The exact launch time for the country's second lunar probe was announced as authorities said the mission faces three major challenges.

Chang'e-2, a circumlunar satellite that will test key technology involved in a soft-landing on the moon around 2013, is scheduled to blast off from the Xichang Satellite Launch Center at 6:59:57 PM on Friday, Wu Weiren, a spokesman for the China National Space Administration said.

If the launch misses that slot it could be rescheduled for Saturday or Sunday, he said.

Scientists denied that the launch time was chosen to mark National Day, saying the launch date was purely coincidental and determined by other factors.

The first challenge is whether the rocket can directly send the probe into the Earth-moon transfer orbit. Simply put, Chang'e-2 will go directly into Earth-moon transfer orbit rather than orbit the Earth first. The Chang'e-1 used a different procedure, orbiting the Earth first on its mission, Wu said.

The second challenge is whether the probe can be captured by the moon's gravitational pull. "If the braking is not well handled, the probe could either crash into the moon, or fly away (from the preset orbit)," he said. More >>>

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