http://www.orlandosentinel.com/news/custom/space/orl-asecssmsensor13021303feb13,%5C0,1610938.story?coll=orl%2Dnews%2Dheadlines
exerpt follows:
A sensor indicated shuttle Columbia's left landing gear was down and locked 26 seconds before radio contact with the orbiter was lost, according to internal NASA documents obtained by the Orlando Sentinel.
If the sensor reading was accurate, it signaled disaster for Columbia, which broke apart above central Texas on Feb. 1, killing seven astronauts. However, at the same time, two other sensors were indicating the landing gear was safely retracted in Columbia's wheel well.
Engineers aren't certain if the reading showing a deployed landing gear was real or the result of a faulty sensor that sent bad data as the ship's systems began to fail.
The document obtained by the Sentinel is the first time the data from the landing-gear sensor have been made public. Though NASA in the past week has released information about 17 other sensors that showed abnormal readings during the shuttle's final moments, officials have said nothing about the possibility that the landing gear may have suddenly deployed.
"There is nothing sinister about this at all," NASA spokesman Kyle Herring said. "They think this was a sensor reading and not an actual event."
The landing-gear sensor is yet another puzzle for investigators to solve as they try to determine what brought down the shuttle. Engineers are focusing on what happened to Columbia's left wing and the left-side wheel well, both of which apparently were struck by a doormat-sized chunk of insulating foam that peeled off the shuttle's external fuel tank during liftoff.
As the shuttle continued its fiery descent over California shortly before 9 a.m. on Feb. 1, sensors began shutting down or displaying temperature increases of up to 40 degrees in the left wheel well.
The new timeline, as well as other information obtained by the Sentinel, indicate that the Mishap Response Team investigating the disaster may be making some progress in understanding what happened.
For example, a new study looking at the temperature rise in Columbia's left wheel well has concluded that only an opening in the wheel well or wing cavity could account for the rising heat shown by the sensors, said a Johnson Space Center manager who asked to remain anonymous.
One of the first indications that something was wrong aboard Columbia came at 8:52 a.m., when brake line temperatures in the left landing gear started to rise. Nine sensors in and around the left wheel well showed temperatures continued to increase.
The JSC manager said the new analysis shows that loss of the shuttle's heat-resistant thermal tiles would not be enough to account for the temperature spike. Instead, the super-hot plasma that surrounds the shuttle during entry would have to have found a way inside.
"The bottom line," the manager said, "is we had to have had plasma flow into the wheel well or wing cavity." That finding, if confirmed, could be consistent with some sort of breach in the left wheel door.
Managers learn of reading
Information about the landing-gear sensor is one of several new details contained in a confidential Feb. 11 timeline of the accident drafted by the Mishap Response Team at Johnson Space Center.
The landing-gear deployment signal had earlier appeared on an internal timeline circulated among NASA managers on Feb. 4 -- three days after the shuttle disintegrated. That timeline is similar to summaries released publicly last week showing sensors on the shuttle's left side either shutting down or registering higher temperatures. But the previously released summary stops just before a sensor began indicating that the left landing gear had dropped down.
The landing-gear sensor message came at 8:59:06 a.m. Saturday, about 10 seconds after sensors reading the ship's left landing gear tire pressures failed.
At this point in the shuttle's descent, the orbiter was still more than 200,000 feet high and moving at 12,500 mph. The landing gear is supposed to deploy at speeds below 345 mph and an altitude of 250 feet, according to NASA. Twenty-four seconds after the landing-gear signal came on, jets began firing to control Columbia's leftward drift, caused by as-yet unexplained aerodynamic drag on the orbiter's left wing. Within the next two seconds, sensors detected the maximum movement of the shuttle's wing flaps before all signals from the doomed craft suddenly ended.
The Feb. 11 timeline noted that at the time the signal was lost, the flaps' "rate of change still [was] increasing rapidly" in an effort to keep the Columbia on course.
In a briefing of reporters last Friday, shuttle project manager Ron Dittemore said NASA engineers could see that the shuttle's control system was fighting a "losing battle" against the drag on the left wing.
"Even though we were still flying straight and in a general attitude that we desired, we can see that the aero-surfaces were continuing to increase in their magnitude to counter the drag," he explained.
"The jets were firing, again to counter the drag. And when we lost data, they were still holding control of the vehicle."