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hi I'm Nathaniel Thompson and I'm Dan

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cota and this is your building curiosity

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update we're standing here in front of

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the large spin table this is the machine

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that we use to measure the mass

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properties of the Curiosity spacecraft

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mass properties describe the way an

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object moves through space there's three

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masts properties that we measure mass

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center of gravity and the rotational

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inertia the rotational inertia tell us

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how the matter is distributed and spread

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out it affects how easy it is to spin

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the object and also how the object will

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wobble as its spun during the cruise

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phase as we're flying through space to

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Mars the vehicle is rotating and it's

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using a camera star scanner to navigate

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by taking pictures of the stars if we're

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rotating and wobbling we can't get a

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good track on the stars and we won't be

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able to properly navigate we also use

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our antennas to communicate back with

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earth again if we're wobbling too much

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we can't correctly communicate with

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earth the principal over a rotational

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inertia test is very similar to the way

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you have your tires balanced at your

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local mechanic the mechanic will rotate

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the tires very quickly on a machine that

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measures the amount that it wobbles they

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will then put balancing weights on the

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tire until it spins smoothly this is

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exactly the way we spin and balance our

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spacecraft now we know what mass

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properties are how do we go about

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measuring them to do that we need a

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special machine called a spin table this

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is a miniature version of the large

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table that we use to measure our

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spacecraft the table floats on a cushion

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of air there are sensors inside the body

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of the table that measure the balance of

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the rover on top of the table kind of

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like a seesaw we've done a lot of

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testing already here at JPL now we're

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packing up our table and getting ready

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to ship it to Florida in Florida will be

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doing the most exciting test of all a

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full spacecraft with fuel loaded on the

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table

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measuring it to make sure it's ready for

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launch i'm nathaniel thompson and i'm