The seventh time was the charm for NASA's two cloud-watching satellites: After six delays, a Boeing Delta 2 rocket finally launched the spacecraft into orbit before dawn Friday.
CloudSat and CALIPSO are designed to give unique views of how clouds form and how they affect weather and climate — in turn leading to better weather forecasts, NASA says. They will join three other satellites already surveying the Earth's atmosphere.
NASA has been trying to launch the satellites almost every night for a week, but a series of glitches and bad weather repeatedly held up the launch from Vandenberg.
Last Friday, the initial launch attempt was scrubbed just 48 seconds before liftoff, because of a temporary problem with communication links.
Saturday's launch attempt was called off because a refueling aircraft was unavailable to service a tracking plane due to monitor the launch. Hours before Sunday's scheduled attempt, NASA reported that the refueling plane was still unavailable — resulting in the third postponement.
The scheduling problems were resolved in time for another countdown early Tuesday, but high upper-level winds forced the fourth delay. Then, clouds over Vandenberg led NASA to call off Wednesday's countdown.
Thursday's launch attempt was called off due to a suspected problem with a temperature sensor on the rocket. Engineers and mission managers were worried that the sensor would have to be replaced, NASA said.
However, after analyzing the data, managers concluded the unusual sensor readings "were primarily the result of higher temperature pressurization rates and are not indicative of any defect in the sensor," the space agency said in an advisory later Thursday.
"The sensor does not require replacement and can fly as is," it said. That set the stage for Friday's launch.
The CloudSat and CALIPSO missions suffered repeated delays even before last week's first countdown. Originally, the satellites were to have launched last year, but technical problems and a strike by Boeing workers kept them grounded.
This report includes information from MSNBC.com and The Associated Press.