Weather plays a major role in determining
whether an end-of-mission landing is at KSC or at Edwards Air Force Base, or is postponed
until a later orbit.
The following weather constraints apply to
KSC:
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At the time of
the deorbit burn go/no-go decision, which occurs approximately 90 minutes prior to
landing, observed cloud cover below 8,000 feet (2438 meters) should not exceed 25%
coverage and must be forecast not to exceed 50% at landing time. |
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Also, observed visibility at
deorbit burn should be and the forecast visibility for landing time must be 5 statute
miles (8043 meters) or greater. |
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Crosswinds must
not be greater than 15 knots or 15 nautical miles per hour (17 statute miles/28 kilometers
per hour) if it is a daytime landing, and 12 knots or 12 nautical miles per hour (14
statute miles/22 kilometers per hour) if it is a nighttime landing. In more restrictive
landings — because of weight or mission duration, for example — crosswinds must
not exceed 12 knots or 12 nautical miles per hour (14 statute miles/22 kilometers per
hour). |
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Thunderstorms
within 30 nautical miles (34.5 statute miles/56 kilometers) and/or rain within 30 nautical
miles (34.5 statute miles/56 kilometers) also are landing constraints. |
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Wind direction
usually will be the key factor in determining the final approach to the runway. The sun
angle, if it is in the pilot’s field of view, is also considered. Under normal
circumstances, the orbiter will land into the wind. If the wind direction is from the
south, the final approach will be from the north; if the wind direction is from the north,
the orbiter will approach from the south. |
Pre-landing weather forecasts
are issued by the Spaceflight Meteorology Group at Johnson Space Center, Houston, Texas.
The group is part of the National Weather Service and works closely in coordinating its
forecasts with Range Weather Operations at Cape Canaveral Air Force Station (CCAFS).
Weather instrumentation at KSC and at the adjacent CCAFS provide some of the data that the
Spaceflight Meteorology Group uses in preparing its landing forecast. Weather conditions
also are evaluated by NASA astronauts piloting reconnaissance aircraft along the
orbiter’s landing approach before the orbiter is committed to re-entry. |
