How the weather affects space shuttle launches

March 16, 2:37 PMCleveland Weather ExaminerPaul Fuhr

Previous Next

Comment Print Email RSS Subscribe

Subscribe

Get alerts when there is a new article from the Cleveland Weather Examiner. Read Examiner.com's terms of use.

Email Address   Include other special offers from Examiner.com Terms of Use

7 astronauts left Earth on the Discovery last night

After several delays, the space shuttle Discovery blasted off for the 36th time last evening into a clear sky. While the latest delays were related to mechanical issues, the weather has forever complicated -- if not plagued -- the space shuttle program. In fact, the weather plays such a critical role in each launch that NASA's meteorological team keeps an unusually intense eye on the conditions around the launch pad, producing incredibly careful and detailed forecasts. No less than eight forecasts are made in the 24 hours leading up to launch.
 
Before each launch, NASA gathers data from a mind-boggling number of sources:

- Radar: Launch forecasters use two different types of radar, including the NEXRAD Doppler radar. The NEXRAD radar is able to see rain intensity, wind velocities, and cloud formation out to a distance of 200 nautical miles.
- Field Mill Network: There are 31 field mill sites around each launch area, which help give forecasters information on lightning activity as well as surface electric fields. The sites help determine if there is enough of an electric charge in the air to trigger lightning.
- Lightning Detection System: This system detects cloud-to-ground lightning within 125 nautical miles of the launch site.
- Lightning Detection and Ranging (LDAR): This system sees lightning between clouds and cloud-to-ground in three dimensions.
- National Lightning Detection Network: This system is used to see cloud-to-ground lightning on a national level. It’s necessary to help ensure safe travel of the orbiter upon launch and re-entry.

(Above photo: Lightning strikes the shuttle launch pad on August 25, 2006. Source: NASA)

- Weather Balloons: These balloons, tracked by radar, provide information on temperature, dewpoint, humidity, and wind speeds up to 100,000 feet.
- Doppler Wind Profiler: This measures the upper level wind speeds and directions over the launch area. It receives data every 5 minutes, making sure that the upper winds have not changed.
- Rocketsonde: A rocket-launched instrument that senses and transmits data on temperature, wind speed and direction, as well as air density and pressure.
- Satellite Images: Provided by NOAA weather satellites, the high-resolution images help forecasters see the entire area prior to the launch. 
- Meteorological Interactive Data Display System (MIDDS): Accumulates all of the weather data onto one terminal, providing meteorologists a one-screen glimpse of everything from satellite images to current weather observations.
- Towers: There are 33 meteorological towers around the launch site, including two at each launch pad. Each tower is 60 feet tall and is vital in short-term forecasting.
- Buoys: Weather buoys are anchored 20, 110 and 160 nautical miles out from the launch sites. The buoys provide hourly readings of temperature, wind speed, pressure, sea water temperature, and wave height.
- Weather Reconnaissance Aircraft: A T-38 jet and a Shuttle Training Aircraft is flown to retrieve information.

A shuttle mission is routinely delayed for any of the following reasons:

- Precipitation: Shuttles cannot launch when any precipitation is falling.
- Clouds: Meteorologists analyze the clouds very carefully prior to a launch. If a shuttle passes through or close by a cumulus cloud, it can trigger lightning.
- Wind: A launch cannot take place in winds from the northeast of more than 19 knots, nor in winds from other directions that exceed 34 knots.
- Ceiling: The U.S. Air Force 45th Space Wing must be able to maintain visual contact with the shuttle during liftoff. As such, a ceiling of less than 6,000 feet would cause a launch delay.
- Temperature: While temperatures below 48 Fahrenheit can lead to ice buildups, hot temperatures are typically not a problem for shuttle launches.

From launch to landing, a shuttle mission is a carefully-choreographed dance of science, engineering, and weather. The weather plays an incredibly dramatic part in each launch, routinely presenting unique problems and challenges to the thousands of NASA personnel trying to send astronauts into space. Each launch is almost as unpredictable as the weather itself: an ever-changing series of variables that must align perfectly.