CAPECANAVERAL, Fla. - NASA engineers are meeting today determine whether to goforward with the planned Sunday launch of the space shuttle Atlantis despite asuspect fuel tank sensor system.
Top missionmanagers are meeting to decide whether to proceed with a Sunday afternoonlaunch for Atlantis with some stricterflight rules in place, or take more time to study an intermittent glitchwith fuelgauge sensors at the bottom of the orbiter?s 15-story external tank.
?Theproposal?s on the table,? NASA shuttle program manager Wayne Hale said lateFriday. ?We?re very cognizant of the fact that you don?t like to accept risk atthe launch site.?
Commandedby veteran shuttle flyer Stephen Frick, Atlantis? STS-122crew is charged with delivering the European Space Agency?s Columbus laboratory to the International Space Station (ISS). A Sunday launch attempt, ifapproved, would lift off at about 3:21 p.m. EST (2021 GMT), with currentforecasts predicting an 80 percent chance of good weather.
Mission managers called off a Thursdaylaunch attempt after two of four engine cut-off sensors in the liquidhydrogen portion of the shuttle?s fuel tank failed a standard check. A thirdsensor also acted later as the fuel tank was drained. NASA flight rules callfor three of the four sensors to be working properly in order to launch.
?We prettymuch came to the conclusion that we are in an area that we have got a suspectsystem,? said Hale, adding that the sensors are based on 1960s, Apollo-eratechnology.
The sensorsserve as a backup system to shut down Atlantis? three main engines before its propellantsupply runs dry. Space shuttles consume more than 500,000 gallons (1.9 millionliters) super-chilled liquid hydrogen and liquid oxygen propellant duringlaunch.
NASA has wrangledwith the fuel sensor glitches since the agency resumed shuttle flight in 2005following the Columbia tragedy. After modifying the sensors and adding extramonitoring devices to ensure they work properly, NASA is still at a loss toexplain their intermittent behavior.
?We?d like tohave certainty,? Hale said. ?We would like to know root cause.?
For Sunday?slaunch attempt, NASA is looking at tightening the sensor rule to require allfour units to be working properly before attempting a liftoff. As an extrameasure, they may also shorten the daily five-minute launch window to onesingle minute to conserve fuel in case the suspect sensors fail during flight.
?We don?twant to get launch fever,? Hale said. ?Even though the Columbus is out thereloaded in the payload bay and everybody is anxious for us to launch that guy,we want to make sure that when we go launch, it is safe or as safe as it everis in this normally risky business.?
NASAwill broadcast Atlantis' STS-122 mission live on NASA TV. Click here for SPACE.com's shuttle mission coverage and NASATV feed.
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