Thursday, December 29, 2011

GRAIL A & B Set for Lunar Orbit

Hey Space Placers!

Once again spacecraft are preparing to orbit my favorite place in the Universe - our Moon. NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission with its two spacecraft, is set for a major mission milestone - entering lunar orbit - this New Year's weekend.

GRAIL A & B will enter lunar orbit on New Year's Eve and New Year's Day respectively, at 1:21 p.m. PST (4:21 p.m. EST) for GRAIL-A and 2:05 p.m. PST (5:05 p.m. EST) for GRAIL-B. 

From NASA's Press Release yesterday: 
As of Dec. 28, GRAIL-A is 65,860 miles (106,000 kilometers) from the Moon and closing at a speed of 745 miles per hour (1,200 kilometers per hour). GRAIL-B is 79,540 miles (128,000 kilometers) from the Moon and closing at a speed of 763 mph (1,228 kilometers per hour).

During their final approaches to the Moon, both orbiters move toward it from the south, flying nearly directly over the lunar south pole. The lunar orbit insertion burn for GRAIL-A will take approximately 40
minutes and change the spacecraft’s velocity by about 427 mph (688 kilometers per hour). GRAIL-B’s insertion burn 25 hours later will last about 39 minutes and is expected to change the probe’s velocity
by 430 mph (691 kilometers per hour).

The insertion maneuvers will place each orbiter into a near-polar, elliptical orbit with a period of 11.5 hours. Over the following weeks, the GRAIL team will execute a series of burns with each spacecraft to reduce their orbital period from 11.5 hours down 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).

When science collection begins, the spacecraft will transmit radio signals precisely defining the distance between them as they orbit the Moon. As they fly over areas of greater and lesser gravity, caused
both by visible features such as mountains and craters and by masses hidden beneath the lunar surface. they will move slightly toward and away from each other. An instrument aboard each spacecraft will
measure the changes in their relative velocity very precisely, and scientists will translate this information into a high-resolution map of the Moon’s gravitational field. The data will allow mission scientists to understand what goes on below the surface. This information will increase our knowledge of how Earth and its rocky neighbors in the inner solar system developed into the diverse worlds we see today.

GRAIL will give us information about the Moon's interior that will be able to answer many questions about the origin and evolution of the Moon. We will be able to combine GRAIL's results with those of Lunar Reconnaissance Orbiter (LRO) and thereby develop our most detailed understanding of the Moon. 

I can hardly wait.
GRAIL Artist's Rendition

Sky Guy in VA

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