In my last post I introduced the
Hubble Space Telescope and its importance for planetary science and humanity in
general. In this post I would like to introduce the telescope in somewhat more
detail. I will take the Spacecraft apart, to introduce every aspect of
this significant apparatus individually.
As Hubble is the
first telescope in space, it was a forerunner in every sense. The outer-space
conditions are often severe and to achieve the best results possible
and to maintain the high performance of the telescope several spacecraft
support systems are in place to keep the telescope functioning. Over the
operation time of Hubble, it had experienced many major upgrades to ensure that
the telescope is always in compliance with the latest advancements of
technology. To introduce the technology behind it, I am going to separate the
spacecraft systems according to Housing,
Communication, Power, Computers.
The
Housing:
The Housing of the
telescope is basically the flesh and bones of the Spacecraft. It is the layer
that protects it from the severe conditions in space and the skeleton that
houses every single instrument. For example, solar winds and
sudden changes in temperature are very frequent conditions that can come
very sudden and unexpected. Therefore, the telescope has to be equipped with
the appropriate technologies to protect it.
The multi-layered
insulation (MSI)
on the telescope makes it appear as if it would be covered with Gold. It is a
layer that protects the telescope from thermal radiation and dust impacts. The
layer consists of many sheets, often with a solid layer, for example beta
cloth, which is a fireproof silica fiber cloth.
Another layer of
insulation was added during a servicing Mission in 2009. The New Outer Blanket
Layers (NOBLs).
This layer consists of sixteen thin layers of dimpled aluminized Kapton material
that are covered by an outer aluminized Teflon shell. This layer serves to
protect the telescope from radiation and prevents the inner systems from
overheating by simply reflecting the sun rays.
Under these layers
is the Skeleton of the telescope. It is a light-weight aluminum shell that holds
the parts together. It houses the optical devices and the supporting
instruments.
Power:
The Telescope is
powered by sun rays, as it could hardly be connected to Earth. As the telescope
has to power radio transmitters, computers and scientific instruments, it
requires much electricity. On the side of the tube (optics, main body), two
blue solar arrays are installed that are covered in a solar cell blanket. These
wing-like arrays convert sunlight into electricity. These arrays are designed
to be easily replaced by an astronaut. They can even be folded for shuttle
trips.
The telescope has
also batteries that ensure that it can operate while it orbits in Earth`s
shadow.
Communication:
Hubble receives instructions from the Flight Operations Team at Goddard Space Flight Center in Greenbelt, Md., and it performs the actions according to the instructions. With a very sensitive antenna it can capture the transmitted signs and send the data to Earth. It transmits the collected data to a Tracking and Data Relay System (TDSR) that consists of five satellites. These satellites then transmit the data to Earth. The telescope has to be in line of sight with at least on of the five satellites to transmit and receive information. While it is in line of sight of one satellite, scientist can perform direct changes in the pointing of the telescope and fine tune their observations.
(As the telescope
receives the commands well in advance, this is usually not necessary.)
In case a
satellite is not in sight, the telescope has a special data recorder that can
store the information until the satellite is in sight again.
Computers
and Automation:
In order to run
properly, the Hubble Telescope requires many computers and microprocessors.
It is equipped with two main computers that look like the belt
that surrounds the main body of the telescope. One of which is
responsible for the communication, the receiving and sending of data and
forwarding the instructions to the individual instruments. The other main
computer runs the gyroscopes, the pointing system, the optical devices (will be
explained in another post) and other system-wide functions. There are also
additional backup computers that keep Hubble safe in the event of a problem.
There are many
more small computers in the individual parts of the telescope that help to
collect the data, open and close the exposure shutter, direct the
rotation of the filter wheels and maintain the temperature of the instruments.
These smaller computers and microprocessors are all connected to the main
computers.
Further posts about the optical devices and how they function will follow.
Take care,
Harald
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