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Shuttle astronauts will visit
the Hubble Space Telescope

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for the final time in May 2009.

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In five bold and daring spacewalks,
they will upgrade Hubble's instruments,

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allowing it to continue making
remarkable scientific discoveries

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well into the next decade.

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This is the Hubblecast.

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News and images from the
NASA / ESA Hubble Space Telescope.

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Travelling through time and space
with our host, Dr. J

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EPISODE 28: Servicing Mission 4
a. k. a. Dr. Joe Liske.

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To scientists and the public alike,

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the NASA / ESA Hubble Space Telescope
is an icon of scientific progress.

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Although more than 100 space observatories
have been put into orbit over the years

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Hubble remains the best known.

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Its success story is based on amazing
scientific results and stunning images.

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But much of this was only
possible because once in a while

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astronauts went up there
and paid Hubble a visit.

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Welcome to the Hubblecast.

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I'm actually quite excited
because today we're going to look

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at the fifth, and final,
Hubble Servicing Mission.

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The NASA / ESA Hubble Space Telescope
is a remarkable feat of engineering

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that enable scientists to
produce the stunning results

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we have all come to love.

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From the very beginning, the design of
Hubble allowed the various instruments

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to be replaced over time,
as scientists on the ground

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developed new, more
powerful instruments.

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Now, a team of astronauts is
making one final journey to Hubble

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to give it a 100,000 orbit service.

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This is the fifth
servicing mission to Hubble.

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The first took place back in 1993 when,
in a series of landmark spacewalks,

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astronauts corrected
Hubble's nearsighted vision.

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Three further missions
in 1997, 1999 and 2002,

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replaced various instruments
and other components on Hubble.

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This fifth servicing
mission has two main parts:

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the first is to install
two new instruments

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and the second is to repair
two existing instruments

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that are already on-board Hubble:

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the ACS camera and
the STIS spectrograph.

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The first new instrument,
the Wide Field Camera 3,

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is essentially an
improved digital camera,

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just like the ones you and I may
use for our holiday snapshots,

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except that this one
boasts 16-megapixels,

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can observe in the ultraviolet,
visible and infrared regimes,

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and it weights several hundred kilos!

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The second new instrument is
the Cosmic Origin Spectrograph,

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which will work in the ultraviolet.

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Unlike cameras, a spectrograph
doesn't take images,

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instead it breaks up the light
into its constituent colours

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to show it spectrum,
a bit like a rainbow.

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Because the new Wide Field Camera
3 images in several colours,

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making it the firs panchromatic
instrument on Hubble,

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we can learn much about the
composition of distant objects.

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Ultraviolet light reveals hot
young stars burning brightly,

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yellow light reveals
clouds of hydrogen gas,

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and red light reveals the
glowing embers of oldest stars.

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By combining images
taken in each colour,

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astronomers can see
structure within galaxies

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and begin to learn how
it changes over time.

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A young proto-galaxy in the early Universe
blazes brightly in the ultraviolet.

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This light travels for 13
billion years to reach us,

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by which time this light is shifted into the
red and near-infrared part of the spectrum,

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and allows astronomers to see galaxies
in the early stages of evolution.

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The powerful new Cosmic
Origin Spectrograph, COS,

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will investigate the
gas between galaxies

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to learn more about
its chemical composition

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and the early growth of
stars in the Universe.

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It will do this by looking at how
the light from very distant quasars

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is absorbed as it
passes through the gas.

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Closer to home, this improved
spectrograph can also detect young stars

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burning hotter than our Sun,
embedded in the thick dust clouds

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that gave rise to their birth, clarifying
the phenomenon of star formation.

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The second task on this mission

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is going to be a huge
challenge for the astronauts.

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They have to repair two instruments
that are already on-board Hubble,

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but which haven't been working
properly for some time now.

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The problem is that these instruments

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were never designed to
be repaired in space.

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That means that some very
clever people have to invent

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new and dexterous tools to
help them carry out the repairs.

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The second problem is

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that it is actually not that
easy to play electrician in space.

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Astronauts wear really thick gloves.

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For them, any task is kind
of like trying to peel an egg

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with really thick oven gloves.

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Except for them, it
would be even harder.

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For example, they will have to
undo more than one hundred screws

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without losing any.

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I'm sure they'll be doing
a better job than me...

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The repaired STIS instrument
will obtain spectra from objects,

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but at different wavelengths
to the new COS instrument.

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For the first time, scientists
will be able to simultaneously

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see spectra from across a
wide range of wavelengths.

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Even with the introduction
of the new Wide Field Camera,

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the repaired ACS instrument
remains Hubble's most sensitive

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in the visible light range.

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It will continue to
capture stunning images

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and help scientists unravel
the mysteries of the Universe.

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In addition to the work on the instruments,
Hubble itself will also get a service.

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Just like your car, after 100,000 orbits

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Hubble needs the equivalent of an
oil change and a new set of tires.

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Astronauts will carry out extra
spacewalks to replace some parts

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that will keep Hubble flying
hopefully well into the next decade.

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They will also attach
a special mechanism

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that will allow a future robotic
spacecraft to dock with Hubble

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in order to steer it to a peaceful,
final resting place in the ocean.

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Upgrades to the power and guidance systems
will give Hubble a new lease of life.

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A rejuvenated Hubble
will allow astronomers

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to continue making remarkable
discoveries for many years to come.

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Impressive, isn't it?

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It looks like this servicing mission is
going to make Hubble better than ever.

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I'm already looking
forward to bringing you

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the exciting discoveries from
these instruments later this year.

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Look out for updates on the servicing
mission on our website at spacetelescope.org

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This is Dr. J
signing off for the Hubblecast.

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Once again, nature has surprised us
beyond our wildest imagination...

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Hubblecast is produced
by ESA / Hubble

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at the European
Southern Observatory in Germany.

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The Hubble mission is a project
of international cooperation

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between NASA and
the European Space Agency.