Shuttle Discovery will land Friday at one of three sites
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: December 21, 2006
The Discovery astonauts tested the shuttle's re-entry systems today and packed up for a trip back to Earth Friday to close out a successful space station re-wiring mission. Results from a final heat shield inspection, carried out Wednesday, show Discovery's nose cap and wing leading edge panels are in good shape and the crew has official clearance to press ahead with re-entry. The only question is where the seven astronauts will land.
Because of an earlier decision to add a spacewalk to Discovery's mission, the shuttle only has enough supplies to remain in orbit until Saturday at the latest. To provide a safety cushion in case of unexpected problems with the spacecrat, NASA flight rules call for a return to Earth Friday, weather permitting, at one of the agency's three landing sites - the Kennedy Space Center in Florida, Edwards Air Force Base, Calif., or Northrup Strip at White Sands Space Harbor, N.M.
With marginal to bad weather expected in Florida and California, NASA may be facing its first New Mexico shuttle landing since 1982. Because White Sands is NASA's lowest-priority landing site, equipment needed to prepare the shuttle for a ferry flight back to Florida is not readily available and Discovery's return to Kennedy would be delayed up to two months.
That would throw a wrench into NASA's overall processing schedule and likely delay Discovery's next flight in October. But from a crew safety standpoint, "landing at White Sands is of no concern to us at all," said John Shannon, chairman of NASA's Mission Management Team. "The crew gets the bulk of their training in the shuttle trainer aircraft at White Sands."
The hard-packed gypsum runway is level to one inch every 1,000 feet and measures 17,000 feet long and 300 feet wide.
Just in case, two C-17 cargo jets were called up to ferry backup equipment from Kennedy to White Sands, including a purge unit to pump nitrogen gas through the shuttle's plumbing and a power system to run various heaters and other systems to defend against expected freezing weather Saturday night. Rocket nozzle covers also are being sent to keep out gypsum dust, which caused major contamination problems after Columbia landed at White Sands in 1982.
"If we land there, I feel like we're going to be in great shape on the vehicle but the turnaround is going to take a little bit longer," Shannon said. "I would not be surprised if we were out at White Sands for 45 to 60 days."
He said a team of 50 to 60 Kennedy Space Center engineers and technicians are being dispatched to New Mexico to support a possible landing. If Discovery does, in fact, land there, several hundred more workers will fly out the day after Christmas.
Shannon and company are hoping the forecast changes and that the weather will permit a landing in either Florida or California. The astronauts have landing opportunities at all three sites on four successive orbits Friday starting with a deorbit burn on orbit 203 at 2:49 p.m. for a landing on KSC runway 15 at 3:56 p.m.
Edwards, Northrup and Kennedy are available on the next orbit, for landings around 5:30 p.m. EST, and two more opportunities, at Edwards and White Sands, are available the orbit after that around 7 p.m. EST. A final Edwards opportunity is available one orbit later, around 8:36 p.m. EST. But That opportunity would only be available if entry flight director Norm Knight calls off the first Kennedy oppotunity well in advance.
Ground track charts available here.
Entry data available here.
Here are all the landing opportunities for Friday (in EST):
02:49 PM...12...18...02...Orbit 203 deorbit burn (TIG) for KSC landing 03:56 PM...12...19...09...202 KSC landing 04:19 PM...12...19...32...203 Edwards Air Force Base TIG 05:27 PM...12...20...40...EAFB landing 04:20 PM...12...19...33...203 Northrup Strip TIG 05:27 PM...12...20...40...Northrup landing 04:26 PM...12...19...39...203 KSC TIG 05:32 PM...12...20...45...KSC landing 05:54 PM...12...21...07...204 EAFB TIG 07:00 PM...12...22...13...EAFB landing 05:57 PM...12...21...10...204 Northrup TIG 07:02 PM...12...22...15...Northrup landing 07:32 PM...12...22...45...205 EAFB TIG 08:36 PM...12...23...49...EAFB landing
The forecast for the Kennedy Space Center calls for scattered clouds at 2,000 and 5,000 feet and a broken deck at 10,000 feet. But there is a chance for a broken deck at 5,000 feet and a chance for showers within 30 nautical miles, both flight rule violations. Winds will be gusting to 22 knots, but the crosswind component for a landing on runway 15 is just 2 knots or so.
At Edwards, clouds are no problem but winds out of 290 degrees gusting up to 22 knots will result in a crosswind of about 20 knots for a landing on runway 22/04. The crosswind limit for a shuttle commander returning to Earth is 15 knots in daylight, 12 knots in darkness.
The outlook for Northrup Strip at White Sands calls for light winds and broken cloud decks at 15,000 and 20,000 feet. It is "go" for landing.
"OK, Roman, shoot, you could probably look out the window and see some of the weather we're talking about here," astronaut Ken Ham radioed shuttle commander Mark Polansky late today. "But the big picture regarding the Cape, there's a front that's kind of pushing through the panhandle that you've been reading about for the last couple of days, it's on its way over toward the Cape. What that means in the local area there is some areas of low clouds in the vicinity as well as some convergence and showers if you will, which are more or less very light and streaming in sporadically if you will from the southeast to the northwest across the runway, which results in winds pretty much right down the runway.
"The official forecast is few (clouds) at 2,000, scattered at 5,000, broken at 10,000 with the winds 150 (degrees) at 15 knots peaking at 22. However, we're carrying a chance of broken at 5 and rain showers within 30. So it's going to be just playing the game realtime at the Cape tomorrow and see how that pans out for us. Over."
"Copy all," Polansky replied. "Just another standard landing."
"You pretty much read right through that," Ham said. "Now where it gets interesting is looking out west. Edwards, there is a front more or less extending southwest to northeast, it's essentially in northern California right now, pushing southeast. ... That is predicted to be through the area of Edwards tomorrow, resulting in clear skies. The actual forecast is few (clouds) at 10,000 (feet), seven-mile vis. However, it's going to carry with it some real strong winds that are essentially perpendicular to the runway. Currently it's forecast at 290 (degrees) 15 peak 22, which is a peak crosswind of 20 knots. And along with that, some moderate turbulence in the middle altitudes.
"However, over at Northrup, that will still be ahead of that front tomorrow," Ham said. "The forecast there is broken at 15, broken at 20,000, good visibility, light winds. So Northrup right now is a go forecast. But as time progresses, that front may push into Northrup, making Northrup worse and making Edwards better as we move into Saturday. Do you have any questions there?"
"No, no questions at all on the weather."
"OK. So the big picture for tomorrow regarding strategy is, we're going to try for the Cape on the first rev. And second rev, we're looking predominantly at the Cape and Edwards. And then the third rev we'll be looking mostly at Edwards and Northrup. ... Having said that, you pretty much have an equal chance to land at any given site there. If it turns out tomorrow that Northrup is our only 'go' site, that's where we'll be sending you."
"OK. That's what we've been reading in the messages and what we've been expecting, so we will be prepared to go wherever and we've got our betting pools on board, we'll go ahead and talk about them after we land," Polansky said.
Assuming the weather provides any chance at all, Polansky, pilot William Oefelein and their crewmates will shoot for a landing in Florida on the first opportunity. That would require a three-minute 17-second rocket firing on orbit 202, lowering the shuttle's velocity by about 222 mph. After a half-hour free fall, the shuttle would enter the discernible atmosphere at an altitude of 400,000 feet - entry interface - at around 3:24 p.m. At that point, the orbiter would be 5,100 miles from runway 15 at the Kennedy Space Center with touchdown expected at 3:56:12 p.m.
Here are preliminary numbers for a KSC entry on orbit 202 (in EST; minor changes expected):
EST...........EVENT 10:49:00 AM...Begin deorbit timeline 11:04:00 AM...Radiator stow 11:14:00 AM...Mission specialists seat installation 11:20:00 AM...Computers set for deorbit prep 11:24:00 AM...Hydraulic system configuration 11:49:00 AM...Flash evaporator checkout 11:55:00 AM...Final payload deactivation 12:09:00 PM...Payload bay doors closed 12:19:00 PM...Mission control 'go' for OPS-3 entry software load 12:29:00 PM...OPS-3 transition 12:54:00 PM...Entry switchlist verification 01:04:00 PM...Deorbit parameters update 01:09:00 PM...Crew entry review 01:24:00 PM...Commander, pilot don entry suits 01:41:00 PM...Inertial measurement unit alignment 01:49:00 PM...CDR/PLT strap in; mission specialists suit don 02:06:00 PM...Shuttle steering check 02:09:00 PM...Hydraulic power system prestart 02:16:00 PM...Toilet deactivation 02:24:00 PM...Vent doors closed for entry 02:29:00 PM...Mission control 'go' for deorbit burn 02:35:00 PM...Mission specialists seat ingress 02:44:00 PM...Single APU start 02:49:05 PM...Deorbit ignition 02:52:22 PM...Deorbit burn complete 03:24:19 PM...Entry interface 03:29:19 PM...1st roll command to right 03:36:33 PM...1st left-to-right roll reversal 03:49:46 PM...Velocity less than mach 2.5 03:51:53 PM...Velocity less than mach 1 03:52:40 PM...253-degree left overhead turn to line up on runway 03:56:12 PM...Landing