The Spaceflight Meteorology Group

Postflight Mission Summary for STS-79

October 18, 1996

...New shuttle flight duration record...

Space Shuttle Atlantis landed at the Shuttle Landing Facility (SLF), Florida at 12:13 UTC, September 26,1996, after the six person crew successfully completed their ten day historic mission and returned Astronaut Shannon Lucid to Earth after her six month record-breaking spaceflight.

Weather for launch day proved to be exciting. Within the last two hours of the launch count, surface observations at both the SLF and at Zaragoza violated the weather flight rules briefly. A low cloud deck at 9 hundred feet developed a ceiling at Zaragoza. This deck rapidly burned off before launch. However, for a period in the launch count the prime TAL site was observed "NO GO". Rain showers off the east coast of Florida moved north northwestward just west of the SLF causing a "NO GO" observation within the last hour of the count. These showers continued to move north northwestward and began dissipating, so that no delay in the count was incurred. SMG forecasts for all sites remained "GO" through the count, and Atlantis lifted off at the beginning of the "5 minute" window at 08:54:48 UTC for an "on-time" launch.

The very short launch window was necessary to insert Atlantis into proper orbit to accomplish the docking with the MIR Space Station, retrieve Astronaut Shannon Lucid, and deploy Astronaut John Blaha for his extended flight in MIR. Secondary mission objectives were also met successfully.

An apparent failure of an Auxiliary Power Unit (APU) caused concern to flight controllers and mission managers. It also made the landing flight rules more restrictive, i.e, by lessening the crosswind limit from 15 knots to 10 knots allowed for landing. On-orbit support consisted of daily Mission Management Team (MMT) weather briefings. Five days before the planned landing, SMG briefed detailed forecasts for landing day and for the following two days' landing opportunities. Atlantis did have enough consumables on board to remain on orbit until Sunday, September 29th, if necessary. However with the apparent failed APU, mission managers decided to take the earliest opportunity to land at the site (either Florida or California) with the most favorable weather.

Touchdown of Atlantis occurred at the Shuttle Landing Facility (SLF), KSC, Florida at 1213 UTC, September 26, after ten days in orbit. On landing day, winds at the surface and in the low level remained east southeasterly as high pressure over the eastern U.S. dominated weather in Florida. Normally in deep easterly flow over Florida, rainshowers and low cloud ceilings develop over the water and advect across the Cape. This occurred to some extent. However, a strong subsidence inversion aloft and brisk winds aloft prevented cloud growth above about 8 000 feet. The SMG forecasters used enhanced IR satellite imagery to identify and track low cloud elements which were confirmed by the Shuttle Training Aircraft (STA) and the WSR- 88D at Melbourne. An anxious moment for SMG forecasters occurred when the STA pilot announced just a few minutes before the deorbit burn that low clouds over the water approximately 25 miles offshore were moving toward the Cape. SMG forecasters held to a "GO" forecast, and Atlantis touched down without incident. Weather remained favorable through post landing operations.

Lead Meteorologist for STS-79 was Dan Bellue. Tim Garner was the Assistant Lead, and Mark Keehn worked as the Lead Techniques Development Unit (TDU) Meteorologist. This marked the third time that these meteorologists together have worked a shuttle launch and landing.

Submitted by: Dan G. Bellue