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Twin spacecraft enter lunar orbit over New Year's weekend

Monday - 1/2/2012, 12:53pm  ET

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NASA's twin GRAIL spacecraft will map the moon's gravity field. The two probes entered orbit around the moon over New Year's weekend. (Courtesy of Jet Propulsion Laboratory)

Greg Redfern, wtop.com

WASHINGTON - Happy New Year everyone! I hope that 2012 will find you safe, healthy and prosperous. We will have many adventures together as we explore the universe in 2012.

NASA was busy over New Year's Eve and New Year's Day as its twin lunar spacecraft, GRAIL-A and -B entered lunar orbit after a 3 month, 2.5 million mile journey.

GRAIL - Gravity Recovery and Interior Laboratory - is a $496 million mission designed to map the interior of the Moon in a most unique way, using radio signals.

As reported by NASA, "GRAIL-B achieved lunar orbit at 2:43 p.m. PST (5:43 p.m. EST) Jan. 1, while GRAIL-A successfully completed its burn Dec. 31 at 2 p.m. PST (5 p.m. EST). The insertion maneuvers placed the spacecraft into a near-polar, elliptical orbit with an orbital period of approximately 11.5 hours. Over the coming weeks, the GRAIL team will execute a series of burns with each spacecraft to reduce their orbital period to just under two hours. At the start of the science phase in March 2012, the two GRAILs will be in a near-polar, near-circular orbit with an altitude of about 34 miles (55 kilometers)."

The Moon is an average of about 250,000 miles away but the GRAILs took an economic route as they were launched by the same rocket, a Delta II.

More powerful and expensive rockets could have cut the transit time but during the cruise phase the time was used to check out and prepare onboard systems.

This latest lunar mission will give us the most detailed data of the Moon's interior by mapping the Moon's gravitational field.

The mapping will be accomplished by monitoring the slightest deviations in radio signals that will be constantly transmitting between the two spacecraft. Analyzing these variations in conjunction with the spacecrafts' location will lead to the determination of the composition and structure of the lunar interior.

When all of the data from previous and current lunar missions is added we will have a very good data set for our Moon. Right now we know more about Mars than we do our own Moon.

Read more about the mission to the moon, follow this .

The sky daily blog to keep up with the latest news in astronomy and space exploration.

You can email Redfern at skyguyinva@gmail.com.

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