GRAIL to try to launch again tomorrow

By Phil Plait | September 8, 2011 6:00 pm

[UPDATE: The launch of GRAIL has been postponed once again to Saturday, tomorrow. There are two launch windows; one at 12:29:45 UT and the other at 13:08:52 (08:29 and 09:08 Eastern US time). The weather forecast is iffy, so there may be another postponement. Stay tuned.]

NASA’s GRAIL mission — Gravity Recovery and Interior Laboratory, that is — was supposed to launch on September 8, but winds prevented takeoff. They will try again Friday (tomorrow) at 12:33:25 UTC (08:33:25 Eastern). Failing that, another launch window will be at 13:12:31 UTC (and lasts for only one second!). There are many more opportunities to launch until October 19, so I suspect NASA will play it safe. Emily Lakdawalla, as usual, has details.

GRAIL will head to the Moon, and is actually two separate spacecraft, each about a meter on a side. They will fly in formation, and use a suite of very sensitive detectors to essentially determine their distance from each other. The Moon is lumpy in its interior; in other words its density varies on the inside. This means an orbiting object will feel a slightly different pull of gravity with time as it circles the Moon. That change in gravity will change the orbital speed and therefore the distance between the two probes. They will be able to measure their separation to an accuracy of just a few microns… for comparison, a human hair is roughly 50 microns thick!

This will allow scientists to measure the interior distribution of mass inside the Moon, essentially probing its interior. The spacecraft also have cameras to take pictures of the Moon’s surface that will be available for schoolchildren, a project I think is very cool. But it’ll be a while: it will take a few months for the spacecraft to make their way into lunar orbit. They’re taking the scenic route, which saves fuel and allows a thorough checkout of the spacecraft.

You can watch the launch live on NASA TV.


Comments (19)

  1. Robin

    Al Einstein would dig this.

  2. Keith Bowden

    Sir Bedevere: …and that, my liege, is how we know the Earth to be banana shaped.
    King Arthur: This new learning amazes me, Sir Bedevere. Explain again how sheep’s bladders may be employed to prevent earthquakes.

  3. Michael

    Time to take our Gravity back!!!

  4. VinceRN

    Very cool, but it would be cooler if we were walking around up there.

  5. DLC

    And so, if she has the same gravitic attraction as a Duck, she must be . . . ?

  6. Robin

    @DLC (#5):

    ……she must be having a mass distribution such that local gravity is the same as a duck!

  7. @2. Keith Bowden : “Sir Bedevere: …and that, my liege, is how we know the Earth to be banana shaped.”

    Actually, Earth’s more potato-shaped as this :

    gravity map shows. 😉

    Although NOT as potato-shaped as Phobos and Diemos!
    (Click on my name for comparison images youtube clip.)

    @5. DLC : “And so, if she has the same gravitic attraction as a Duck, she must be . . . ?”

    A witch! 😉

    Reminder to y’all that there’s another NASA satellite due for launch next month too – details here :

    this time an Earth-observation climatology one. :-)

    This delay for GRAIL won’t affect the Oct. 25th launch date for the National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) will it? Anyone know?

  8. Seems there’s often a launch delay – hopefully that candle will be lit next time around. Best wishes to the GRAIL team for their next launch attempt. :-)

    One question : What’s the story with the turquoise middle section of the GRAIL rocket there? Anyone know why it’s that colour, please?

  9. DennyMo

    I understand the concept of the “launch window”, but am having a hard time figuring out how you have a launch window that’s only one second long! How is that possible?

  10. @ ^ DennyMo : Really accurate timing & very well synchronised stopwatches?* 😉

    Latest news from the GRAIL website – seems it’s been postponed again :

    Launch Now Targeted for Saturday, Sept. 10
    Fri, 09 Sep 2011 12:59:57 PM UTC+0930

    The launch of a Delta II rocket carrying NASA’s Gravity Recovery and Interior Laboratory (GRAIL) has been postponed one day to allow additional time to review propulsion system data from Thursday’s detanking operation after the launch attempt was scrubbed due to upper level winds. The launch now is planned for Saturday, Sept. 10 from Space Launch Complex-17B at Cape Canaveral Air Force Station, Fla. There are two instantaneous launch opportunities at 8:29:45 a.m. and 9:08:52 a.m.

    The countdown clock from there (click my name to visit source page.) is at
    1 day 31 minutes and 55 seconds at time of posting this.

    So looks like it won’t be today but, again, tomorrow. Third day lucky? 😉


    * Yes, yes, I know, I’m sure they use something a *lot* more advanced than just stopwatches for precisely timing the launch! Sundials maybe? 😉

  11. Samsam von Virginia

    Short launch window probably means the craft has very little maneuvering capability, and the trip is long, so initial conditions matter a lot.

    Although, you’d think burn time on the booster could compensate a bit.

  12. Grizzly

    This is going to be a long flight. I recall reading somewhere about orbital “manifolds”, using comparatively small nudges to get a spacecraft into a game of cosmic pinball, using the gravitation of objects in our solar system to move it into place. is this a similar concept?

  13. I am curious about the “instantaneous launch opportunities” on a mission to the Moon. I mean, if they were to launch 10 seconds late, they wouldn’t be able to compensate for the change in launch orientation? And if they can’t do that, why can they do it for a 39-minute difference?

  14. ASFalcon13

    @DennyMo, Samsam, and Ken B:

    The cruise trajectory is pretty sensitive to initial conditions, so the team has calculated two separate specific trajectories. The two windows 39 minutes apart correspond to these two trajectories, and the 39 minute gap gives plenty of time to recycle to the second attempt if the first attempt is scrubbed.

    The NASA press kit has lots of good info, and a nice diagram of the two trajectories on page 14:

  15. Dragonchild

    “You seek to launch the GRAIL!”
    “That is our quest. You know much that is public, O Phil.”
    “Yes, we’re, we’re looking for the launch window. Our quest is to launch the GRAIL.”
    “It is, yes, yup, yes, yeah.”
    “And so we’re, we’re, we’re, we’re trying to launch.”
    “We have been for some time.”
    “Uh, so, uh, anything you can do to, uh, to help, would be…very… helpful.”

  16. Messier Tidy Upper

    @ ^ DragonChild : I see what you did there. 😉

    Like . :-)

    What an eccentric performance! 😉

    Currently past launch time and holding due to high level winds.

    The rocket GRAIL may well get off the ground in twenty minutes or so hopefully; weather permitting.

  17. The GRAIL has been lifted! :-)

    Launched successfully so far – parking orbit for second stage currently.

    Nine minutes after launch.

    Click on my name for news update via NASA.

  18. Thea

    What about that Grail-shaped light? And the Frenchmen?


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar