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Angermann, Barbara; Hoffland, Shelly (ed.) / Wisconsin engineer
Volume 93, No. 2 (December 1988)

Lindell, Chris
The Hubble space telescope,   pp. 20-21


Page 20


TH E H U BBLE SPACE
TELESCOPE
by Chris Lindell
The Hubble Space Telescope to
be launched in the space shuttle in late
1989 or early 1990 will not be the first
space-based telescope, nor will it be the
first telescope that the University of
Wisconsin-Madison has had a major role
in developing. However, it will be the
most powerful, most useful, and most
capable telescope ever built-and not just
because it will be in space.
The Hubble Space Telescope
(HST) is unique in that it is the only
space telescope that takes advantage of
three benefits of being outside of the
earth's atmosphere: the sky is darker,
there is no partial absorption of non-
visible wavelengths due to the atmos-
phere, and there is no blurring of the
image by varying atmospheric refraction.
Professor Arthur Code of the Astronomy
Department likens this variation in
refraction of the earth's atmosphere to
looking through a swimiming pool to see
the bottom. The Hubble takes advantage
of its sophisticated optics, that other
space-based telescopes and earth-based
telescopes can't match, to see images
more clearly.
The capabilities of the HST will
be incredible. It will be able to see objects
ten times farther and 50 times fainter
than the best earth-based telescopes.
Additionally, the pointing accuracy and
angular resolution will be much im-
proved, allowing the HST to distinguish
details and separations between objects
ten times more clearly than telescopes on
the earth. The HST could see the light of
a candle at the distance of the moon, and
the separation between a car's headlights
from 2,000 miles.
"It is the best telescope ever
made," says Professor Code. After
looking at its capabilities, one can't help
but to agree.
The HST consists of a 2.4 meter
mirror, a Ritchey-Chretien type of
Cassegrain optical system, five on board
instruments, including the High Speed
Photometer, two solar panels, star
trackers, a rate gyro assembly, and
antennae. The whole package weighs
about 25,000 pounds and will fill the
entire Space Shuttle bay.
Once in orbit, the HST is in-
tended to have a lifetime of decades. The
complete design is modular, allowing
units to be repaired or replaced in orbit.
If necessary, the HST can be returned to
earth by the shuttle, repaired, and put
back into orbit. Also, new instruments
can be designed and substituted for
existing units.
Tracking Data Relay Satellites
(TDRS) and a Scientific Operation are
both integral parts of the complete
Hubble System. The TDRSs will be
placed in geosynchronous orbits, in
It will be able to see objects ten
times farther an 50 times fainter
than the best earth-based telescopes
which their positions are stationary with
respect to a point on the earth's surface,
and will allow constant communications
with the HST. The Space Telescope
Science Institute at Johns Hopkins
University will run the Scientific Opera-
tion. The operation will be based on
proposals submitted by interested
scientists to determine usage times in
order to maximize the HST's potential.
The University of Wisconsin has
many people working on the telescope.
UW researchers have been involved with
three of the five instruments on board,
including designing and making the
High Speed Photometer, the only part of
the telescope that was made at a univer-
sity. Professor Robert Bless of the
Astronomy Department is the Principal
Investigator for this project. Addition-
ally, Professor Code is working on the
wide-field and planetary camera in
conjunction with the California Institute
of Technology, and Astronomy Professor
Blair Savage has been involved in the
development of the high resolution
Wisconsin Engineer, December 1988
20


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