NASA's Twin GRAIL Craft On Their Way To the Moon

sighted writes "The twin lunar Gravity Recovery and Interior Laboratory (GRAIL) spacecraft lifted off from Cape Canaveral this morning. GRAIL-A is scheduled to reach the moon on New Year's Eve 2011, while GRAIL-B will arrive New Year's Day 2012. The two solar-powered spacecraft will fly in tandem orbits around the moon to measure its gravity field. Lunar explorers hope the mission will answer longstanding questions about the moon 'from crust to core.'"

Comments

Why so long to the moon?

[ctmurray]

I am sure there is a good reason, I just cant find it. Seems like a long time to get to the moon.

Re:Why so long to the moon?

[srepetsk]

Unlike the Apollo program missions, which took three days to reach the Moon, GRAIL will make use of a three- to four-month low-energy trans-lunar cruise via the Sun-Earth Lagrange point L1 to reduce fuel requirements, protect instruments and reduce the velocity of the two spacecraft at lunar arrival to help achieve the extremely low 50 km (31 mi) orbits with separation between the spacecraft (arriving 24 hours apart) of 175 to 225 km (109 to 140 mi). http://en.wikipedia.org/wiki/Gravity_Recovery_and_Interior_Laboratory

These are analogous to successful GRACE pair

[Thagg]

The article unfortunately doesn't say this, but these satellites are very similar to the GRACE pair of satellites still orbiting the earth. There are a couple of things that make this different.

1) One of the limitations GRACE has is that the satellites have to orbit pretty high, to stay out of the influence of the Earth's atmosphere. Their orbits are about 300 miles high, and that limits the resolution of the gravity map to dozens of miles at very best. GRAIL will not have that limitation, and I hope they can fly the satellites much lower. The tidal forces of the Earth at the Moon are probably about 100 times stronger than our tides from the Moon, that might limit how low they can fly -- but it should allow a much more precise measurement of the Moon's gravity map than we have of Earth.

2) One of the fascinating things about GRACE, that has proven more exciting than would have thought possible, is that the Earth's gravity is a function of time. GRACE is able to detect when large areas of earth are saturated with water, or changes in ocean currents, from the change in gravity. The Moon probably doesn't change at all. If they do detect changes, though...that would be exciting!

Re:These are analogous to successful GRACE pair

[Hartree]

"I wonder what will happen if they find a strong magnetic anomaly near Tycho crater?"

Then Metro Goldwyn Mayer and the MPAA will file a copyright infrngement suit against the universe.

Re:what time Zone is the moon in?

[Nyeerrmm]

Technically, everything is done UTC, and the insertion burn for GRAIL-A is around 22:00 UTC on 31-Dec-2011, and GRAIL-B is after that.

Of course, the people operating it are stationed in Pacific and Mountain time zones (JPL/DSN and Lockheed Martin in Denver), and that places the maneuvers mid-afternoon on those days.

GRAIL mission name called into question

[Anonymous Coward]

The mission is for "measuring" gravitation, not "recovering" it. Has it occurred to anyone else that a more straightforward name would be the lunar "Gravity Measurement And Interior Laboratory?" Or does the corresponding acronym bother someone?

Historic

[Nerdfest]

I'm very much looking forward to this mission. Isn't this how we discover the monolith?

Re:Is There A Reason...

[fnj]

Because it costs 4 bucks a gallon now, you know.

Re:a couple of thoughts

[Mindcontrolled]

In what manner would you even restart a magnetosphere? I think we are a couple of orders of magnitude out of the realm of our current possibilities here.

Re:youtube of launch

[gr8dude]

Hmm.. if you pay attention to the voice, you notice they still use "miles per hour" and "miles" - I thought they switched to the metric system.