Shuttle Discovery's obsolete code could force launch delay
- By Aliya Sternstein
- Nov 13, 2006
The computers aboard Space Shuttle Discovery won’t know what time it is when Jan. 1, 2007, arrives, a problem that could force NASA to delay the launch.
The shuttle is set to launch Dec. 7 for a 12-day mission to do construction work on the International Space Station, but now agency officials are devising workaround plans in case bad weather or other issues force a postponement. If NASA can’t launch the shuttle by Dec. 18, officials might wait until after the new year to avoid any possible time code synchronization problems with ground control computers. It is also possible that astronauts might try to reinitialize the onboard software on Jan. 1, while the shuttle is in flight.
The shuttle software code was designed 30 years ago to run periodically, not for lengthy periods, so the computer code does not recognize the end of a calendar year, NASA spokesman Kyle Herring said. On Jan. 1, the computers will think it is day 366 of 2006. The software would then believe the master timing is wrong and revert to the shuttle computer’s internal clock.
Herring said that if the launch cannot be timed to avoid having the shuttle in flight when the year changes, the astronauts will have to spend about four to six hours reprogramming the computers.
“There’s a procedure to do all that, but it’s time-consuming,” he said. “It is not a safety of flight issue.” NASA has performed a successful simulation of the procedure in its Shuttle Avionics Integration Laboratory, Herring added.
Before this year, NASA had no reason to upgrade the computers’ software because the agency always had enough flexibility in its flight schedule to avoid launching the shuttle during the last few weeks of the year, Herring said.
But the agency has a limited amount of time to assemble the International Space Station before retiring the shuttle fleet in 2010. NASA is trying to accomplish three shuttle missions this year, he said.
If the shuttle must be in flight during the year-end rollover, adjusting the clock will not be optional. The shuttle’s computer must be synched with the ground computers in mission control.
Unsynchronized computer clocks could limit mission control’s ability to communicate with the astronauts, said former astronaut Steve Oswald, who is a vice president and program manager at Boeing, a shuttle subcontractor whose flight software division deals with software issues.
If the crew were not able to reconfigure the software, Herring said, “we’re not sure exactly to what degree that would affect voice and command capability. There’s a high level of confidence that you wouldn’t lose voice and command, but we don’t know that.”
In addition, there is a chance the shuttle might lose some Global Positioning System data during re-entry if its software clock were to go out of synch with the ground, he said.
Boeing spokesman Ed Memi said NASA chose not to upgrade the software when it ramped up the space program in 2004 because of budget constraints. Changing the software would require recertifying it to meet various standards, which is a costly process, he said.