NASA has launched its third lunar probe in five years - an unmanned spacecraft that will study the moon's atmosphere.
Blazing a red path in the night sky, the spacecraft lifted off from NASA's Wallops Flight Facility in Virginia yesterday aboard a converted Air Force ballistic missile.
"The spacecraft is in good health and a good orbit at this point," said NASA commentator George Diller about half an hour after the launch.
Its mission is to learn more about the atmosphere and dust while circling the moon.
When US astronauts walked on the moon more than 40 years ago, they learned that dust could be a huge problem for sensitive spacecraft and equipment, said space expert John Logsdon.
"If we were ever to go there with people for long duration, the dust gets in everything," said Logsdon, a NASA adviser and former director of the Space Policy Institute at George Washington University.
"All the Apollo crews complained about the lunar dust getting everywhere."
US astronauts walked on the moon in 1969, and the last explorers of the Apollo era visited in 1972.
The journey to the moon will take about a month and the probe will initially orbit at a height of about 250km for 40 days before moving lower.
After 100 days of measuring chemical variations in the lunar atmosphere, analysing gases and lunar dust grains and looking for water molecules in the lunar atmosphere, the spacecraft will plunge into the moon's surface.