Spaceflight Now: STS-92 Mission Report

NASA faces bad weather at both landing sites today
BY WILLIAM HARWOOD
SPACEFLIGHT NOW

Posted: October 23, 2000

  Wind sock
The wind sock at Kennedy Space Center's Shuttle Landing Facility illustrates the high crosswind on Sunday. Photo: NASA TV/Spaceflight Now
 
The Discovery astronauts are gearing up to make a second landing attempt today, but forecasters say the weather remains unfavorable, with high crosswinds and low clouds at the Kennedy Space Center and possible rain showers at Edwards Air Force Base, Calif.

Commander Brian Duffy and his crewmates have up to five landing opportunities on four successive orbits today - two in Florida and three in California - with the first on tap at 2:51 p.m. at the Kennedy Space Center and the last at 7:35 p.m. EDT at Edwards.

The latest Kennedy Space Center forecast from the Spaceflight Meteorology Group at the Johnson Space Center calls for winds out of the northeast - almost a pure crosswind - at 15 knots with gusts up to 25 knots and a chance for a broken deck of clouds at 4,000 feet.

NASA's daylight end-of-mission crosswind limit is 15 knots and any broken decks of clouds must be above 8,000 feet.

At Edwards in California's Mojave Desert, winds will be out of 50 degrees at six knots gusting to 10 knots with a broken cloud deck at 7,000 feet and a chance of rain showers within 30 miles of the runway. Expected flight rule violations are low ceilings and rain.

The forecast for a Tuesday landing attempt at Kennedy remains much the same, but Edwards improves dramatically, with no expected flight rule violations.

"The forecast for Edwards is quite good for Tuesday," said entry flight director Leroy Cain.

But NASA wants to get Discovery back on the ground in Florida if at all possible to minimize delays readying th ship for its next flight Feb. 15 to carry a fresh crew to the international space station and to bring the lab's first full-time crew back to Earth.

A landing at Edwards would add 10 days or more to Discovery's ground turn-around and cost NASA some $1 million.

Hoping for the best, Discovery's crew began working through the entry day timeline shortly after wakeup at 6:17 a.m., setting their sights on a 2:51 p.m. landing on runway 33 at the Kennedy Space Center. Here's the flight plan:

TIME.......EVENT

06:17 AM...Crew wakeup
07:17 AM...Supply/waste water dump
08:37 AM...Laptop computer teardown
08:47 AM...Group B flight computer powerup
08:47 AM...Printer stow
08:52 AM...Maneuver to navigation alignment
	attitude
09:17 AM...Inertial measurement unit alignment
09:46 AM...Deorbit timeline begins
11:03 AM...Payload bay doors closed
11:26 AM...Computers loaded with entry software
12:21 PM...Astronauts begin donning pressure suits
01:26 PM...Mission control 'go' for deorbit burn
01:43 PM...Deorbit ignition
01:46 PM...Deorbit burn complete
02:20 AM...Entry interface
02:24 PM...77-degree right roll
02:32 PM...60-degree right roll
02:45 PM...Velocity less than mach 2.5
02:47 PM...Velocity less than mach 1
02:47 PM...Shuttle on the runway heading
	alignment cylinder
02:51 PM...Landing

For shuttle launches, which always includes the possibility of an emergency landing back at the Kennedy Space Center, the crosswind limit can be slightly higher than 15 knots.

But for end-of-mission landings, when the pilots have been in weightlessness for more than a week and haven't had a chance to practice since before launch, the limit is a strict 15 knots. The end-of-mission limit for night landings is 12 knots.

"The rules for daylight landings is 15 knots on the crosswind and there are a number of reasons why the rule is what it is," said Cain.

"Part of the rationale is the deconditioning aspect that's a variable for us with the crew being on orbit for 10 or 12 or more days. The controllability of the vehicle in the crosswind, with our experience base and all the simulation and test data we have, suggests that's a good number."

The crew's initial landing try Sunday was called off when afternoon crosswinds gusted to some 20 knots. Conditions are expected to be slightly worse today.

"The winds are expected to be as strong or stronger than they were (Sunday)," Cain said. "With respect to Edwards, we're expecting a chance for some ceilings there as well as a potential chance for some rain showers in the area."

The shuttle has enough fuel, electrical power and carbon dioxide absorbent to remain in orbit until Wednesday in a worst-case scenario.

But the outlook for Edwards improves Tuesday and it's unlikely NASA would keep the crew up until Wednesday unless the forecast for Kennedy improved dramatically.

Ground track
See the path Discovery would follow during landing opportunities today in our STS-92 Landing Tracker.

KSC Orbit 185 - touchdown in Florida at 1851 GMT.

EAFB Orbit 186 - touchdown in California at 2023 GMT.

KSC Orbit 186 - touchdown in Florida at 2028 GMT.

EAFB Orbit 187 - touchdown in California at 2158 GMT.


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