September 10, 2011
Successful Liftoff For NASA’s GRAIL Spacecraft
Initially, GRAIL had been scheduled to liftoff from Cape Canaveral's Launch Complex 17B on Thursday at 8:37 a.m. However, high winds forced a delay until Friday morning at 9:16 a.m. That scheduled launch would also be pushed back, however, as once-again upper-level winds reportedly posed a threat to the spacecraft.
The Saturday launch had initially been set for 8:29 a.m. Saturday. However, the countdown clock had reached a second scheduled hold, at the T-4 mark, before NASA received reports that winds in the 15,000 to 22,000 foot atmospheric region were "unacceptably high," as reported on the GRAIL launch blog. The team then turned their attention to a second opportunity for liftoff at 9:08 a.m. EDT.
At 8:55 a.m., NASA reported that the winds had died down enough for the liftoff to occur. Three minutes later, Launch Director Tim Dunn confirmed that his team would be ready to launch. By 9:06 a.m. the United Launch Alliance (ULA) Delta II heavy rocket carrying the crafts into space had been armed for ignition and liftoff.
Less than a minute later, NASA declared that all systems were "go" for launch. At eight seconds until 9:09 a.m. EDT, the twin GRAIL spacecraft were officially en route to the moon.
"Because of the precision required to send the GRAIL spacecraft on the right course to the moon, the launch windows for GRAIL are instantaneous, only a single second long," NASA officials explained on the GRAIL mission launch blog. "So any delay pushes the countdown outside the window, which is what happened Thursday and this morning with late word that high level winds were outside limits."
The primary objective of the GRAIL project is to "determine the structure of the lunar interior, from crust to core, and to advance understanding of the thermal evolution of the moon," according to a Saturday morning post to the launch news section of the mission's official homepage.
As previously reported here on RedOrbit, GRAIL consists of two near-twin spacecraft, both of which are approximately the size of a washing machine, according to NASA. The slight difference in size is necessary so that one vehicle will follow the other while they circle the moon, the space agency said.
Once they achieve lunar orbit (a process that requires 3-4 months for them to arrive and up to an additional 8 weeks for the vehicles to reshape and merge their orbits), the spacecraft will transmit radio signals through their payload, the Lunar Gravity Ranging System. This will precisely measure the distance between them down, though regional gravitational differences on the moon are expected to expand and contract that distance.
"The improvement that Grail will have for the gravity field on the nearside is a factor of 100 better than we have right now, and on the farside it is a factor of 1,000," GRAIL scientist Dr. Robert Fogel told BBC News science correspondent Jonathan Amos on Saturday. "Imagine trying to see something microscopic with your own eyes and then putting a lens in front of them that has 100 times power or 1,000 times power--it becomes a different world; and that's what we'll get with Grail."
The two crafts, identified by the aeronautics administration as GRAIL-A and GRAIL-B, will also include a set of cameras that will be used for educational and public outreach purposes--the first time in NASA history something like this has been attempted.
"Trying to understand how the moon formed, and how it evolved over its history, is one of the things we're trying to address with the GRAIL mission," Maria Zuber, principal investigator for GRAIL from the Massachusetts Institute of Technology (MIT), said in a Sept. 2 statement.
"But also, (we're) trying to understand how the moon is an example of how terrestrial planets in general have formed," she added, calling GRAIL "a mission that will study the inside of the moon from crust to core."
According to Associated Press (AP) reports, the mission's price tag will be $496 million.
Image 2: Using a precision formation-flying technique, the twin GRAIL spacecraft will map the moon's gravity field, as depicted in this artist's rendering. Radio signals traveling between the two spacecraft provide scientists the exact measurements required as well as flow of information not interrupted when the spacecraft are at the lunar farside, not seen from Earth. The result should be the most accurate gravity map of the moon ever made. The mission also will answer longstanding questions about Earth's moon, including the size of a possible inner core, and it should provide scientists with a better understanding of how Earth and other rocky planets in the solar system formed. GRAIL is a part of NASA's Discovery Program. Image credit: NASA/JPL-Caltech
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