Did
you know?
Not
all payloads are carried to orbit in
the Shuttle's cargo bay. In-cabin payloads are carried in
the Shuttle's middeck. Cargo bay payloads are typically large
payloads, such as satellites and Space Station modules, which
do not require a pressurized environment. In contrast, in-cabin
payloads are generally smaller, and are not usually designed
for an unpressurized environment like the cargo bay.
Hubble
Space Telescope in a Shuttle payload bay.
The
European Space Agency (ESA) built Hubble's first two sets
of solar arrays. For the newest pair, ESA designed, developed
and tested the Solar Array Drive Mechanisms, which maneuver
the arrays to keep them constantly pointed at the Sun.
Scientists
and engineers at NASA's Goddard Space Flight Center in Greenbelt,
Md., devised the NICMOS Cryocooler, a state-of-the-art cryogenic
cooler that is expected to return NICMOS to active duty
and re-cool the NICMOS infrared detectors to about minus
203 degrees Celsius (minus 334 degrees Fahrenheit or 70
degrees Kelvin).
The
Advanced Camera for Surveys upon completion and testing
before installation into Shuttle Columbia's payload bay.
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STS-109
Payloads
Hubble
Space Telescope Servicing Mission
3B
The
Advanced Camera for Surveys
The Advanced Camera for Surveys, Hubble's new scientific instrument,
will give astronomers the opportunity to discover celestial
objects far beyond the reach of current instruments in a fraction
of the time, unlocking more of the universe's secrets. The new
camera, which is also known as ACS, is a large phonebooth-sized
instrument consisting of three different, specialized channels.
Each channel plays a unique imaging role, enabling ACS to contribute
to many different areas of astronomy and cosmology. It will
become Hubble's new workhorse, surveying far regions of the
universe, searching for extra-solar planets and observing weather
and other features on planets in our own solar system. With
its wider field of view, superb image quality and exquisite
sensitivity, ACS will take full advantage of Hubble's unique
position as a space-based telescope.
Hubble's New Solar Arrays
When STS-109 visits Hubble, space walkers will install new solar
arrays that will give the orbital observatory a new look and
boost its power. STS-109 astronauts will install the new arrays
during the mission's first two space walks.
Unlike
Hubble's first two pairs, which are so flexible that they roll
up like window shades, Hubble's newest solar arrays are flat,
rigid and they fold up. The new arrays have one-third less solar
cell area, but produce at least 20 percent more power than the
current set. The added power enables all the science instruments
to be powered and ready to operate simultaneously, allowing
for more discoveries in less time.
Also,
the new arrays, which are made of aluminum-lithium, are easier
for the astronauts to work around during servicing missions.
In addition, their smaller size decreases on-orbit drag and
slows the rate at which Hubble's orbit decays. Over time, all
low-Earth orbiting satellites feel the effects of atmospheric
drag and lose altitude.
The
NICMOS Cryocooler
During STS-109, the Near Infrared Camera and Multi-Object Spectrometer
(NICMOS), which has been dormant since January of 1999, will
receive a new cooling system called the NICMOS Cryocooler.
Installed
on Hubble in February 1997, NICMOS used infrared vision to explore
dark, dusty regions of space with precise optical clarity. Since
NICMOS operates at cold temperatures, it was encased in a container
filled with solid nitrogen ice to keep the detectors cold. A
small heat leak caused the nitrogen ice to consume more quickly
than planned.
The
Power Control Unit
The Power Control Unit, or PCU, is Hubble's power switching
station. As the central controller of the telescope's electrical
system, it regulates and distributes the power Hubble needs
to operate.
Reaction
Wheel Assembly
One of four reaction wheel assemblies, or RWAs, is scheduled
to be replaced during STS-109's second space walk. RWAs are
an important part of Hubble's Pointing Control Subsystem that
use rotational momentum to move the telescope from one target
to another and to keep it pointed steadily once the target is
acquired in the aperture of the observing scientific instrument.
Even though only three RWAs are required for scientific operations,
it was decided to add a spare RWA to the manifest of STS-109
because of the importance of the RWAs to the telescope's performance
and the amount of time between this servicing mission and the
next.
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