Weather forecast remains poor for Discovery launch
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: December 8, 2006
Shuttle weather officers are continuing to predict a 70 percent chance of bad weather for Saturday's attempt to launch Discovery on a space station assembly mission. "High pressure is migrating into the Eastern US, increasing the pressure gradient over Central Florida; therefore, cool, windy conditions will affect Kennedy Space Center (KSC) Friday," according to the official forecast. "By Saturday, winds will gradually decrease as the high pressure area migrates east, but Shuttle Landing Facility (SLF) crosswinds worsen as the winds continue to turn northeast.
"Also, the easterly flow causes concern for low clouds and isolated showers. Our primary concerns for launch day are SLF crosswinds, a low cloud ceiling, and isolated showers."
The Spaceflight Meteorology Group at the Johnson Space Center in Houston predicts scattered clouds at 3,000 and 20,000 feet with a chance for broken clouds at 3,000 feet and showers within 20 nautical miles - both violations of NASA's flight safety rules. Winds will be out of 40 degrees at 12 knots gusting to 18, translating into a 16-knot crosswind - another violation - on the shuttle's emergency runway.
Hoping for the best, engineers plan to top off on-board supplies of liquid hydrogen for Discovery's fuel cells tonight. That will permit launch tries Saturday and Sunday before a standown Monday to top off liquid oxygen. Additional attempts will be possible Tuesday, Thursday and Saturday, Dec. 16.
Dec. 17 is the end of the currently approved launch window. If Discovery is launched on or before Dec. 17, it can complete its 12-day mission and land before the end of the year, even if up to two contingency days are needed because of bad weather or other problems.
Based on the space station's orbit, the window extends through Dec. 26 but any launch past Dec. 17 would require NASA managers to approve flying Discovery over the new year transition. The shuttle's flight software was not designed for use during year-end rollovers and some internal clocks would consider Jan. 1 to be day 366 instead of the first day of a new year.
While the astronauts can reset the computers in flight, managers likely would want the shuttle docked with the international space station on New Year's day just to be safe. That requirement would rule out launches between Dec. 18 and 22.