BY JUSTIN RAY
December 18, 1999 -- Follow the countdown and launch of a Lockheed Martin Atlas 2AS rocket and NASA's Terra spacecraft. Reload this page for the very latest on the mission.
FRIDAY, DECEMBER 17, 1999
We will provide further updates as news becomes available.
0330 GMT (10:30 p.m. EST)
The software problem caused the ground launch sequencer, the master computer program running the countdown, to incorrectly determine the Atlas rocket had not switched to internal power. The countdown was halted at T-minus 39 seconds. To correct the problem the software logic will be changed.
However, to ensure a similar problem does not exist in the software for the remainder of the countdown, officials decided late Thursday check the rest of the program.
THURSDAY, DECEMBER 16, 1999
During an automatic software check of rocket systems at T-minus 40 seconds, the sequencer did not confirm that the Atlas stage had switched to internal power. That resulted in a computer-commanded cutoff of the countdown at T-minus 39 seconds. The launch team used other methods to show the rocket was, in fact, on internal power and that the problem was with the ground software and not Atlas. But given the short launch window officials were not able to determine why the software acted the way it did and recycle the countdown.
Work is now under way to correct the ground launch sequencer software logic and test it in Lockheed Martin's software verification laboratory. This work should be completed in time to support another launch attempt on Friday during a window of 1833:25 to 1857:49 GMT (1:33:25-1:57:49 p.m. EST).
U.S. Air Force weather forecasters say there is a 90 percent chance of acceptable conditions on Friday.
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At Space Launch Complex-3 East, the liquid oxygen and liquid hydrogen will now be drained from the Atlas rocket and Centaur upper stage. Later the mobile service tower will be returned to around the rocket.
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The Atlas booster stage is now going to internal power.
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Also, the intruder aircraft was a glider, officials say.
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The mission to place Terra into the proper low-Earth orbit will take less than 14 minutes. At separation, the apogee altitude should be 376 nautical miles, perigee of 354 nmi and inclination of 98.3 degrees
1814 GMT (1:14 p.m. EST)
1813:25 GMT (1:13:25 p.m. EST)
The Atlas booster and Centaur upper stage are now fully fueled for launch, work that has been on going over the past 90 minutes. But given the super-cold temperatures of the liquid oxygen and hydrogen aboard the vehicle, the cryogenics will be replenished as the countdown continues. The Atlas was loaded earlier with its RP-1 fuel, a highly refined kerosene.
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Today's launch will occur from Space Launch Complex-3 East at Vandenberg Air Force Base in California. Since its last launch in May 1995, the pad has undergone complete reconstruction to support the larger, more complex Atlas 2-series of rockets and their Centaur upper stages. The renovation contract was signed in late 1992 to build the new pad so Atlas 2 rockets could launch secret spy satellites for the National Reconnaissance Office from the U.S. West Coast, placing the craft into orbits that cannot be reached with launches from Cape Canaveral in Florida.
The old tower was demolished and rebuilt from the ground up. Construction was completed in September 1996 and the first Atlas rocket, the one flying today, was stacked on the pad in September 1997.
SLC-3E consists of the 230-foot tall mobile service tower that enclosed the rocket when it is at the pad, providing access and weather protection; the 170-foot tall fixed umbilical tower that supports lines connected to the rocket through which propellants are pumped to the rocket, as well as electrical power and conditioned air; the launch support building is a two-story structure contains support equipment; and the launch operations building where the countdown is controlled, located about 7 miles from the pad.
To date, there are three scheduled launches from the new pad: Terra today and two NRO payloads next summer and one about a year later.
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The latest weather forecast has been improved to a 100-percent chance of acceptable conditions today. The launch time forecast calls for just some scattered cirrus clouds at 24,000 feet, a temperature of 59 degrees F and northeasterly winds at 8 to 12 knots.
1603 GMT (11:03 a.m. EST)
It is a clear, beautiful morning in California. There are no problems being reported and launch remains scheduled to occur on time in 2 1/2 hours at 1833:25 GMT (1:33:25 p.m. EST).
1535 GMT (10:35 a.m. EST)
The Atlas rocket to be launched today was assembled at SLC-3E in September 1997 to support pathfinder exercises at the newly rebuilt pad. Those tests to check the pad, ground support equipment and launch team were completed in April of 1998. However, the Terra satellite was grounded due to software problems, forcing the Atlas rocket to be placed in extended storage.
Lockheed Martin officials decided the best place to keep the Atlas was on the launch pad enclosed in the mobile service tower. The MST at Vandenberg is unlike the more open towers at Cape Canaveral Air Station's Complex 36 Atlas pads. The Vandenberg tower is often referred to as a building, fully enclosed and environmentally controlled. In addition, workers closed off the base of the tower and erected a tent around the base of the Atlas to protect the engines. Dry, warm air was also pumped into the tent.
Throughout the past two years the rocket has been coated with WD-40 to prevent corrosion. WD-40 was originally created 40 years ago for the Atlas ICBMs. X-ray tests were also performed every 90 days to check the structural integrity of the rocket's fuel tanks.
In May of this year when the decision was made to resume the launch campaign for Terra, Lockheed Martin reperformed tests and checkout of the pad and rocket for for today's mission, said Mark Ware, manager of launch operations at SLC-3. Launch pad validations were completed as if the rocket was never there. "It was like starting fresh."
When the work resumed the launch was planned for late July. However, when the Boeing Delta 3 rocket failed on May 4, another delay for Terra was triggered. The upper stage engine that caused the Delta 3 mishap is a similar version to the engines on the Atlas rocket's upper stage - Centaur. To ensure the engines on Centaur were safe to use, a pair of ultrasonic inspections were performed at the launch pad to check the engines' combustion chambers to see if the problem that doomed Delta 3 would affect Terra's ride. The inspections and later analysis concluded that the Centaur was ready for flight. The launch was rescheduled for today.
1330 GMT (8:30 a.m. EST)
The latest weather forecast calls for clear skies, unrestricted visibility, a temperature of 55 degrees and a 90 percent chance of meeting the launch weather rules.
0130 GMT (8:30 p.m. EST)
The only problem being worked Wednesday was with a remote interface controller, a piece of ground hardware that allows the launch processing system in the control center to communicate with launch pad systems to service the rocket and monitoring Atlas systems. During a test Tuesday, a system shut down and a backup did not take over as it should have. However, engineers troubleshooting the problem determined late Wednesday that an error in procedures caused the glitch. The RIC was properly initialized and rebooted Wednesday, clearing the problem at SLC-3E.
So with no other problems and a near-perfect weather forecast officials are pressing ahead with liftoff at 1833:25 GMT (1:33:25 p.m. EST), the opening of a 24-minute, 24-second launch window that will extend to 1857:49 GMT (1:57:49 p.m. EST).
"We are basically in a ready state with the launch vehicle, space vehicle, the facilities and launch team," said Ray Lugo, NASA's mission director for the Terra launch.
Final pre-launch activities will get under way with a weather briefing at 1000 GMT (5 a.m. EST) for management before entering countdown operations. The Atlas will be powered up at 1018 GMT (5:18 a.m. EST). A communications test between NASA's Tracking and Data Relay Satellite System and Terra will be performed at 1200 GMT (7 a.m. EST). About 90 minutes later the launch team will switch the purge into the payload fairing from air to gaseous nitrogen. Another weather briefing will be held at just after 1500 GMT (10 a.m. EST) so managers can decide whether to roll the protective mobile service tower away from the rocket. Tower retraction is planned to begin at 1533 GMT (10:33 a.m. EST). Following a built-in hold in the countdown, fueling of the Centaur upper stage with liquid oxygen and liquid hydrogen and Atlas with liquid oxygen will occur in steps. A final hold will take place at T-minus 5 minutes.
We will have complete comprehensive updates throughout the final hours of the countdown and the 14-minute flight by Atlas to place Terra into orbit.
WEDNESDAY, DECEMBER 15, 1999
TUESDAY, DECEMBER 14, 1999
Workers today performed final closeouts of the electrical and mechanical systems on the Atlas booster and Centaur stage thrust sections. Final pre-launch work to prepare the spacecraft is also beginning. The launch readiness review is planned for Wednesday morning.
U.S. Air Force weather forecasters say there is a 90 percent chance of acceptable conditions for launch on Thursday. The only slight concern will be layered clouds. The launch time forecast calls for scattered altostratus clouds at 18,000 feet and scattered cirrus clouds at 24,000 feet, visibility of 7 miles, northerly winds 8 to 12 knots and a temperature between 52 and 56 degrees F.
Launch weather officer Capt. Joe Kurtz provided this summary in today's forecast:
"An upper level ridge and surface high pressure continue to build into the west coast. The Vandenberg area will have partly cloudy skies over the next few days. Scattered mid and high clouds will move over the ridge into California on launch day. Winds will be gusty around base Tuesday morning, but they should decrease as we go through the week. On launch day, surface winds will be out of the east early in the count, becoming northeasterly for liftoff. Overnight low temperatures this week will range in the upper 30's to around 40 F, with the highs in the upper 50's to lower 60's. Maximum upper level winds will be 30 knots from the northwest at 30,000 feet."
Terra is a $1.5 billion mission that will serve as NASA's flagship for the Earth observing system, a multi-satellite program designed to study the global environment over the next decade.
Flight data file
Vehicle: Atlas 2AS
Launch date: Dec. 18, 1999
Launch window: 1833-1858 GMT (1333-1358 EST)
Launch site: SLC-3E, Vandenberg Air Force Base, Calif.
The countdown for the launch of NASA's Terra spacecraft aboard an Atlas 2AS rocket is cutoff in the final minute.
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Atlas vehicle data - Overview of the rocket that will launch Terra into space.
Terra spacecraft - Facts and information about NASA's Terra satellite.
Launch timeline - Chart with times and descriptions of events to occur during the launch.
Pre-launch photo gallery - Follow the rocket and satellite preparations for launch in pictures.
Terra's mission - A NASA release detailing the objectives and science goals of Terra.
Atlas index - Listing of our previous Atlas coverage.
Explore the Net
International Launch Services - Lockheed Martin-led consortium which globally markets the U.S. Atlas and Russian Proton rockets.
Lockheed Martin Astronautics - U.S. company which builds and launches the Atlas family of rockets.
Terra - NASA's flagship mission for the Earth observing system.
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