The Spaceflight Meteorology Group

Postflight Mission Summary for STS-84

June 3, 1997

Atlantis Tests New Flight Rule Limits

The Space Shuttle Atlantis touched down at the Kennedy Space Center (KSC) in Florida at 1328 UTC on Saturday May 24 after nine days in space, five of those docked with Russian Mir Space Station. NASA exchanged Mike Foale for Jerry Linenger who had been aboard Mir for 4 months.

Atlantis lifted off on time at 0807 UTC on May 15 under clear Florida skies and ideal launch weather conditions. The landing weather on May 24, however, was quite another story.

A weak dissipating frontal trough provided thick cloud cover over most of peninsular Florida 6 hours prior to scheduled touchdown. As a result, the decision to deorbit was postponed one orbit later, and nearly for 24 hours. NASA just recently lowered the KSC End of Mission ceiling flight rule limits from 10,000 to 8,000 feet effective for STS-84. As fate would have it, the limits got a real test as Atlantis landed with a broken ceiling of 8,500 feet.

The decision to wave-off the 1st opportunity (1151 UTC) was made at 1015 UTC, when cloud ceilings surrounding the Shuttle Landing Facility (SLF) were below flight rule limits even though significant drying was occurring to the north. This proved to be a wise decision as the verifying observation for the 1st opportunity carried a ceiling of 7,000 ft.

The decision for the 2nd landing opportunity was even tougher as lower clouds began to develop when the convective temperature (77) was reached two hours before scheduled 1328 UTC touchdown. The forecast was amended 20 minutes prior to deorbit decision from a “GO” to a "NO GO" due to the threat of low ceilings. However, ten minutes later, conditions began to improve at the SLF, and with the help of the Shuttle Training Aircraft (STA) weather reconnaissance, forecasters were able to remove the mention of low ceilings from the forecast just two minutes prior to the final deorbit burn decision. The observed ceiling at touchdown was 8,500 broken, although ceilings at 7,500 broken were observed briefly, both prior to and during deorbit, by the SLF observer and the STA weather aircraft.

Melbourne WSR-88D in clear air mode and GOES 8 band 2 IR were valuable tools in detecting and evaluating cloud development and movement during these shuttle landing decisions. Also the "Nite Fog" enhancement which utilizes the differing band widths from 10.7 to 3.9 microns was useful earlier in the evaluation process when the cloud layers were lower.

STS-84 marked the 8th consecutive KSC landing, a new record for the Space Shuttle program. SMG Lead forecaster for STS-84 was Wayne Baggett working his 7th mission as Lead and 43rd mission overall. Dan Bellue was the Assistant Lead/TAL Forecaster, while Doris Rotzoll was the Lead Techniques Development Meteorologist.

Submitted by:

Wayne Baggett - STS-84 Lead Forecaster