid rocket boosters after the shuttle engines light.

Once the shuttle engines light, the wind can cause too much stress on the solid rocket boosters. So wind, any wind exceeding 19 knots, we'll have to evaluate the direction. And finally, temperatures are a concern mainly when we start fueling the vehicle, we start fueling the external tank, we don't want temperatures exceeding 99 degrees Fahrenheit, and cold temperatures, once they get below 48 degrees Fahrenheit, we'll have evaluate the relative humidity and the wind to determine if that's going to be a violation, as well.

One of our concerns for weather at launch is for imaging the launch vehicle. Of course, right now we'd like to get some really good pictures of the shuttle as it's launching and going through solid rocket booster separation and external tank separation. So one of the Columbia Accident Investigation Board's recommendations was to have three usable views of the launch through solid rocket booster separation from the cameras that are on the ground and also in the air.

So we do look at the clouds in that case.
We watch the clouds that are in the area and we compare them to the area that the cameras will be focused in on, and with that information, I provide the launch director information on how the clouds may affect the imaging of the launch vehicle all the way through solid rocket booster separation.

Finally, there is concerns for the landing weather, as well, at the Shuttle Landing Facility. We want to make sure we can land there if we have to abort. And there is concerns there for wind. We don't want to exceed 15 knots of crosswind. We don't want to exceed a 25-knot head wind, or a 10-knot sustained tailwind or 15-knot peak tailwind. And we don't want any showers or storms within 20 nautical miles of the landing site, as well.

Launch day is a great day. We have crew rest. Coming up to launch, we get a good, good night's rest the night before launch, come in very excited to, to start getting into the countdown, and we've, usually when I walk in the door, we've already started fueling the vehicle. We're looking at the solid rocket booster recovery weather. We're looking at the launch weather and we are evaluating the launch constraints. And it's a very nice pace; the days before launch are very, can be very hectic.

As we come into launch day, it's real exciting. We get real focused. So we're actually finally evaluating the weather, and so that's why it's a good day.

You've been listening to NASA Direct.

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