Author Topic: Discovery STS-31 – An Adventure Beyond the Mirror  (Read 192973 times)

Offline Ares67

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #40 on: 05/24/2013 12:36 am »

Offline Ares67

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #41 on: 05/24/2013 12:40 am »

Offline Ares67

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #42 on: 05/24/2013 12:41 am »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #43 on: 05/24/2013 12:42 am »
The ultimate “up” is just ahead for Rice astronomer Robert O’Dell

“Imagination creates reality.”

- Richard Wagner, German composer (1813 – 1883)


Since its inception nearly two decades ago, Rice University astronomer Robert O'Dell has followed the Hubble Space Telescope through its many ups and downs. The ultimate "up," the launch of HST aboard Discovery STS-31, is just ahead. "This is the biggest single thing in my professional life," said O'Dell, who became NASA's first chief Hubble program scientist in 1972, only to leave the post a decade later with the space telescope still years from launch.

Across the country, there are dozens like him, engineers as well as scientists, who have staked a major part of their careers on the success of the powerful orbiting observatory. In O'Dell's case, an association with NASA began in 1967. The space agency had suffered a serious setback in its historic race to the moon during January of that year, when three astronauts died in a fire aboard their Apollo capsule during a launch pad test. At that point the 30-year-old director of the University of Chicago's Yerkes Observatory, O'Dell became an adviser to the space agency.

Four years later, his experience with the construction of ground-based telescopes was sought by NASA for a more focused purpose, a program then known as the Large Space Telescope Project. By mid-1972, the space agency was finishing a feasibility study that concluded what visionaries had dreamed of a half century earlier: The Space Age would make it possible to place an observatory high above the bright city lights and the distortions of the Earth's atmosphere. O'Dell left his full professorship at the Chicago school and signed on as the space telescope program's chief scientist at NASA's Marshall Space Flight Center in Huntsville, Alabama, where the Hubble program was to be managed.

By mid-1981, NASA's Space Shuttle was finally aloft, and the space telescope was targeted for a 1983 launch. As the original launch date approached, O'Dell elected to reenter academia and pursue his research interests, which included using the telescope, rather than to continue building a career as a government scientist. He worked out an agreement with Rice University and NASA that would allow him to leave Marshall but continue to carry out his duties as the telescope's chief program scientist from Houston.

By late 1983, however, it was clear that the observatory would not be launched until late 1986. Delays had befallen the shuttle program and changes were occurring in the structure of the space telescope program within NASA. Those changes meant that the space agency needed a chief scientist in residence at Marshall. O'Dell declined an offer to return to NASA full time but did not sever his research ties to the space telescope. The separation turned out to be a wise one for O'Dell. The fatal Challenger accident on January 28, 1986, again grounded the space telescope. The launch slipped to late 1989 and eventually to April of this year. As discouraging as the shuttle disaster was, O'Dell believes the space agency used the recovery period wisely, improving both the powers and life span of the space telescope.

But, it also held some disappointment. In Challenger's aftermath, the space agency stopped taking civilians into space. Though that policy has been reversed for at least one approaching mission, O'Dell's chance to accompany the Hubble into orbit as a payload specialist was dashed. But, as the leader of one of seven teams of scientists who will get first crack at the use of the telescope, his ties and Rice's ties to the Hubble remain strong. His team will search for confirmation that Jupiter-sized planets may circle any of about 80 nearby stars, and attempt to further explain the role distant quasars played in the evolution of the galaxies. (The Houston Chronicle, Apr. 8, 1990 – edited)

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #44 on: 05/24/2013 12:44 am »
Peering toward the beginnings of the Universe

“I think it’s fair to say that the most important and exciting discoveries from the Hubble Space Telescope will be totally unexpected.”

- Edward J. Weiler, HST program scientist


(based on the “Hubble Space Telescope will peer toward beginnings of Universe” article by Martin A. Prisc, Countdown, April 1990, supplemented by passages from the “Hubble’s Promise” article in The Houston Chronicle, Apr. 8, 1990)

Imagine being able to travel back in time to witness the formation of the cosmos, and possessing the power to see more than what our eyes can detect. If one were able to observe Gamma rays, X-rays, and ultraviolet radiation, calculations could be made, such as the mass, orbit, and composition of celestial objects. But we would have to make such observations outside of Earth’s atmosphere, which soaks up such types of galactic emissions.

From such imagination evolved one of NASA’s greatest realties, the Hubble Space Telescope. HST will open our eyes to the Universe. “We’ll be like the near-sighted child in the classroom who is given a pair of glasses and at last can see what the teacher has been writing on the blackboard. Never before has humankind had the opportunity to increase its knowledge of the Universe more rapidly than we will in the 1990s,” says Dr. Lennard A. Fisk, NASA’s associate administrator for space science and applications. “We’re going to see some of the earliest objects in the Universe, and we’re going to learn how the Universe evolved out of its primordial uniformity into its present-day complexity.”

Modern astronomers compare Hubble's launch in significance to the moment 17th century Italian physicist Galileo Galilei raised a crude telescope to the night skies. "When Galileo first looked with his little telescope, no one knew that the moon had craters on it," notes California Institute of Technology astronomer James Westphal. "No one knew that Jupiter had bands across it, a red spot or little moons that circled around it.” Nor that the Universe is so immense that it holds millions of galaxies like our Milky Way, let alone celestial enigmas like supernovas, black holes and pulsars. With HST, information gathered from planets within our solar system and objects outside will allow scientists to piece together our own history. Hubble will probe not merely to the stars, but to the edges and origin of the entire Universe.

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #45 on: 05/24/2013 12:48 am »
EXPLORING OUR NEIGHBORHOOD

In our solar system, the HST will be able to monitor the turbulent conditions of the giant gas planets, providing the same types of views Voyager did when being at five-days distance from them. Hubble will be able to observe details of Jupiter’s cloud bands, probing why the bands change colors from time to time. At the same time, the images will not be limited to a quick look at a portion of the Jovian giant as was the case with flights such as Voyager.

The photometer will be able to determine the temperature and density of the upper atmosphere, and watch for changes that occur over time. Astronomers also hope that Hubble will get to see volcanoes erupting on one of its moons, Io, witness in detail a phenomena only seen on Earth previous to Voyager’s Io photos.

The next largest gas giant, Saturn, will also be observed with the same imaging qualities. Scientists will see clearer divisions between rings, cloud bands, and presenting the whole planet in every shot. Beneath its icy upper atmosphere Hubble may be able to determine cloud patterns, a feat Voyager wasn’t able to perform. Hubble will also provide more information regarding an unpredicted finding by Voyager in Saturn’s rings. Known as spokes, they are large, dark, rotating cylindrical objects which have somewhat puzzled scientists, and they hope Hubble will offer some insights.

Some of the most fascinating images of our solar system may come from viewing the outermost planets. As far as Earth-based scopes are considered, the outermost planets are merely dots on imaging paper. Hubble could present scientists with pictures of Uranus and Neptune in such clarity as telescopes on Earth show Jupiter.

The last stop in our neighborhood is Pluto, which little is known about because no missions have studied it with any detail. From Earth, astronomers can hardly detect its moon, let alone any details or even surface features. Hubble will send back pictures of Pluto comparable to a shot of the Earth’s Moon viewed with the unaided eye. By tracking the movements of Pluto and its moon Charon, scientists will be able to determine the pair’s composition, as well as their exact orbit.

“Lesser” planets, such as Mars and Venus, will get a wink from Hubble. Because Hubble will be able to view Mars for an extended period of time, it will be able to provide a detailed account of Mars’ changing polar caps. Another Martian feature, dust storms which occur throughout the entire planet, will be studied.

A new side of Mercury will be viewed by Hubble, which will send pictures of the hemisphere not photographed by Mariner 10. But the telescope will not view Mercury for a few years until controllers feel comfortable about the HST’s performance, since the tricky maneuver entails pointing the telescope close to the Sun. Hubble will wait for the planet to rise over the horizon, take a few shots, and then quickly move away before the Sun rises.


BEYOND THE EDGE

Despite the planetary harvest, Hubble’s full potential will be harnessed beyond the edge of our solar system. Deep space covers more than just distance; it spans time. While observing nebulas, galaxies, and other power sources one is looking back in time. Astronomers limited to Earth-based scopes know little about energy processes in celestial objects, as well as how stars are formed – and die as well. In comparison, a telescope on Earth can see about two billion light-years into space, while Hubble will go 14 billion light-years, a billion or two shy of when the cosmos was believed to be born.

“When you use the term ‘light-years,’ that’s the distance, but it’s also how much time it took the light to get here. So when you look at something at 500 million light-years, you’re looking at an object as it looked 500 million years ago,” says Dr. Edward J. Weiler, HST program scientist.

The Orion Nebula is of special interest to astronomers because it is a region where stars are born. Astronomers can only dream what this object – able to be viewed with the unaided eye – will look like with ten times greater resolution. Astronomers also want to take a look at the Owl and the Dumbbell nebulas to see if comets are active zooming around. The Hubble will also be able to view such objects in great detail, allowing researchers to search for planets orbiting any of 80 nearby stars, perhaps locating an Earth-like object where forms of life are feasible. One candidate, Beta Pictoris, is a "mere" 50 light-years from Earth. So far, astronomers have detected rings of lose matter circling a few of those stars and believe the material is in the process of accreting into planets. But even with Hubble's resolving powers, scientists say an observable planet would have to be at least the size of Jupiter.

Views of our own Milky Way will prove to be fascinating to astronomers as well. Imagine a photograph of two neutron stars revolving around each other at the rate of nearly a 100 times a second, and dwarf stars which are very faint and not easily visible from Earth. The Hubble will also show scientists stars in various stages of evolving, providing detailed information to understand the processes involved.

Globular clusters contain anywhere from 10,000 to 10 million stars, and have always been a hot-spot for studying stellar  evolution. All of the stars contained in a globular cluster are equal distance from each other, and the center contains so many stars astronomers cannot separate one star from the other. But Hubble will, and then scientists will be able to determine relative brightness of stars, and also be able to look at stars located in the center. And at the center of many such globulars, one of the greatest mysteries of the cosmos may lie – black holes.

Although no one has actually seen a black hole, they are the product of theories and predictions. “Black holes are very fashionable; they’re used to account for everything we don’t understand,” jokes Dr. Robert Bless, principal investigator for the HST high speed photometer. “It would be nice to pin the existence of one down.”

Black holes cannot be directly viewed because they are stars that have reached the very last stage of collapsing. They are so tight and compact because of immense gravitational forces that neither light and radiation can escape – but they cannot escape the view of the Hubble telescope. The high speed photometer will be able to determine whether or not a black hole exists by looking for bursts of radiation which change in length and brightness. These bursts are caused by material orbiting the hole at a fast rate and then get sucked in.

What the Hubble team hopes to measure is the radiation bursts as a piece of matter falls in, which is believed to be the signature of a black hole. One target of the black hole search will be M87, a galaxy 35 million light years away in the constellation Virgo. What has captured the interest of astronomers is the jet of material emerging from the center of M87. The jet suggests the presence of a massive, spinning black hole, theorists say. The rotation creates an electrical field with field lines that serve as paths for some of the material being sucked toward the black hole to be flung off in a jet. Using the Hubble's ultraviolet instruments, observers hope to "peel away" all of the interference that astronomers believe obscures M87's hot nucleus.

Supernovas are regions where black holes are also thought to be located. They are stars nearly five times that of our Sun, many of which explode after collapsing upon themselves. After exploding, many disperse their material into space, leaving behind a gigantic dust cloud. Within this cloud, new stars can form from the remaining dust. Many times instead of throwing all of its material into space, a dense core is left, which may become a black hole or a neutron star.

Scientists can hardly wait to point the telescope at active galaxies, characterized by a very bright center surrounded by hot clouds of gas moving at several hundred kilometers per second, indicating explosions are constantly occurring. What researchers want is information regarding the activity of the nuclei using the Faint Object Camera.

Long, thin jets of light are emitted from the center that can stretch out for several thousand light-years. Experts believe these emissions release energy from the center, but do not understand the nature of the energy’s source, and wonder if it is a black hole. Another interesting fact about active galaxies is that the amount of ultraviolet emission is often more than the output of all of the visible light.


INTO THE DISTANCE

As the HST peers into the distant Universe, and therefore back in time, it will look for evidence of galactic evolution. Currently, galaxies, no matter their age, all fall into the same basic forms. “We will be able to back up to ten billion light years and see what galaxies look like,” says Weiler. “The exciting thing is, we hope we see some evolution. We hope to see that they’re different, but we have no idea what we’ll see.”

Those differences could appear dramatic. “You can tell a lot of difference between 20-year-olds and 70-year-olds among people, so we hope we’re going to be able to tell a lot of difference between what galaxies looked like when they were only five billion years old instead of fifteen billion years old,” says Dr. James Westphal, the principal investigator for the HST Wide Field/Planetary Camera.

The Hubble telescope will try to determine the properties of another of the great forces in the Universe – quasars. Over 600 quasars have been discovered, the first in 1963. They give off more light than even large galaxies, and if one could harness the energy released by a quasar for one second, it would be enough to supply all of the electrical needs on Earth for a billion years.

They are also believed to reside on the edge of the Universe, and Hubble may be able to determine if the Universe is expanding or receding by observing redshifts or blueshifts in quasars. Redshifts have been noticed with several quasars, which appear red because they are moving quickly away from Earth, many at the rate of more than 30,000 miles per second. Known as the Doppler effect, the light from an approaching object will appear blue, while objects receding appear read. From current spectrograph measurements of many deep space objects, scientists theorize the Universe is still expanding because many appear red.

“Hubble could be a turning point in humankind’s perception of itself and its place in the Universe.”, NASA’s Lennard Fisk says, and will reveal the mind-numbing vastness of the Universe with its countless galaxies spread over billions of light years. "If you ask the proverbial man on the street to name a space science mission, the first one to come to mind is Hubble," says Fisk. "In fact it may be the only one to come to mind. It’s a recognition of humankind’s intrinsic curiosity about understanding the Universe in which they live, and a recognition that this is a mission from which they can expect fundamental discoveries. They could begin to understand creation. They expect to be rewarded, their curiosity satisfied by this mission.”

The Hubble's discoveries promise to rank second only to those man himself might uncover if human explorers were along for the visual journey to the far reaches of the Universe. The total impact of the information the HST will gather remains not fully known. Our imaginations form a limitation in trying to visualize what the HST will discover. Fisk says, “You can be sure that we can think of today will not be the fundamental discoveries of Hubble. Nature is very much more imaginative and very much more clever than we are – it’s bound to amaze us.” (JSC Space News Roundup, March 30, 1990; Countdown, April 1990, and The Houston Chronicle, Apr. 8, 1990 – edited)

Offline Ares67

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #46 on: 05/24/2013 12:51 am »
Science questions the Hubble Space Telescope will help answer

”It’s hard to predict what discoveries we’ll make. Clearly, we’ll understand a lot of the questions that perplex us today and develop new and more profound questions in the future. It really is like taking an observatory from the ground and putting it in space where you derive all the advantages of not having to observe through the atmosphere.”

 - Steven Hawley, astronomer and Mission Specialist, Discovery STS-31


The Hubble Space Telescope will be the largest, most complex, and most powerful observatory ever deployed in space. Stated technically, the space telescope should allow astronomers to probe the visible Universe with at least ten times finer resolution and with some fifty times greater sensitivity than any other machine built by humans. Stated non-technically, the space telescope will provide for astronomers on Earth a decidedly new vista – by allowing us to look far back into the past with unprecedented clarity.

When HST is declared operational, sometime in the fall of 1990 if the verification activities are accomplished satisfactorily, the astronomy team associated with the project will be able to finally begin their full-scale attack on some of astronomy and cosmology's toughest questions. These questions are much the same fundamental questions which the Renaissance philosophers, the Arab and before them the Egyptian and Mayan astrologer/astronomers faced. They are simple questions: How
big is the Universe? How old is the Universe?

Newer, but still simple, questions are based on our understanding of Edwin P. Hubble's pioneering work and that of the Russian mathematician Alexander Friedman and the corroborating evidence from Arno Penzias and Robert Wilson. These questions include: Will the Universe expand forever? What is the large scale structure of the Universe? And, is the Universe homogeneous on a large scale.

More difficult but allied questions pertain to why normal matter (baryons) exist at all. Why is matter seemingly smoothly distributed through the universe? How did structure (galaxies) arise from a smooth homogenous fireball (Big Bang)? Some of these cosmological questions give rise to further, more precise, questions. What is the Hubble Constant? Today's astronomical observations give numbers which vary by a factor of two. The Hubble Constant is a calculation of the rate at which space is expanding and is expressed in kilometers per second per megaparsec (3.26 million light years).

Another question facing today's astronomers is what is the age of the Universe. This is calculated by taking the inverse of the Hubble Constant . Today's numbers vary from 10 to 20 billion years of age. What is the deceleration parameter? This is a measure of whether the distant galaxies are receding at a slower rate than nearby (newer) galaxies and would indicate a finite Universe if the total pull of the matter in the Universe were sufficient to slow down the expansion and perhaps ultimately cause a recollapse.

The expansion of the Universe is controlled by the amount of matter per unit volume (density). If the density is high enough, the expansion of the Universe will eventually slow and reverse. If the density is not high enough then the Universe will expand forever. The measure of the density therefore becomes another critical element in our understanding the evolution of the Universe.

The Hubble Space Telescope will contribute to answering these questions in a variety of key observations. HST will be able to directly measure Cepheid variable stars out to 30 million light years. These stars are the mileposts by which distance is measured over vast distances. An accurate measure of Cepheid variables out to the distance of the Virgo supercluster (2,500 galaxies amassed together) will greatly extend reliable distance measurements more than ten times than can be routinely done from ground observations. HST will find Cepheid stars in a sample of about 50 galaxies to arrive at an accurate measurement of the Hubble Constant.

The Hubble telescope also will enable astronomers to determine the age of the Universe by accurately measuring stars at distances much greater than is now possible. Current cosmology has star formation occurring at a period about one billion years (or so) after the Big Bang when the temperature of the Universe cooled sufficiently to allow atomic hydrogen to form and begin condensing into stars. An accurate measurement of the ages of the oldest stars will set a minimum age for the Universe and therefore help constrain the Hubble Constant.

Because HST is ideally suited for the task of resolving faint galaxies at very high red shifts (a measure of recessional velocity and therefore distance), it will also help in determining the deceleration rate of distant galaxies. Before this technique can be applied, though, HST will have to add to our knowledge about such distance galaxies since current observations of these are so limited. Because such distant galaxies formed much longer ago than nearby galaxies, their intrinsic luminosity and color are not well understood which means they cannot reliably be used at the present as a milepost.

However, HST observations will contribute to the intrinsic understanding of these galaxies and subsequent observations based on new theories will allow potential use of these distant galaxies as measuring devices for studies of deceleration. By studying the motions of galaxies within clusters out to a distance of nearly 100 million light years, HST astronomers will be able to infer the mass of galaxies - both the light matter (stellar composition) and any dark matter components. The resulting density measurements can then be scaled up to compute the mass of the Universe as a whole.

Acquiring answers to cosmological questions are a major reason for the development and flight of the Hubble Space Telescope. There are, though, a great many questions in the realm of astronomy and astrophysics which HST will be addressing as well. A primary task for HST will be to trace the evolution of galaxies and clusters of galaxies. Since HST will be able to survey a volume of space nearly 100 times larger than can be surveyed with comparable resolution from the ground, HST will help give us a picture of what galaxies were like when the universe was only 35 percent of its present age.

Hubble's high resolution will allow a survey for extra galactic black holes. The imaging systems may be able to provide pictures of an accretion disk in nearby galaxies and HST spectrometers will enable us to measure the velocities of infalling gas thereby gauging the mass of suspected black holes. Hubble telescope's instruments should enable a breakthrough in our understanding of synchrotron jets which extend for hundreds of thousands of light years from the center of active galactic cores. For the first time, these jets will be seen in ultraviolet light. These observations will be matched with comparable resolution views taken with radio astronomy observations.

Some of the questions pertaining to galaxies, quasi-stellar objects (quasars or QSOs) and active galactic nuclei include: How soon after the Big Bang did galaxies form? How do galaxies evolve? What are the dynamics of galaxies in clusters? Do galaxies harbor massive black holes? What is the dark matter in a galaxy and how is it distributed? How important are galactic collisions in galaxy formation? What is the nature of starburst phenomena? What is the engine which powers quasars? What fuels the quasar engine? Are there new physics to be found powering the QSO engine? Do quasars represent a normal stage in galactic evolution?

Stellar physics questions to be addressed by HST include studying white dwarfs. White dwarf stars are keys to our understanding the stages of late stellar evolution. Hubble will aid in our present understanding of this stage in a star's life and answer questions such as, can stars re-ignite after having ejected much of their mass late in their life. At the other end of a star's life, HST will image circumstellar disks in star-forming regions to see how stellar activity affects the disks and perhaps deduce what conditions are right for planetary system formation.

Solar physics and solar system evolution are major fields of investigation for the HST astronomy team. Some of the questions HST will help answer in these fields are: What is the precise sequence of steps in star formation? What determines the rate of star formation? How common are jets and disk structures in other stars? What is the mechanism that triggers nova-like outbursts in double stars? What are the progenitor stars to supernovas? Do circumstellar disks show evidence of planet building? Do planets exist about other stars? How abundant are other solar systems? What is the meteorology of the outer planets and how does it change over time? What is the meteorology of Mars and what triggers the global summer dust storms? How do the surface patterns of Pluto change over time?

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #47 on: 05/24/2013 12:53 am »
COMPETITION

''We can't be sure what we'll discover when we go out there,'' says Dr. Peter Stockman, deputy director of the Space Telescope Science Institute. ''We often frame our understanding of what the space telescope will do in terms of what we expect to find, and actually it would be terribly anti-climactic if in fact we found what we expect to find. It's almost never been true in science that when you create a new capability to measure and to observe, that you in fact find what you expect to find.''

Competition to use the telescope is fierce. Had it been launched on schedule, the first 1,100 hours of observation time were to have been taken by the researchers who designed the telescope and its instruments. The institute used the unexpected delay in launching to solicit proposals from astronomers around the world for another 1,100 hours of observation time during Hubble’s first 12-month observing cycle. In April 1989 committees began selecting from among the 556 proposals received. Astronomers from over 30 countries were hoping to get their chance to use the HST.

John Bahcall, head of the Space Telescope Science Institute’s science programs selection office, commenting on the selection, says, “It is exciting to see the many excellent proposals and to think of the scientific discoveries that will soon emerge when the Hubble Space Telescope uncovers the mysteries of fundamental scientific questions.”

Criteria included the likelihood that an observation will produce scientific breakthroughs, whether the question has been pushed to the limits of ground-based observation and the demands that an observation would place on telescope time and other resources. Institute officials say the launching delay also allowed astronomers to refine their proposals, the result being an opportunity to choose what Dr. Stockman calls ''the best of the best.''

In all, 162 proposals were accepted following the intensive scientific peer review. Among the proposals selected are plans to search for black holes in neighboring galaxies, to get a better look at the most distant galaxies in the Universe, to probe the core of the Milky Way galaxy and to search for neutron stars that might trigger unusual gamma-ray bursts. (Eric J. Chaisson, “The Hubble Wars,” HarperCollins Publishers 1994; STS-31 Press Kit; New York Times, Feb. 19, 1989; Countdown, September 1989 – edited)

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #48 on: 05/24/2013 12:55 am »
Astronomer for a day

“The ancient Greeks considered astronomy one of the half dozen or so subjects required for the education of free men. I find, in discussions with first-graders and hippie communards, congressmen and cab drivers, that there is an enormous untapped reservoir of interest and excitement in things astronomical.”

- Carl Sagan (1934 – 1996)


(By Eric J. Chaisson)

The Hubble Space Telescope is not an extravagant toy just for erudite academicians and astute astrophysicists. Anyone can apply to use Space Telescope. Over the years, amateur astronomers have contributed greatly to our understanding of the heavens. Amateurs, in fact, have made many basic discoveries in the centuries following the Renaissance, and even in modern times provide aid to professional astronomers by scanning the skies nightly for transient phenomena – comets, supernovae, planetary storms, stellar outbursts.

The intent was to give an opportunity to backyard sky gazers who might have a fresh idea or novel approach that might not dawn on a more conservative PhD-level astronomer. We also wanted to tap into the vast audience of non-technical citizens who, because of astronomy’s universal appeal, at one time or another in their lives have looked to the skies and wondered about nature, to make a few of them an “astronomer for a day.”

Some of the hundreds of amateur proposals indeed reflected much original thinking: A New York high school teacher proposed to capture a momentary brightening due to melting frost or snow on a moon of Jupiter by precisely timing the opening of Hubble’s camera shutter with the moon’s appearance from behind its parent planet; a West Coast homemaker and mother of two children asked to use Hubble’s infrared capabilities to search for giant newborn planets around some nearby stars in such way that professionals had apparently not thought possible; a museum volunteer in San Francisco wanted to observe a potential large cloud of comets swarming around a relatively nearby star by waiting for the star to experience a nova outburst, thus irradiating the outlying comets; a free-lance oil prospector from New England suggested studying the peculiar chemical and magnetic properties of a prominent Big Dipper star so close to Earth that deep-space astronomers had bypassed it in their thinking.

These objectives were honored with less than an hour of Hubble time each, brief and clear observations that would have made Galileo proud.

Many proposals were outright rejected, including a few ludicrous ideas that made us wonder more about the proposers than the proposals: to photograph dark asteroids in our solar system by using a ground-based laser as a flash attachment, thus requiring Hubble to be programmed to take a snapshot exactly when the laser pulse reached the suddenly illuminated asteroid; to write a poem while observing a specific celestial object, in much the same way as had been done earlier while commissioning the Brooklyn Bridge; to use Hubble to observe the most distant object in the Universe and thus, somehow, to confirm humankind’s belief in paganism. – The latter proposer, when asked on the application form which of Hubble’s scientific instruments would be needed for the intended observation, replied, “It doesn’t matter, any one will do.” (Eric J. Chaisson, “The Hubble Wars,” HarperCollins Publishers, 1994 – edited)
« Last Edit: 06/08/2013 08:49 am by Ares67 »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #49 on: 05/24/2013 12:59 am »
A marvel of complexity

“…In the history of optical astronomy there have been only two great leaps forward in the clarity of humankind’s view of the Universe: Galileo’s telescope in the autumn of 1609 and the Hubble Space Telescope in the spring of 1990. I believed before launch, as I continue to do so now, that this dramatic advance in angular resolution is the single most important scientific justification for having built Space Telescope.”

- Eric J. Chaisson, “The Hubble Wars,” 1994


The Hubble Space Telescope is a little like a Nobel Peace Prize winner or basketball superstar Michael Jordan. It commands a unique respect. NASA's long-awaited space telescope is a marvel of precision and high-tech - a first cousin to the super-secret spy satellites that can read a license plate from hundreds of miles in space. But, pointed toward the vastness of space rather than the Earth, Hubble promises to function like a wondrous time machine.

Overall, the telescope has 10 times the resolution, or clarity, of ground-based instruments, the difference between being able to read the big letters on the second row of an eye chart and reading the bottom line. Your eyes can detect a standard flashlight bulb at about two miles. With the HST, you could see that flashlight bulb on the Moon, a distance of a quarter of a million miles. "The human eye can barely detect a firefly at 200 yards," said NASA astronomer Edward Weiler. "If your eye was as good as the space telescope, you could see that same firefly 10,000 miles away, a distance from Washington to Sydney, Australia."

Hubble, if stationed in Los Angeles, could spot a 6-foot tall astronaut standing by the shuttle launch pad more than 2,000 miles away in Florida. If the human eye could distinguish between two objects with the clarity of the space telescope, Weiler continued, "you could read this morning's Miami Herald headlines from the Kennedy Space Center, a distance of about 200 miles."

The HST weighs approximately 24,000 pounds (10.9 tons), which is three times heavier than any other astronomy satellite launched by NASA so far. It is 43.5 feet (13.3 meters) long, and 14 feet (4.3 meters) in diameter at its widest point. With the solar arrays deployed, total spacecraft diameter extends to 40 feet (12.2 meters). Roughly the size of a railroad tank car, the telescope looks more like two huge cylinders joined together and wrapped in aluminum foil. The two wing-like solar arrays extend horizontally from each side of these cylinders, and two dish-shaped antennas stretch out on rods above and below the body of the telescope.
« Last Edit: 05/24/2013 01:02 am by Ares67 »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #50 on: 05/24/2013 01:04 am »
MAINTENANCE-FRIENDLY

Many of the telescope's components are of modular design so they may be removed and replaced in orbit by astronauts. Though other spacecraft have received emergency repairs from shuttle crews, the HST is the first specifically designed for on-orbit servicing. Units may be pulled out and a replacement plugged in without disturbing other systems. Doors on the exterior of the telescope allow astronauts access to these modular components, called Orbital Replacement Units. Handrails and portable foot restraints make it easier for them to move about in the weightless environment while working on the telescope. A special carrier has been designed to fit in the orbiter's cargo bay to hold replacement parts and tools.

“One highly-significant thing about the Hubble Space Telescope is that it is designed to be maintained on-orbit by the shuttle after its initial deployment,” Mission Specialist Kathy Sullivan told British author Nigel Macknight in a 1988 interview. “As those of us that are directly involved with the telescope have looked in detail at what that will entail, and what boxes and components on it might most likely break down over the course of its lifetime, it has turned out that what’s needed is a very specific and unique set of tools.

We already have a general set of tools aboard the orbiter, of course, that we carry for use during spacewalks. It includes socket wrenches and even a ball-pane hammer, the normal sorts of tools that have a lot of general applicability if you’re creative. But when you go and open all the service ports and doors on the Hubble Space Telescope and look at the mountings for the high-gain antennas and the solar arrays and so forth that are protruding out from it, it turns out that you need to design some very special different tools to work in and around those areas.”

Sullivan continued, “Over the last three years, Bruce McCandless and I have been working with our tool designers here at Johnson Space Center, and with the people from the telescope project office over at Marshall Space Flight Center in Alabama, and we have now developed a set of 96 tools that constitute the toolbox for a maintenance and repair mission for the telescope.

We have the unique opportunity, before we deploy the telescope, of being able to go up to the actual flight vehicle – not just a full-scale mockup – and prove that this wrench will indeed fit onto that fastener, or that this doorway opens with enough clearance that we really can get these boxes out, and so on. Those sound like obvious, trivial little things, but of course we all bear in mind very strongly the minor little ill-fitting things that very nearly made it impossible to perform the specified tasks on the Solar Max satellite repair mission and the Palapa/Westar satellite retrieval.”

“Bruce and I have spent a lot of time in the water tank at Houston going through and refining the procedures associated with both deploying the telescope and then visiting it later to perform maintenance work,” said Kathy Sullivan. “We wanted to prove that the portable foot restraints that we carry to attach to the exterior of the telescope when we work on it do actually fit properly, and in locations that do allow you to reach the connector, or the box, or the instrument, that you have to work on.”

Maintenance in orbit is the most practical way to keep the equipment functioning and current during Hubble’s lifespan of 15 years or more in space with a minimum of down time. Some of the components such as batteries and solar arrays have a life expectancy shorter than 15 years and will need to be replaced from time to time. New technology will make it possible to design more sophisticated scientific instruments over the years. Several new generation instruments are already under development. In-orbit servicing allows worn parts to be replaced and new instruments to be substituted for the original equipment without the great expense, risk and delay of bringing the telescope back to Earth.

Astronauts will visit the space telescope every three to five years on servicing missions. In case of an emergency, special contingency rescue missions have been partially developed and could be mounted between the scheduled visits. The first regular maintenance visit is scheduled for 1993. “This is the first satellite specifically designed to be maintained on-orbit by the Space Shuttle vehicle,” explains Mission Specialist Bruce McCandless, who has been involved in the planning and development of those systems and procedures for the past ten years. “We can replace just about anything that isn’t welded onto the structure of the telescope. All of this is absolutely unique in the world. There is no other country, there is no other spacecraft system at this time and probably not for quite a number of years, that will have the technical capability and the management courage to commit a mission going up to a telescope, capturing it, bringing it aboard, repairing it and putting it back out there.”

On servicing missions, the Space Shuttle will rendezvous with the orbiting telescope. Astronauts will use the shuttle's Remote Manipulator System to pull in the observatory and mount it on a maintenance platform in the orbiter's payload bay. Astronauts will don space suits and go out into the bay to complete required maintenance. They may change out batteries or solar arrays, a computer, one of the scientific instruments, or any of the more than 50 units that can be replaced in orbit. The shuttle also may be used to carry the telescope back to its original orbital altitude if atmospheric drag has caused it to descend. Once the maintenance is finished, the telescope will be released once more as a free-flyer. A ground team reactivation will then take place so the telescope again can resume its exploration tasks.

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #51 on: 05/24/2013 01:05 am »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #52 on: 05/24/2013 01:06 am »
The support systems module consists of the exterior structure of the HST and the various systems that make it possible for the optical telescope assembly and the scientific instruments to do their job. The foil-like material with which the telescope is wrapped is actually multi-layer insulation, part of the telescope's thermal control system. The metallic silver surface reflects much of the direct sunlight which strikes the telescope to keep it from overheating. Tiny heaters are attached to many telescope components to warm them during the "eclipse" phase of orbit, when in the Earth's shadow.

Electrical power for the Hubble Space Telescope is collected from the Sun by the European Space Agency's 7.8 foot by 39.4 foot (2.4 by 12 meters) solar arrays, made by British Aerospace. These two fragile – 1/32 of an inch, less than a millimeter thin –  "wings" together contain 48,800 postage-stamp-size solar cells. They convert the Sun's energy to electricity during the portion of orbit that it is exposed to sunlight. Of the total power produced by the flexible plastic-backed solar array blankets – 4,100 watts – 2,400 watts are used by Hubble’s science and control instruments. The remaining power is used to recharge the telescope’s six Nickel Hydrogen batteries which provide electricity during eclipse.

Also included in the support systems module are the computer which controls the overall spacecraft; high-gain antennas which receive ground commands and transmit data back to Earth; the electrical power system; the structure of the telescope itself and its mechanical parts; and the safing system, designed to take over control of the telescope to protect it from damage in case of serious computer problems or loss of communication with ground controllers.
« Last Edit: 05/24/2013 01:09 am by Ares67 »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #53 on: 05/24/2013 01:11 am »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #54 on: 05/24/2013 01:12 am »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #55 on: 05/24/2013 01:15 am »
OPTICAL PERFECTION

The optical telescope assembly contains the two mirrors which collect and focus light from the celestial objects being studied. The aluminum/magnesium flouride-coated 94-inch primary mirror, weighing 1,825 pounds, is located near the center of the HST. To reduce weight, the front and back plates are fused to a honeycomb core. The primary mirror will be able to resolve objects nearly ten times greater than Earth-based telescopes. Made of precision-ground glass with an aluminum reflecting surface, it is the smoothest large mirror ever made.

“The Hubble Space Telescope’s mirror – it has been said, and it’s actually true – is the finest mirror ever produced by humans. It’s so accurate that no part of its surface deviates by more than about a millionth of an inch over the entire 94 inches,” Dr. Edward J. Weiler, HST program scientist, says. If the surface of the Earth were as smooth as the telescope's mirror, Mount Everest would be about 5 inches high. In contrast, an ordinary eyeglass lens scaled up to that size would have mountains as tall as the Empire State Building. The four-millionth of an inch coating, if removed from the mirror and thrown into the air, would float for days like a fine mist.

The 13-inch secondary mirror is located 16 feet in front of the primary mirror. It is set far enough inside the open end of the telescope to assure that stray light does not interfere with the image being studied. In addition, three black cylinders called baffles surround the path of light to block out unwanted rays.

The two mirrors must remain in precise alignment for the images they collect to be in focus. But the space environment is a hostile one. The space telescope will experience wide variations in temperature as it passes from the sun to shade portions of its orbit. Expansion and contraction from the temperature extremes could easily cause the mirrors to go out of focus. Therefore, the mirrors are made of a special kind of glass formulated to resist that expansion and contraction. The telescope's insulation blankets and solar-powered heaters will maintain them at 70 degrees Fahrenheit.

In addition, the mirrors are held a precise distance from one another by an extremely strong but lightweight truss structure. The truss is made from graphite epoxy, a material also chosen for its resistance to expansion and contraction in temperature extremes.

During observations, light from a celestial source travels through the tube of the telescope to the large primary mirror. It is then reflected from the primary mirror back to the secondary mirror. From there, the beam narrows and intensifies, then passes through a hole in the center of the primary mirror to a focal plane where the scientific instruments are located.

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #56 on: 05/24/2013 01:20 am »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #57 on: 05/24/2013 01:22 am »
The Hubble Space Telescope's scientific instruments are the Wide Field/Planetary Camera, the Faint Object Camera, the Goddard High Resolution Spectrograph, the Faint Object Spectrograph, and the High Speed Photometer. The fine guidance system, in addition to being used for pointing, also performs scientific measurements and is sometimes called the sixth scientific instrument.

Mounted on a focal plane almost five feet behind the primary mirror, these scientific instruments will furnish astronomers with a wide range of information about the stars and galaxies they study. Each instrument is contained in a separate module. The telescope's digital images and other data will be beamed down to scientists on the ground at up to 1 million bits per second - fast enough to transmit the contents of a 30-volume encyclopedia in 42 minutes. Despite their sensitivity, the telescope's two cameras, two light-splitting spectrographs and one photometer require only 110 to 150 watts of power - the amount used by a typical three-way light bulb.

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #58 on: 05/24/2013 01:27 am »

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Re: Discovery STS-31 – An Adventure Beyond the Mirror
« Reply #59 on: 05/24/2013 01:30 am »
SCIENCE INSTRUMENTS

The Wide Field/Planetary Camera (WF/PC), pronounced “wiffpick,” developed by the California Institute of Technology and built by NASA’s Jet Propulsion Laboratory, will be used to investigate the age of the Universe and search for new planetary systems around young stars. It can compare near and far galaxies and observe comets such as Halley's comet, which we previously could only view every 75 years. As its name implies, the WF/PC can be used in two different ways. In its wide-field mode, its field of view will allow it to take pictures of dozens or even hundreds of distant galaxies at once. In the planetary mode, it will provide close-ups of all the planets in our solar system except Mercury, which is too close to the sun for safe pointing. Theoretically, using the WF/PC, you could read a license plate 30 miles away.

The WF/PC can observe larger areas of the sky and more different forms of light (from far ultraviolet to near infrared) than any of the other science instruments. It will also produce a greater volume of information for analysis than any of the others. Though its field of view is greater than that of any other Hubble instrument, the "wide field" in this camera's name may be a little misleading. Typical wide-field cameras at ground observatories have a field of view of around 5 degrees. This camera's is only 2.67 arc minutes. It would take a montage of about 100 "wide-field" images to get a picture of the full moon. However, the narrower field of view allows much better resolution of far-away objects.

Although it will focus on an even smaller area than its wide-field counterpart, the Faint Object Camera (FOC) will extend the reach of the HST to its greatest possible distance and produce its sharpest images. It will be able to photograph stars five times farther away than is possible with telescopes located on the ground. FOC will photograph objects too faint to be noticed by any of the other Hubble instruments. It contains an electronic image intensifier and four filter wheels.

Many stars and galaxies, now barely perceptible, will appear as blazing sources of light to the FOC. The camera will intensify images to a brightness 100,000 times greater than they were when received by the telescope –  the same as increasing the light of a candle flame to the brightness of the noon Sun. Then a television camera will scan the intensified images and store them in the camera's memory for transmission to the ground.

The FOC, being able to expose the picture of a faint object for ten hours, will be used to help determine the distance scale of the Universe, peer into the centers of globular star clusters, photograph phenomena so faint they cannot be detected from the ground, and study binary stars (two stars so close together they appear to be one). It is part of the European Space Agency's contribution to the space telescope program.

Two spectrographs are also included in the HST's group of scientific instruments. A spectrograph does not take a photograph of the image it sees. Rather, one could say it takes its chemical "fingerprint." A spectrograph separates the radiation received from an object according to wavelengths, much as a prism splits visible light into colors. Every chemical element produces its own individual pattern on a spectrogram. So when the "fingerprint" of a certain element shows up on the spectrum, scientists know that element is present in the object being viewed. Scientists use spectrographs to determine the chemical composition, temperature, pressure and density of the objects they are viewing.

The Faint Object Spectrograph (FOS), developed by the University of California and manufactured by Martin Marietta, will be used to analyze the properties of extremely faint objects in both visible and ultraviolet light. Using a mirror system, it will be able to isolate individual light sources from those surrounding them at very great distances. It has such great resolution that it could tell the difference between a car’s left and right headlight from a distance of 2,500 miles, about the same from Atlanta to San Francisco.

The FOS is equipped with devices that can block out light at the center of an image so the much fainter light around a bright object can be viewed. It will study the chemical properties of comets before they get close enough to the Sun for their chemistry to be altered, as well as probing to see what the mysterious quasars are made of. This instrument will offer comparisons of galaxies that are relatively near Earth with those at great distances, helping researchers determine the history of galaxies and the rate at which the Universe is expanding.

The Goddard High Resolution Spectrograph (GHRS), though its work is similar to that of its faint object companion, has a specialized job. It is the only science instrument entirely devoted to studies of ultraviolet light. Its detectors are designed to be insensitive to visible light, since the ultraviolet emissions from stars are often hidden by the much brighter visible emissions. The "high resolution" in this instrument's name refers to high spectral resolution, or the ability to study the chemical fingerprints of objects in very great detail.

The combination of this spectral resolution with the high spatial resolution of the cameras will allow scientists to determine the chemical nature, temperature, and density of the gas between stars. Its investigations will range from peering into the center of far-away quasars to analyzing the atmospheres of planets in our own solar system. GHRS will be searching for the chemical element deuterium, believed to be a major product of the Big Bang. To find this element, it will focus at supernova explosions and cometary gasses.

The High Speed Photometer (HSP), a relatively simple but precise light meter built by the University of Wisconsin, will measure the brightness of objects being studied, as well as any variations in that brightness with time, in both the visible and ultraviolet ranges. The photometer will be able to study the smallest astronomical objects of any of the telescope's instruments. One of the photometer's tasks will be to look for clues that black holes exist in binary star systems. Variations in brightness would occur as one star revolves around the other. Irregularities in that variation might indicate that matter is being lost to a black hole – an object so dense that nothing, not even light, can escape from it. The photometer will also provide astronomers with an accurate map of the magnitude of stars.
« Last Edit: 05/24/2013 01:30 am by Ares67 »

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