SR SSD 2001-11

Technical Attachment

Shuttle Support Operations by the Spaceflight Meteorology Group

The last two months have been busy at the SMG as shuttle flights in conjunction with building the International Space Station are continuing at a rapid pace. Here is a summary of activities.

STS-98, the 102nd Shuttle mission, lifted-off from Pad 39-A of the Kennedy Space Center (KSC), on February 8, at 23:13 UTC (5:13 PM CST). The shuttle Atlantis was launched into a 51.6 degrees orbit inclination at an altitude of 199 mi. The prime Transoceanic Abort Landing (TAL) site was Ben Guerir, Morocco. The weather alternate TAL site was Zaragoza, Spain. Low ceilings and precipitation within 20 nm precluded the use of Moron, Spain as a TAL weather alternate. The shuttle remained in orbit for almost 13 days while the shuttle crew delivered and installed the U.S. Destiny Laboratory to the International Space Station (IBS).

The launch weather in Florida was rather benign as high pressure dominated weather patterns for launch day. Weather at the TAL sites was a different story. An upper level low with bands of cloudiness and showers threatened the northern TAL sites. Ceilings and the threat of precipitation caused concerns at Moron. Precipitation and surface winds were a possible limiting factor at Zaragoza.

Landing Weather: A cold front pushed through the Florida peninsula Saturday and high pressure over the eastern U.S. influenced weather over the eastern portion of the nation. Out west a trough began moving onshore in southern California on Monday and influenced weather at Edwards AFB Monday and Tuesday.

February 18, Forecasts of excess crosswinds at the KSC Shuttle Landing Facility caused a 24 hr wave-off for STS-98 crew.

February 19, Excess crosswinds at KSC and low ceilings and precipitation in California caused another 24 hr wave-off.

February 20, Low ceilings at KSC caused a delay in closing the Shuttle payload bay doors until the second KSC landing opportunity of the day. Forecasts of cloud ceilings and precipitation for this second KSC opportunity required a wave-off to Edwards AFB. The first Edwards opportunity was the only good opportunity for the day because low cloud ceilings and crosswinds for the second opportunity were forecast to be out of landing limits. Atlantis landed at Edwards at 20:33:06 UTC (2:33:06 PM CST).

Other mission information is available at SMG's Web site at or from NASA sites at and

SMG lead meteorologist Dan Bellue worked his 92nd mission (17th as lead). Wayne Baggett was the assistant lead and Doris Rotzoll was the techniques development unit meteorologist.

STS-102, the 103rd Shuttle mission, lifted-off from Pad 39B at KSC on March 8 at 1142 UTC. Discovery was launched to an altitude of 173 nm. Discovery remained in orbit for almost 13 days while the crew delivered and installed the Leonardo cargo module and performed the first crew exchange to the ISS.

Launch Weather: High pressure over the Southeast provided clear skies and light winds at the Shuttle landing facility in the early pre-dawn hours on Thursday, March 8. Temperatures in the 40s, however, caused some concern for forecasters at the 45th Weather Squadron dealing with Launch Commit Criteria (LCC). With winds at the 60 ft level on the launch pad at 8-12 kt and relative humidity near 75 percent, the temperature constraints governing LCC remained within limits during the launch count. Pad temperature at lift-off was 44.

Weather at Zaragosa and Moron in Spain proved more troublesome due to a strong low pressure system approaching the British Isles and another system well offshore. The prime Transoceanic Abort Landing (TAL) site was Ben Guerir, Morocco. Low ceilings and precipitation within 20 nm precluded the use of Moron, Spain as a TAL alternate. Crosswind concerns reduced Zaragosa, Spain from a TAL option the status of an Augmented Contingency Landing Site (ACLS). Fog formed at Ben Guerir, late in the launch count, but visibilities improved about 40 minutes prior to launch providing acceptable weather there. As a result, Discovery launched on time at 11:42 GMT.

Landing Weather: An intense low pressure system over south Alabama threatened to delay the landing of Discovery on the night of March 20. Strong crosswinds, bands of low clouds and rainshowers approaching from the west resulted in a "NO GO" forecast and a wave-off of the first KSC landing opportunity. By the time of the second opportunity de-orbit decision, conditions had improved significantly, resulting in a "GO" forecast and a decision to de-orbit to KSC. Winds, however, began increasing shortly after the de-orbit burn and at touchdown were reported at 9 kt with 10 minute peaks to 16 kt. Discovery coasted to a smooth landing at 0731 UTC. One-second post-landing wind data revealed winds averaged just under 10 kt from main gear touchdown until wheelstop, so winds did not exceed the 12 kt limit during this landing period.

Other mission information is available at the SMG Web site under the link for the Spaceflight Meteorology Group (SMG) at, or from NASA Public Affairs Office at Web page or

SMG lead meteorologist Wayne Baggett worked his tenth mission as lead. Karl Silverman was the assistant lead and Mark Keehn was the lead techniques development unit meteorologist.

STS-100, the 104th Shuttle mission, is scheduled to lift-off from Pad 39A at KSC on April 19, at 1912 UTC. The launch window will last only about five minutes and Endeavor will be launched to an altitude of 199 mi. The prime Transoceanic Abort Landing (TAL) site will be Zaragoza, Spain and the weather alternate TAL sites will be Moron, Spain and Ben Guerir, Morocco. This will be the ninth Shuttle mission in support of the assembly of the ISS.

Climatologically, the greatest threat of weather impacting a Return To Launch Site (RTLS) abort landing is crosswinds. For the launch to occur, the RTLS forecast, valid 25 minutes after launch, must be "Go." The biggest threats at the three TAL sites are low ceilings and low visibilities. Crosswinds are also a concern. For launch, at least one TAL site must be "Go."

Endeavor will remain in orbit for 11 days. While docked with the ISS, supplies and experiments will be transferred using the Italian made Multi-Purpose Logistics Module, also known as Raffaello. An ultra high frequency (UHF) antenna and Space Station Remote Manipulator System (SSRMS) will also be placed on the station. Two spacewalks are planned to install the space station robotic arm, the antenna and carry out other assembly tasks.

The landing is scheduled for 1510 UTC (10:10 AM CDT), on April 30, back at KSC. The alternate landing site is Edwards AFB in California. Up-to-date launch and landing times and forecasts (beginning two days prior to launch) may be obtained via the Internet at the sites indicated above.

SMG lead meteorologist, Karl A. Silverman will be working his 42nd mission, seventh as lead meteorologist. Richard A. Lafosse will be the assistant lead and TAL forecaster. Tim Oram will oversee weather-computing systems as the techniques development unit meteorologist.