It’s now just two weeks until the start of the NASA Tweetup for the GRAIL moon mission. I’d like to bring you up to date about the developments that have occurred during the last week.
Group Organization -- Patches, Posters and Snacks: It’s been interesting to watch the group of nearly 150 attendees organize themselves. That’s a pretty big group, and exactly at the Dunbar Number. Prior NASA Tweetup groups have organized informal outings away from the formal scheduled events, and this group has as well. There will be a dinner Tuesday night for those arriving in the afternoon or early evening (sadly, I’ll miss this since I’ll be driving up from Naples after work). There’s also a barbeque planned for Thursday afternoon after the launch--which I suspect they mean “grill” not actual slow-smoked barbeque, but I’ll let it slide. I should be able to attend that event, at least for a while, before driving home Thursday night. The group has also come up with a patch that’s being made for everyone who wants one (or several). Despite some initial analysis/paralysis around patch design, the group voted one as their favorite (several possible designs were submitted, discussed, and tweaked). And finally the group is currently voting on a poster that we can all sign and leave behind at the conclusion of the Tweetup. And all this was done on Facebook with very minimal organization (I almost said “adult supervision”). I think that’s pretty impressive for a group that size. This is obviously a group of smart and enthusiastic people.
Guests: We’ve learned a bit about some of the guests we can expect to meet at the Tweetup. In a press release shared with the media yesterday NASA announced that one of the participants would be Dr. Sally Ride, America’s first woman in space. Also, Nichelle Nichols, the original Star Trek’s Uhura, announced on Twitter that she would be attending the launch (so at least that part of the rumor turned out to be true).
The Long Way Around: I was initially puzzled after reading through the GRAIL mission material available on the web. It’s going to take 3-4 months for the twin satellites to arrive at the moon, and I wondered why it was going to take so long (after all, if you could drive to the moon in a car at 70 miles an hour, that’s about how long it would take to get there). The manned moon landings in the late 60’s and early 70’s only took a couple of days to get there, so the 3-4 month schedule sounded…odd. And this week I found out the answer: I assumed it had something to do with fuel savings (it does) but I wasn’t prepared for the circuitous route the GRAIL satellites are going to take. They are both going via the L1 Lagrange point between the Sun and the Earth (Caution: Science ahead!). What’s a Lagrange Point, you ask? Well, there’s a special case in what’s known as the multi-body problem in celestial mechanics (short version: if there are more than two objects you can’t in general predict how all the objects will interact with one another) discovered by Joseph-Louis Lagrange, an 18th century mathematician and astronomer. He discovered that when you had three celestial bodies (two relatively big, one tiny) there were five stable configuration points for the three: one with the tiny one between the other two, one with the tiny one on end or the other of a line connecting the two ones, and one 60° out on either side of the two big ones. Called Lagrange Points, these five places are points where a tiny satellite can “park” and stay with very little effort between the Sun and Earth (or Earth and Moon) because the gravity of the two big objects are at equilibrium. So in an effort to save fuel, the GRAIL satellites are going to the moon via the L1 point between the Earth and the Sun, which is approximately 3-4 times further away than the moon is. This requires a minimum amount of fuel to get to the L1 point, allows the two satellites to arrive at the moon in different orbits, and requires a minimum to insert them into the proper orbits when they arrive at the moon. So that mystery is solved.
So far, we haven’t gotten official word of what activities NASA has planned for the group (other than the general “tours in the morning” and “activities in the afternoon” for Wednesday). I’ll let you know what they tell us in a future update.
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