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[Music]

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the hubble space telescope has had five

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servicing missions since its launch in

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1990 from servicing mission 1 in 1993 to

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servicing mission 4 in 2009.

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wait what

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five servicing missions but the last one

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is called servicing mission four

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while it might seem strange at first

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there's a reason for that and that's

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because servicing mission 3 has a very

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interesting history

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originally scheduled for launch in

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mid-2000 hubble's third servicing

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mission was going to upgrade and

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refurbish the telescope just as the

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first two servicing missions had done

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before but in quick succession hubble's

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all-important gyroscopes begin to fail

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so why are hubble's gyroscopes so

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important

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hubble deputy project manager jim

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gellatik can explain so while we're

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turning hubble we need to know exactly

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which direction we're turning it so we

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use a sensor known as a gyroscope or a

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gyro

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they use the conservation of angular

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momentum to tell us if hubble is turning

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in which specific direction

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and how fast it's turning in that

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direction so essentially without the

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gyroscopes we have no way to know where

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hubble is pointing which for a telescope

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is kind of important

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in 1999 hubble needed at least three of

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its six gyroscopes to be running in

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order to do science and with only three

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gyros still functioning a hubble

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emergency was declared and servicing

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mission three was quickly split into two

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separate launches

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sm-3a's main priority would be switching

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out all the gyroscopes with new and

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improved versions while sm-3b was

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scheduled for a few years later and

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would work on the updates that hubble

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still needed but weren't as urgent

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due to this timing change the astronauts

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for sm-3a had less time to train for

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their important mission but they went

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into overdrive and were ready in time

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for their launch date of october 14

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1999 however delays caused by final

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inspections and wiring repairs on the

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shuttle continued to push the launch

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date deeper and deeper into the end of

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the year and then as if things couldn't

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get any worse in mid-november a fourth

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gyroscope on hubble failed hubble was

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put into safe mode and all science came

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to a screeching halt

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thankfully the hubble team had already

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decided to split sm-3 into two missions

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months earlier otherwise hubble would

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have been totally silent until the

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originally planned mid-2000 mission so

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after a few more delays due to more

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inspections rewiring engine replacements

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and bad weather the crew of sm-3a

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sitting in the cockpit of the space

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shuttle discovery was ready to launch

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the eight-day mission had three

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spacewalks planned the first was the

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all-important gyro switch-out there were

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a few minor problems that came up during

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the 8 hour 15 minute long space walk but

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by the end of the day hubble's gyro

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troubles were over

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the next two days had their own

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spacewalks updating hubble with a more

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advanced computer adding a new fine

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guidance sensor installing a new

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solid-state digital recorder and

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replacing hubble's old outer insulation

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with new panels in order to protect

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hubble's scientific equipment from

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getting too hot or too cold

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when all the work was finished hubble

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was released back into orbit on

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christmas day and as the crew of

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discovery landed at kennedy space center

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it became clear that this mission was a

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resounding success

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servicing mission 3b would also be a

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success later in march of 2002 followed

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by the fifth and final flight servicing

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mission 4 in may of 2009

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thanks to everyone involved with

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servicing mission 3a hubble was able to

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quickly get back on schedule with its

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groundbreaking science and continue

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forward with its mission of uncovering

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the mysteries of the universe

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i'm sure you know who i am

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you know today is the busiest day of the

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year for me i'm delivering presents to

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good girls and boys

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i heard the discovery was up in space

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working over the holidays so i decided

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to stop by

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and visit my astronaut fans and deliver

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presents because they've been good girls

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and boys

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it's a very busy time of the year

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and so i must be on my way

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but i would like to wish

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all the boys and girls around the world

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a merry christmas especially those ones

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down in houston and mission control at

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the kennedy space center which has done

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so much work during the holidays to make

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this fishing such a great success it's

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busy busy here so i gotta go merry