adding time to the school day in order to focus on reading and math

Almost half the nation’s school districts have significantly decreased the daily class time spent on subjects like science, art and history as a result of the federal No Child Left Behind law’s focus on annual tests in reading and math, according to a new report released yesterday.
The report, by the Center on Education Policy, a Washington group that studies the law’s implementation in school districts nationwide, said that about 44 percent of districts have cut time from one or more subjects or activities in elementary schools to extend time for longer daily math and reading lessons. Among the subjects or activities getting less attention since the law took effect in 2002 are science, social studies, art and music, gym, lunch and recess, the report said.
The report, based on a survey of nearly 350 of the nation’s 15,000 districts, said 62 percent of school districts had increased daily class time in reading and math since the law took effect.
Within a year of the law’s implementation, teachers and their associations were reporting that schools and districts were suggesting or requiring that they spend more time on reading and math to improve test scores, and that they cut back time spent on other disciplines.
The narrowing of the nation’s elementary school curriculum has been significant, according to the report, but may not be affecting as many schools as previously thought.
A report that the center issued in March 2006, based on a similar survey, gave one of the first measures of the extent of the narrowing trend. It said 71 percent of districts had reduced elementary school instruction in at least one other subject to make more time for reading and mathematics. That finding attracted considerable attention, with many groups opposed to the law decrying the trend.
The law’s backers, including Secretary of Education Margaret Spellings, argued that the intensification of English and math instruction made good sense on its own because, they said, students who could not read or calculate with fluency would flounder in other subjects, too.
The center’s new report raises the question of how to explain the considerable discrepancy between last year’s finding, that 71 percent of districts had reduced instructional time in subjects other than math and reading, and this year’s, which gives the number as 44 percent.
Jack Jennings, the center’s president, said in an interview that the discrepancy was a result of a change in the wording of the questionnaire. Last year’s survey asked districts to say whether they had reduced instructional time in subjects other than reading and math “to a great extent,” “somewhat,” “minimally” or “not at all.” Districts that reported even minimally reduced instructional time on other subjects were included in the 71 percent, along with districts that carried out more substantial changes, Mr. Jennings said.
This year, the center listed English/language arts and math as well as social studies, art and music, science and other subjects on the survey, and asked districts whether class time in each had increased, stayed the same or decreased since the law’s enactment. In a second column, the survey asked districts to indicate the number of minutes by which instructional time had increased or decreased.
Districts that made only small reductions this year, 10 minutes a day or less, in the time devoted to courses other than reading or math, may have chosen to report that instructional time had remained the same, Mr. Jennings said. On last year’s survey, the same districts may instead have acknowledged reducing the time, while characterizing the reduction as minimal, he said.
According to the new survey, the average change in instructional time in elementary schools since the law’s enactment has been 140 additional minutes per week for reading, 87 additional minutes per week for math, 76 fewer minutes per week for social studies, 75 fewer minutes for science, 57 fewer minutes for art and 40 fewer minutes for gym.
In a statement, Secretary Spellings said the report’s scope was “too limited to draw broad conclusions.”
“In fact,” she said, “there is much evidence that shows schools are adding time to the school day in order to focus on reading and math, not cutting time from other subjects.”

Robotic ankle research gets off on the right foot

An Army veteran who lost part of his leg in Iraq walked with more spring in his step Monday as he unveiled the world's first robotic ankle -- an important advance for lower-limb amputees that was developed by a team at MIT.

Garth Stewart, 24, who lost his left leg below the knee in an explosion in Iraq, demonstrated the new powered ankle-foot prosthesis during a ceremony at the Providence, R.I., Veterans Affairs Medical Center. Stewart walked in the device, which, unlike any other, propels users forward using tendon-like springs and an electric motor. The prototype device reduces fatigue, improves balance and provides amputees with a more fluid gait. It could become commercially available as early as the summer of 2008.

MIT Media Lab Professor Hugh Herr and his team of researchers developed the ankle-foot. Herr, NEC Career Development Professor and head of the biomechatronics research group at the Media Lab, is a VA research investigator. He is also a double amputee who tested his invention: "This design releases three times the power of a conventional prosthesis to propel you forward and, for the first time, provides amputees with a truly humanlike gait," Herr said.

"It's wild," he said, "like you're on one of those moving walkways in the airport."

Because conventional prostheses only provide a passive spring response during walking, they force the amputee to have an unnatural gait and typically to expend some 30 percent more energy on walking than a non-amputee. The new ankle is light, flexible, and -- most importantly -- generates energy for walking beyond that which can be released from a spring alone.

This is accomplished through a device equipped with multiple springs and a small battery-powered motor. The energy produced from the forward motion of the person wearing the prosthesis is stored in the power-assisted spring, and then released as the foot pushes off. Additional mechanical energy is also added to help momentum.

Herr created the device through the Center for Restorative and Regenerative Medicine (CRRM), a collaborative research initiative that includes the Providence VA Medical Center, Brown University and MIT. The center's mission is to improve the lives of individuals with limb trauma through tissue restoration, advanced rehabilitation and new prosthetics that give amputees - particularly war veterans - better mobility and control of their limbs and reduce the discomfort and infections common with current prostheses.

To achieve this goal, the center funds a team of researchers with expertise in tissue engineering, orthopedics, neurotechnology, prosthetic design and rehabilitation. The aim is to bring these complementary techniques together to create "biohybrid" limbs composed of biological and man-made materials - a melding of man and machine.

To meet this goal, the VA has provided an additional $6.9 million to construct a state-of-the-art rehabilitation research building that will house the center on the campus of the Providence VA Medical Center. Construction begins this fall.

"A major goal of the center is to develop artificial limbs that perform like biological ones," said Professor Roy Aaron, M.D., of Brown University, director of the CRRM. "Hugh Herr and his team have met that goal - and done so successfully. This device is a major step forward for Garth Stewart and other amputees."

Joel Kupersmith, M.D., chief research and development officer for VA, said a top priority for the department is providing state-of-the-art prosthetic care for veterans - especially those returning from Iraq and Afghanistan. VA research, he said, is integral to this effort.

"The robotic ankle is a sterling example of how our leading-edge research improves veterans' lives," Kupersmith said. "Up to now, prosthetic devices have not been able to duplicate the complex functions of our feet and ankles as we walk and run. The ingenious computerized design of this new prosthesis changes all of this, as it constantly 'thinks' and responds, allowing the person to walk or run in a more natural and comfortable way."

Michael E. Selzer, M.D., director of Rehabilitation Research and Development for VA, agreed: "Hugh Herr and his Media Lab group are well-known for their scientific ingenuity and creativity on behalf of amputees. This new technology represents rehabilitation research at its finest, and is yet another milestone in VA's long history of outstanding achievements in this area."

AOL to buy Web ad tracker Tacoda

Time Warner Inc. unit, agreed to buy closely held Tacoda for technology to place Internet ads based on consumers' online behavior. New York-based Tacoda Inc. plans to track how users view AOL and its partner websites to come up with more targeted ads tied to those preferences. The purchase price is $200 million to $300 million, Dulles, Va.-based AOL said. The acquisition would be the third this year aimed at boosting AOL's advertising to make up for declining revenue from Web access service.

China has a strong local talent pool. People are well educated and very passionate about technology and innovation

For China's youngest citizens, it is an eye-popping morning. It is jab day at a clinic in Beijing.
Parents line up in the corridor, each holding onto a worried-looking child. Behind a curtain, there is a nurse wearing a face mask. Beside the nurse is a pile of syringes.
One boy, Lu Junran, starts to shriek. His father holds him and strokes his hair, and the nurse gives the injection.
The vaccines this clinic uses have been developed by the Chinese company Sinovac.
China hopes that companies like Sinovac can help the country take an important step - from "Made in China" to "Invented in China".
China does not want to make other people's products forever. It plans to start inventing products of its own.
After all, that is what China used to do.

China is the country that gave the world gunpowder, paper and the compass.
But in recent centuries, its inventions have dried up. Now it wants to start innovating again.
Sinovac's headquarters is in an industrial park on the outskirts of Beijing. Photos in the lobby show the company's scientists taking President Hu Jintao around the laboratories.
In its labs, Sinovac scientists are trying to pioneer a bird flu vaccine - something that no other country has managed to do.
"We can't just be a factory for the world," says Sinovac's boss, Yin Weidong. "There's a huge market out there. We have to start designing our own products."
Mind-bending problems
Since 1999, Chinese spending on research and development has grown by 20% every year.
Hu Jintao has set a research and development target of 2.5% of gross domestic product by 2020.
The country's spending is now starting to have a global impact.
The Organisation for Economic Co-operation and Development (OECD) says that China has now overtaken Japan's research and development spending.
In seven years time, China may also overtake the world leader, the United States.
So multinational firms are now betting that the long-term future of innovation may lie in China.
Hundreds of companies have opened research centres in Beijing and Shanghai.
Intel has its own compound in a skyscraper in Beijing, where dozens of young researchers doodle on notepads or write incomprehensible programmes onto their computer screens.
Intel's strategy is simple - sign up the best young brains in China and then get them to have a go at some mind-bending problems, such as face processing imaging, machinery application on video retrieval and ultra-mobile devices.
"We believe that China has great potential in innovation," says Yimin Zhang, who runs Intel's Application Research Lab.
"China has a strong local talent pool. People are well educated and very passionate about technology and innovation."
And there are more and more of them. Every year more than 20,000 Chinese students obtain their doctorates. Some choose to work abroad, but many are now being encouraged to stay in China.
This new generation has its orders - to start inventing.
That is quite an ambition for a country built on repetition, copying and obedience.

Promising new prototype called the BioSuit: a sleek, white, clingy outfit Revolutionizing Outer Space Style,

For 40 years astronauts have been lumbering around space in the same heavy, energy-sapping suits — and that is what Dava Newman, professor of aeronautics, astronautics and engineering systems at the Massachusetts Institute of Technology, wants to change. Newman and her team of researchers have just unveiled a promising new prototype called the BioSuit: a sleek, white, clingy outfit, whose revolutionary design has the potential to make astronauts feel as agile and au courant as Spider-Man.
The new anti-spacesuit spacesuit is made of an elastic, skintight material, lightweight enough to allow astronauts to walk, run or even scale mountains on a moon or planet's surface — acts that are physically impossible using NASA's current Tin Man-like designs. The form-fitting style of the new suit doesn't just make for a beguiling photo op; it also keeps astronauts alive by creating what scientists call mechanical counter pressure, which balances out the vacuum pull of space. The spacesuits worn today use gas pressurization — they create a small Earth-like atmosphere inside the suit, which exerts the appropriate force on the astronaut's body. The system works, but many scientists consider it to be out of date because it requires bulky equipment and a life support system that weighs almost 300 lbs. "These suits are fine for space shuttles or stations," Newman says. "But not for exploration." In fact, estimates show that astronauts typically end up expending about 70% to 80% of their energy just moving around in their suit.
The new suit creates the same kind of pressurized environment, simply by wrapping layers of specially patterned nylon and Spandex fabric tightly around the body, a method that Newman's been working on for seven years. When the material is properly wrapped, according to maps of the wearer's body in motion, it creates a mobile, skeleton-like shell that protects and supports the astronaut. When the new suits roll out, each one will be tailored to the individual astronaut and slipped on like a snug wetsuit — a "second skin," says Newman. One kink she's still trying to work out: figuring out a way for the suits to sustain enough counter pressure. To work, the BioSuit needs to exert close to one-third of the pressure exerted by the Earth's atmosphere, or 30 kilopascals (kPA). So far, the suits have consistently given off only 20 kPA. The researchers aren't sure what the problem is yet, but they suspect it has something to do with the suit's pattern.
Aside from its more appealing profile and wearability, Newman says, the BioSuit will likely be safer for astronauts than the old-style suits. Currently, when an astronaut's suit is punctured, he or she has to go back to the base to undress and decompress. With the new suits, astronauts could simply slap a patch over the tear. The BioSuit also provides a level of resistance that helps the body maintain muscle mass, since astronauts lose about 40% of their brawn during space travel. So, if the suit doesn't end up making it to Mars, researchers say it could possibly be used by athletes in training.
Newman estimates that the new suit, funded in part by the NASA Institute for Advanced Concepts, will be ready in about 10 years — probably about the same time NASA will start sending people to Mars and other moons. "If astronauts ever want to take more than a few steps and explore, they will need new suits," says Newman.

LHC- My Space & Earth: Dinosaurs coexisted with their ancestorsStory Highlights

LHC- My Space & Earth: Dinosaurs coexisted with their ancestorsStory Highlights

LHC- My Space & Earth: Experts have recreated the final, fateful moments leading up to last year's Black Hawk helicopter crash off Fiji.

LHC- My Space & Earth: Experts have recreated the final, fateful moments leading up to last year's Black Hawk helicopter crash off Fiji.

Experts have recreated the final, fateful moments leading up to last year's Black Hawk helicopter crash off Fiji.

Defence department experts have recreated the final, fateful moments leading up to last year's Black Hawk helicopter crash off Fiji.
It emerged at the Sydney military board of inquiry into the crash that given the conditions of the helicopter's approach to land on HMAS Kanimbla, there was insufficient power to slow its descent and lessen its impact with the warship.
Through a combination of 3D computer modelling, helicopter simulator trials and the analysis of the Black Hawk's flight data recorder (FDR), experts also were able to rule out engine failure as a cause of the crash.
The expert witnesses from the Defence Science and Technology Organisation (DSTO) gave evidence as part of the inquiry into how the helicopter failed to negotiate a landing on the deck of the Kanimbla and plunged into the sea last November.
The pilot, Captain Mark Bingley, and SAS Trooper Joshua Porter were killed when the aircraft crashed during practice for evacuations from coup-stricken Fiji.
Helicopter simulation expert Sylvain Manso talked the board through footage of two of the army's top pilots undertaking simulator runs recreating the ill-fated manoeuvre attempted by Capt Bingley.
Those that most closely followed Capt Bingley's route found it had resulted in "unrecoverable descent rate", Mr Manso told the board.
"There was insufficient available power to recover from the flight conditions from the defined ingress," Mr Manso said.
Video footage from a security camera aboard the Kanimbla allowed experts in photogrammetry, which is the science of measuring object position using images, to plot much of the Black Hawk's approach.
Another DSTO expert, Thuan Truong, brought to life an analysis of data from the FDR, retrieved from the helicopter wreckage.
Through a series of graphs depicting flight data recorded as frequently as eight times per second, Mr Truong was able to show how Capt Bingley desperately pulled hard on the control stick in a bid to raise the nose in the last two seconds before the crash.
The graphs also revealed how Capt Bingley frantically pumped the helicopter's right pedal as he tried to correct its course.
The FDR data also gave further weight to the role of "rotor droop", where the main rotor loses power, in causing the crash.
Although no data was recorded for the main rotor, Mr Truong said data showing how power to the tail rotor plummeted to 75 per cent could be applied with reasonable accuracy to the main rotor.
"There was a tremendous reduction of aircraft lift, at 75 per cent rpm (rotor speed) the aircraft lift is approximately half its weight," Mr Truong said.
Helicopter structure engineer Dominigo Lombardo said he had inspected the salvaged wreckage of the Black Hawk and found no evidence of engine failure.
"There was nothing that stood out as being unusual," he said.
The evidence from the FDR and simulator runs also ruled out engine failure.
The inquiry continues on Tuesday.

Dinosaurs coexisted with their ancestorsStory Highlights

Dinosaurs shared the Earth for millions of years with the species that were their ancestors, a new study concludes
Dinosaurs arose in the Late Triassic, between 235 million and 200 million years ago, and came to dominate the planet in the Jurassic, 200 million to 120 million years ago.
Scientists had thought the dinosaurs rapidly replaced their ancestor species. Indeed, until 2003, when a creature called Silesaurus was discovered in Poland, no dinosaur precursors had been found from the Late Triassic.
Now, researchers report in the journal Science they have evidence from northern New Mexico that dinosaurs and their precursor species coexisted for tens of millions of years.
Matthew T. Carrano, curator of dinosauria at the Smithsonian's National Museum of Natural History, said there has been a long-standing debate over whether dinosaurs replaced earlier species gradually or suddenly.
"What they have is a snapshot of the transition, and it's clear there is a persistent environment with dinosaurs and these other older animals. So, at least in this place in the southwestern U.S., it was not abrupt," said Carrano, who was not part of the research team.
"Finding dinosaur precursors ... together with dinosaurs tells us something about the pace of changeover. If there was any competition between the precursors and dinosaurs, then it was a very prolonged competition," Randall Irmis, a graduate student at the University of California, Berkeley and co-author of the report, said in a statement.
The team reported finding 1,300 fossil specimens, including several complete bones, at Hayden Quarry at Ghost Ranch, an area made famous through the paintings of Georgia O'Keeffe.
There were no complete skeletons, and researchers are continuing to work at the site.
Their finds included bones from both early dinosaurs and dinosaur precursors as well as remains of crocodile ancestors, fish and amphibians, all dating between 220 million and 210 million years ago.
Included were leg bones of the carnivorous Chindesaurus bryansmalli, a close relative of the Coelophysis, a well-known Triassic dinosaur. They said both walked on two legs, reminiscent of the much later Velociraptor depicted in the film "Jurassic Park."
They also found remains of a Dromomeron romeri, a relative of the 235 million-year-old Argentinian middle Triassic precursor called Lagerpeton. Dromomeron was between three and five feet long, the authors concluded.
Another discovery was an unnamed, four-footed beaked grazer about three times the size of Dromomeron, they said.

Highlights

Dinosaurs and their precursor species coexisted for tens of millions of years
Scientists had thought dinosaurs rapidly replaced their ancestor species
Dinosaurs arose between 235 million and 200 million years ago
They dominated the planet 200 million to 120 million years ago

The research was funded by>the National Geographic Society, the Theodore Roosevelt Memorial Fund and the Jurassic Foundation

Jurassic

From Wikipedia, the free encyclopedia

The Jurassic Period is a major unit of the geologic timescale that extends from about 199.6 ± 0.6 Ma (million years ago) to 145.4 ± 4.0 Ma, the end of the Triassic to the beginning of the Cretaceous. As with other geologic periods, the rock beds that define the start and end of the period are well identified but the exact dates are uncertain by 5 - 10 million years. The Jurassic constitutes the middle period of the Mesozoic era, also known as the "Age of Dinosaurs". The start of the period is marked by the major Triassic-Jurassic extinction event.
The Jurassic was named by Alexandre Brogniart for the extensive marine limestone exposures of the Jura Mountains, in the region where Germany, France and Switzerland meet.
Mesozoic era
Triassic
Jurassic
Cretaceous

Spitzer Finds Evidence for Planets with Four Parents.Planets with Four Parents? Spitzer Shows it's Possible,

Image credit: NASA/JPL-Caltech/UCLA

How many stars does it take to "raise" a planet? In our own solar system, it took only one -- our sun. However, new research from NASA's Spitzer Space Telescope shows that planets might be forming in systems with as many as four stars. This artist's concept illustrates one such quadruple-star system, called HD 98800. The system is still relatively young, at 10 million years old. One of its two pairs of stars is known to be circled by a dusty disk, which contains materials that are thought to clump together to form planets.

When Spitzer set its infrared gaze on the disk, it detected gaps. How did the gaps get there? One possible answer is that planets are growing in size and carving out lanes in the dust. Spitzer found two gaps in the disk. The inner gap is about as far away from its central stars as Mars and the asteroid belt are from our sun.

The outer gap is about as far away from its central stars as Jupiter is from the sun. HD 98800 is located 150 light-years away in the constellation TW Hydrae.

Before Spitzer set its gaze on HD 98800, astronomers had a rough idea of the system's structure from observations with ground-based telescopes. They knew the system contains four stars, and that the stars are paired off into doublets, or binaries. The stars in the binary pairs orbit around each other, and the two pairs also circle each other like choreographed ballerinas. One of the stellar pairs, called HD 98800B, has a disk of dust around it, while the other pair has none.

Although the four stars are gravitationally bound, the distance separating the two binary pairs is about 50 astronomical units (AU) -- slightly more than the average distance between our sun and Pluto. Until now, technological limitations have hindered astronomers' efforts to look at the dusty disk around HD 98800B more closely.

With Spitzer, scientists finally have a detailed view. Using the telescope's infrared spectrometer, Furlan's team sensed the presence of two belts in the disk made of large dust grains. One belt sits at approximately 5.9 AU away from the central binary, HD 98800B, or about the distance from the sun to Jupiter. This belt is likely made up of asteroids or comets. The other belt sits at 1.5 to 2 AU, comparable to the area where Mars and the asteroid belt sit, and probably consists of fine grains.

"Typically, when astronomers see gaps like this in a debris disk, they suspect that a planet has cleared the path. However, given the presence of the diskless pair of stars sitting 50 AU away, the inward-migrating dust particles are likely subject to complex, time-varying forces, so at this point the existence of a planet is just speculation," said Furlan.

Astronomers believe that planets form like snowballs over millions of years, as small dust grains clump together to form larger bodies. Some of these cosmic rocks then smash together to form rocky planets, like Earth, or the cores of gas-giant planets like Jupiter. Large rocks that don't form planets often become asteroids and comets. As these rocky structures violently collide, bits of dust are released into space. Scientists can see these dust grains with Spitzer's supersensitive infrared eyes.

According to Furlan, the dust generated from the collision of rocky objects in the outer belt should eventually migrate toward the inner disk. However, in the case of HD 98800B, the dust particles do not evenly fill out the inner disk as expected, due to either planets or the diskless binary pair sitting 50 AU away and gravitationally influencing the movement of dust particles.

"Since many young stars form in multiple systems, we have to realize that the evolution of disks around them and the possible formation of planetary systems can be way more complicated and perturbed than in a simple case like our solar system," Furlan added

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More Negativity Found in Space

Two teams of astronomers have identified the signal of a new negatively charged molecule, or anion, in space — only the third found in the cosmos. About 130 neutral and 12 positively charged molecules have been detected in space.
Along with its two siblings, the newfound anion, called octatetraynyl, could be among the building blocks of the organic molecules that make up living things. Even more interestingly, the two teams found the anion in entirely different cosmic locales.
Octatetraynyl is an odd little string of eight carbon atoms and a single hydrogen atom, written as C8H-. Its negative charge comes from the molecule having one electron more than is needed to balance the positive protons in all the atoms' nuclei.

It's not the sort of molecule that would last long on Earth, where there are all sorts of reactive molecules ready to make it neutral.
"Some of the things we're detecting in space you'd never find on Earth," said Anthony Remijan of the National Radio Astronomy Observatory (NRAO).
That's what makes them hard to find in space, he explained: Not having them here, we are hard put to know what they will look like. That has made the hunt a long and multi-disciplinary process.
The search began in the 1990s, when radio astronomers surveying the sky noticed some unusual lines showing up in spectrums of radio signal, Remijan explained.
Such lines are usually the calling cards of specific compounds, which absorb or emit very narrow radio bands. But in this case, no one knew of any compounds that produced such lines.
Other researchers, including Eric Herbst of Ohio State University, had already done some calculations and made models about what sorts of compounds might produce certain radio lines. But it took actual laboratory tests on manmade versions of the molecules to verify what kind of radio lines anions would make.
For octatetraynyl, that lab work was completed only last year.

Finally, radio astronomers went looking specifically for octatetraynyl's laboratory-tested lines. A Harvard team looked at a cold, dark gas cloud and a team from NRAO looked in the tenuous outer envelope of a dying star.
Both teams used the National Science Foundation's giant Green Bank Telescope (GBT) in West Virginia, which sees the universe in radio waves. Both found octatetraynyl.
"It's not so different physically," said Herbst of the two space environments. They have similar temperatures and densities, he said, though the way the anion was created could be different.

Which raises a big question: How do the molecules get their extra electron?
"One mechanism is a two-body process," said Herbst. In other words, a free-flying electron simply slams into a molecule and sticks.
As for whether more anions will be discovered in space, "There are many other candidates," Herbst told Discovery News. "But they have to be measured in the laboratory first." Then radio astronomers will know what to look for.

About Green Bank Telescope (GBT)

Construction has been completed on the world's largest fully steerable radio telescope at the National Radio Astronomy Observatory's site in Green Bank, Pocahontas County, West Virginia (79° 50' 23.40" W, 38° 25' 59.23" N : NAD83).
The GBT is described as a 100-meter telescope, but the actual dimensions of the surface are 100 by 110 meters. The overall structure of the GBT is a wheel-and-track design that allows the telescope to view the entire sky above 5 degrees elevation. The track, 64 m (210 ft) in diameter, is level to within a few thousandths of an inch in order to provide precise pointing of the structure while bearing 7300 metric tons (16,000,000 pounds) of moving weight.
The GBT is of an unusual design. Unlike conventional telescopes, which have a series of supports in the middle of the surface, the GBT's aperture is unblocked so that incoming radiation meets the surface directly. This increases the useful area of the telescope and eliminates reflection and diffraction that ordinarily complicate a telescope's pattern of response. To accommodate this, an off-axis feed arm cradles the dish, projecting upward at one edge, and the telescope surface is asymmetrical. It is actually a 100-by-110 meter section of a conventional, rotationally symmetric 208-meter figure, beginning four meters outward from the vertex of the hypothetical parent structure.
The GBT's lack of circular symmetry greatly increases the complexity of its design and construction. The GBT is also unusual in that the 2,004 panels that make up its surface are mounted at their corners on actuators, little motor-driven pistons, which make it easier to adjust the surface shape. Such adjustment is crucial to the high-frequency performance of the GBT in which an accurate surface figure must be maintained.
The GBT is equipped with a novel laser-ranging system. Beams of light are reflected within the structure and between the telescope and a series of ground stations surrounding the telescope in a broad ring. Monitoring of these beams show the deformation of the figure under such stresses as gravity, wind and temperature differences, and allow the telescope's motors, subreflector and surface panel actuators to compensate for any ill effects.