Hubble Space Telescope (HST) is a telescope orbiting the Earth at the
outer edges of the atmosphere. It is a space observatory in the Great
Observatories program. Named after Edwin Hubble, it was launched into
orbit in 1990 as a joint project of NASA and the European Space Agency.
Initial optical errors were corrected in 1993, and high-quality imaging
began in 1994. HST is projected to continue operating until 2009, when
funding is expected to be moved to the James Webb Space Telescope
the atmosphere has advantages because the atmosphere
obscures images and filters out electromagnetic radiation at certain
wavelengths, mainly in the infrared. By carrying diverse instruments
and dividing time between many astronomical projects from all over the
world, Hubble has contributed to an extraordinary variety of
astronomical discoveries. Among the most notable are the confirmation
of dark matter, observations supporting the current accelerating
universe theory, and studies of extrasolar planets.
description of Hubble
HST is located about 600 kilometers above the
ground, orbiting the Earth every 97 minutes.
Hubble masses about 11,000 kilograms, is 13.2
meters long, and has a maximum diameter of 4.2 m.
Two solar panels provide electricity, which is
mainly used to power the
instruments. Four large flywheels are used to orient and stabilize the
telescope. The telescope's infrared camera and multi object
spectrometer also need to be cooled down to minus 180 degrees Celsius
The spacecraft is rumored to be based in design
on the National
Reconnaissance Office's KH-11 reconnaissance satellite, with
differences in instrumentation focal point, and light sensitivity.
Evidence in favor of this theory include the fact that Hubble and
KH-11s were shipped in the same container.
a reflecting telescope with two
mirrors. The main mirror has
a diameter of about 2.4 m. The main mirror was erroneously ground into
a slightly incorrect shape; this is corrected by an optics package
known as the Corrective Optics Space Telescope Axial Replacement
(COSTAR). With COSTAR, the telescope can achieve optical resolutions
better than 0.1 arcseconds.
collected and focused by the telescope ends up in one of
several instruments. There are five instrument bays, designed to allow
instruments to be exchanged during servicing missions. Several such
replacements have been performed, taking advantage of new technology to
improve Hubble's capabilities. One of the instrument bays is occupied
The current (as
of 2004) complement of instruments is:
Near Infrared Camera and Multi-Object
Advanced Camera for Surveys (ACS)
Wide Field and Planetary Camera 2 (WFPC2)
Space Telescope Imaging Spectrograph (STIS),
which failed on August 3, 2004
Each of these
instruments has some capability as a spectrometer.
Additionally, the telescope's Fine Guidance Sensors (FGS) can be (and
have been) used for science.
Evidence of planets surrounding stars other
than the Sun was obtained for the first time with Hubble.
Observations with Hubble also showed that the
missing dark matter in our galaxy cannot consist solely of faint small
Some of the observations leading to the current
model of an
accelerating universe were performed using the Hubble space telescope.
The theory that most galaxies host a black hole in
their nucleus has been partially confirmed by many observations.
In December 1995, Hubble photographed the
Hubble Deep Field, a region
covering one 30-millionth of the area of the sky and containing several
thousand faint galaxies. A similar patch of southern sky was also
imaged and looked remarkably similar, strengthening the position that
the Universe is uniform over large scales, and that Earth occupies a
typical place in the Universe.Another Deep Field photograph was taken
In March 2004, Hubble photographed the Hubble
Ultra Deep Field. The
image is made from a million-second-long exposure, taken off and on
over a period of about three months.
The Future of
designed for 15 years of operation,
and it will end up
serving for 22.
Now the space
agency and the astronomy community have to sit down and
figure out what, if anything, should follow the Hubble. The James Webb
Space Telescope (JWST, formerly known as the Next Generation Space
Telescope, NGST) may replace the HST in 2012. However, the JWST is an
infrared telescope, while the Hubble covered the range from the near
infrared through the visible into the near ultraviolet.
the question are the breathtaking advances in
Earth-based astronomy since the Hubble was conceived. During the 1970s
when Hubble was designed, the conventional wisdom was that ground based
telescopes would never have the resolution of space telescopes because
the atmosphere seeing limited the resolution of ground telescopes. In
fact, microcomputer technology starting in the 1990s allowed for
adaptive optics which adjusts the mirrors continuously to compensate
for changes in the atmosphere.
This means that
there is not any need replace the Hubble to obtain
better astronomical imagery in the visible range. The new ground-based
telescopes can do the job, and even the most ambitious of them, like
the Keck in Hawaii and the Very Large Telescope (VLT) in Chile, are
much less expensive than the Hubble and much more sensitive to light.
This naturally is much easier to service and update. For example, the
VLT cost was roughly 1/7 of the HST cost, and gave the astronomic
community four 8.2 meters telescopes, with a resolution almost as high
as the Hubble.
The other side of
this, of course, is that ground based telescopes are
only just now approaching the abilities of a 20 year old 2.4 meter
space telescope. Much of the technology developed for these ground
telescopes is applicable to new space telescopes. A new space telescope
employing these new technologies and other general advancements made in
spaceflight over the last 20 years could once again revolutionize
are needed for wavelengths outside of visible
wavelengths. In particular, Hubble was eventually used largely for
observations of the near-ultraviolet, a frequency for which no new
telescopes are currently planned.
On January 29,
2004, NASA's Administrator said that that he would
review his decision to cancel the final servicing mission of the Hubble
Space Telescope due to public outcry and requests from Congress for
NASA to look for a way to save the Hubble Space Telescope. Adm. Hal
Gehman, chairman of the NASA board that investigated the Space Shuttle
Columbia incident would review and send his opinion to NASA according
to a letter sent from NASA Administrator Sean O' Keefe to Maryland
Senator Barbara Mikulski; Mikulski is the ranking Democrat on the
Senate subcommittee that oversees NASA's budget. Websites have been set
up dedicated to saving the Hubble Space Telescope.
noted that NASA's next generation space telescope,
named the James Webb Telescope is not scheduled for launch until 2010,
many years after the Hubble Space Telescope was originally expected to
cease functions. They also noted that about $200 million has already
been spent on two new instruments designed for the Hubble Space
Telescope and it might cost $300 million for a mission to return the
Hubble Space Telescope safely to the Earth. 
On July 13, 2004,
an official panel from the National Academy of
Sciences made the recommendation that the Hubble telescope be preserved
despite the apparent risks. Their report urged "NASA should take no
actions that would preclude a space shuttle servicing mission to the
Hubble Space Telescope."
On August 11,
2004, Sean O'Keefe requested the Goddard Space Flight
Center to prepare a detailed proposal for a robotic service mission. It
is expected that the proposal will take 12 months to produce - any such
mission, likely to cost in excess of $1 billion, will not take place
In early August
2004 NASA announced that MD Robotics of Canada would be
the sole bidder for the robot component of the rescue mission, given
its experience with Canadarm and the space station's Mobile Servicing
System. The last component of the system is the recently completed
Special Purpose Dexterous Manipulator which is nearly an
"off-the-shelf" answer to the requirements of the repair mission. http://en.wikipedia.org/wiki/Hubble_Space_Telescope http://en.wikipedia.org/wiki/Wikipedia:Copyrights