The Spaceflight Meteorology Group

Postflight Mission Summary for STS-81

March 3, 1997

...Fifth Shuttle-Mir Docking Mission...

The Space Shuttle Atlantis landed at Florida's Kennedy Space Center (KSC) Shuttle Landing Facility (SLF) at 1423 UTC [9:23 AM EST] on Wednesday, January 22, 1997 after a 10 day mission. Atlantis had launched from KSC's Pad 39B on Sunday, January 12th, at 0927 UTC (4:27 AM EST). The main objective of this mission was to dock with Mir, off-load supplies and experiments, exchange US astronaut Jerry Linenger for John Blaha, and return equipment and experiments from the Mir space station. John had spent almost four months on Mir when Atlantis lifted off. Prior to undocking almost four tons of water, supplies, and experiments had been exchanged, in addition to the two astronauts. NASA managers consider STS-81 a fully successful mission.

For launch, the return to launch site forecast for KSC called for scattered low clouds and patchy shallow ground fog. High pressure covered the southeastern US and there was a weak east-west stationary front over central Florida, south of KSC. Surface winds at KSC were light north to northwest, and westerly aloft. Due to abundant low level moisture there were minor concerns early in the launch count that the low clouds might becoming broken or that the shallow fog might thicken and reduce visibility. Sounding balloons and reconnaissance reports dispelled concerns about the clouds. Patchy ground fog was being reported in the surface observations, but winds just above the surface were strong enough to preclude widespread fog. High pressure also covered the three overseas abort landing sites. Less than thirty minutes prior to launch, low clouds were detected approaching the runway at Zaragosa. The forecast was amended to "NO GO" for a low cloud deck and the prime overseas abort site was changed from Zaragosa to Moron.

For landing day, high pressure over the western Atlantic ridged southwest over the Florida peninsula. Low level winds were southeasterly. The forecast for the first landing opportunity at KSC called for broken low clouds - "NO GO". Low ceilings were evident on satellite imagery over the water and cloud level winds were southeasterly, bringing clouds in from off-shore. Through the landing count, balloon soundings indicated no change to the saturation or to the wind direction at the cloud level. Surface observations at the SLF went from broken to scattered three hours before landing and remained scattered until the first de-orbit decision point. However, with no clear and convincing evidence that the clouds would stay scattered through landing, the forecast was held at broken - "NO GO". The NASA Flight Director at Mission Control waved-off the first opportunity. The low clouds went broken immediately following that decision and then became scattered, again. For the second opportunity, the balloon soundings indicated drying at the cloud level with only minor veering of the winds. The low clouds remained scattered. Visible satellite imagery became available, yielding better resolution of cloud groups, directions, and speeds and the forecast was amended to "GO". The Flight Director gave the crew was given a "GO" to de-orbit and landed a little over an hour later under almost clear skies.

Lead Meteorologist for STS-81 was Karl A. Silverman, working his 19th mission, third as Lead. Steve Sokol was Assistant Lead, and Doris Rotzoll worked as the Lead Techniques Development Unit (TDU) Meteorologist.

Submitted by:

Karl A. Silverman February 5, 1997