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Postflight Mission Summary for STS-106

September 29, 2000

The Space Shuttle Atlantis and its seven member crew touched down in Florida at 0756 UTC on Wednesday, September 20th. This was the 23rd consecutive landing at the Kennedy Space Center (KSC) and the 15th nighttime landing in shuttle history. While in orbit, the STS-106 crew successfully prepared the International Space Station for the arrival of the first permanent crew. The five astronauts and two cosmonauts also delivered more than 6,600 pounds of supplies and installed batteries, power converters, a toilet and a treadmill on the station. Two members of the crew also performed a space walk to connect power, data and communications cables to the newly arrived Zvezda Service Module and the station. This successful 12 day mission marked the completion of the 99th shuttle mission. Extensive coverage of STS-106 can be found at: http://www.spaceflight.nasa.gov/shuttle/archives/sts-106/index.html

Weather played a major role in the decision making process for both the launch and the landing.

Early in the launch count, scattered rain showers covered the KSC area, violating the 'no precipitation within 20 NM' weather flight rule. The showers were expected to diminish but not dissipate through the count. The Return To Launch Site (RTLS) abort landing forecast included showers within 20 NM. Weather flight rules for RTLS allows for isolated light rain showers to exist, providing certain criteria are met. There is also an exception in this rule which can be invoked in very specific circumstances when there are moderate showers involved. A second concern for RTLS was thunderstorms approaching from the northeast. Forecast movement of the anvils would bring them over the KSC complex at abort landing time, another weather flight rule violation. The final concern was shower development along outflow boundaries within the 20 NM exclusion zone.

At launch minus four and a half hours, SMG briefed the astronaut crew and flight control team, including the ascent flight director, about these issues. There were no weather concerns at the overseas abort sites in Spain or Morocco.

The showers continued to diminish as launch time approached. The speed of the approaching thunderstorms slowed enough to remove the threat of anvils violating weather flight rules. Outflow boundary showers that had been developing ahead of the approaching thunderstorms became less frequent and weaker in strength as the storms approached. Applying the exception portion of the RTLS rain shower flight rule to the existing and potential showers allowed for an on-time launch at 1245 UTC, the opening of a two and a half minute launch window.

Weather concerns for landing on September 20th were also challenging. Hurricane Gordon had dropped 2 to 3 inches of rain on the KSC complex a few days before landing, and Tropical Depression #12 regenerated over Cuba the evening before the landing. Also, due to a satellite eclipse, there would be no GOES East satellite imagery during a critical portion of the landing count, from touchdown minus 4 hours (TD-4 hrs.) to TD-1 hr (just after the de-orbit burn). Weather flight rules for landing are more restrictive than for launch. There can be no thunderstorms, including electrified anvils, or showers within a 30 NM radius of the runway. Radar and weather reconnaissance aircraft reports would be especially critical.

When the Spaceflight Meteorology Group entry team relieved the planning team at touchdown minus 9 hours (TD-9 hrs), showers were occurring along the east coast of Florida and thunderstorms were over western and southern Florida. SMG predicted that the thunderstorms would diminish but maintained "showers within 30 NM" in the landing forecast.

At TD-4 hrs. (de-orbit burn minus 3 hrs.), the flight control team, including the entry flight director, was given a thorough weather briefing. The thunderstorm activity that could effect KSC had been decreasing, but anvils would continue to move towards KSC. The shower activity had also been decreasing in intensity and areal coverage. The downward trend in both thunderstorm and shower activity was expected to continue but neither concern could yet be eliminated.

At de-orbit burn minus 1 hour, with weather recon reports confirming what the radar was indicating, the flight director was informed that the anvils would no longer be a threat. The only remaining concern was the shower activity, which continued to diminish.

At TD-1:30, less than a half hour before the de-orbit burn, the showers were removed from the forecast. With no showers in the forecast, the forecast was then 'go' based on the weather flight rules. At TD-1:20, the flight director gave the crew a 'go' for the de- orbit burn. Five minutes later, the weather recon aircraft reported low clouds developing near the landing runway. The astronaut pilot in the weather recon aircraft was concerned that low clouds could block the visual landing aids. SMG briefed the flight director and entry team that low clouds were expected and in the forecast. This information was relayed back to the weather recon aircraft. The de-orbit burn began at TD-1:07. A little more than an hour later the Space Shuttle Atlantis touched down on runway 15 at KSC. At touchdown, KSC reported a few low clouds, broken high clouds, and no precipitation within 30 NM.

For additional information about the Spaceflight Meteorology Group, shuttle weather forecasts and landing weather requirements, please visit: www.srh.noaa.gov/smg

Lead Forecaster for STS-106 was Karl A. Silverman working his 36th mission, 6th as Lead. TAL Forecaster was Richard A. Lafosse and Lead Technique Development meteorologist was Doris A. Rotzoll.

Submitted by:

Karl A. Silverman

STS-106 Lead Metorologist



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