Crucial Forecasts for Space Shuttle Missions

Crucial forecasts for space shuttle missions are made by the Spaceflight Meteorology Group in Houston, Texas. These forecasts are provided to the Flight Director for RTLS (Return-to-Launch Site) at Kennedy Space Center (KSC), TALS (Transoceanic-Abort Landing Sites), AOA (Abort Once Around) and EOM (End of Mission . . . at KSC or Edwards AFB, California). The shuttle has very restrictive weather flight rules dealing with ceilings, visibilities, winds, and precipitation.

The Return to Flight of the Space Shuttle Discovery in September 1988, STS-26, had some challenging weather moments, particularly on launch day. The TAL sites in Spain and Morocco had precipitation and crosswind problems. The RTLS site in Florida was plagued by increasing rainshowers. Crucial weather forecasts and monitoring continued through the final tense moments before launch.

The Atlantis Mission in October 1989, STS-34, had weather problems on both launch and landing days. An amended forecast for thunderstorms caused a last minute scrub on the original launch day. The next day rainshowers in Florida cleared to allow a launch. The Atlantis was brought home two orbits early due to forecast high winds at Edwards AFB, California. However, visibilities as low as one-sixteenth of a mile occurred within an hour of the deorbit burn. The fog cleared in the minutes before the final decision to land was made.

Hours before the scheduled launch of STS-40 on June 5, a mesoscale convective complex bore down on Cape Canaveral from the north. Fortunately, skies cleared enough to launch with only 30 minutes remaining in the launch window.

Weather forecasting was extremely challenging for the September 1994 mission of the Space Shuttle Discovery. The lead forecaster and the SMG team were honored by being selected to "Hang the Plaque" in Mission control immediately following the STS-64 landing. This award is made to the flight control team which provided outstanding support to the just-completed Shuttle mission.

Discovery launched on September 9, 1994, at 2223 GMT. After a tense 2 hour and 23 minute hold for thunderstorms, SMG advised the NASA Flight Director that RTLS weather would be acceptable IF the launch occurred immediately. Based on SMG's "go now" recommendation to the Flight Director and his recommendation to the KSC Launch Director, the countdown clock came out of the 5-minute hold, and the Shuttle launched at 2223 GMT, 37 minutes before the launch window closed.

Clouds, showers, and thunderstorms forced a waveoff of all KSC landing opportunities on September 19th and 20th. An intense effort was made to find a "hole" in the weather in Florida. However, conditions were unstable and remained unacceptable to meet the strict weather flight rules for landing. Discovery landed at Edwards AFB, California, September 20, at 2113 GMT. Mostly sunny skies with scattered low clouds greeted the STS-64 astronauts after their successful 11 day mission.