Posted on by Fraser Cain

Cleaning Up Kennedy Space Center After Frances

For one of the world’s biggest buildings, before and after images captured the force of the storm. With its footprint the size of Texas, hurricane Frances had pounded Cape Canaveral over the weekend and left a natural scar on one of the world’s manmade wonders.

Originally built for assembly of Apollo/Saturn vehicles and later modified to support Space Shuttle operations, the Vehicle Assembly Building (VAB) is often referred to as the only enclosed space big enough for interior clouds to form. But when a hurricane looms off the Florida coast and dark clouds gather to drench the beaches, the novelty of forming interior clouds loses some of its charm.

It is not the tallest, just one of the more spacious. Its high-bay area is 525 feet tall (more than 45 stories high), while its low-bay area is 210 feet tall. The VAB occupies 8 acres of land, making it the largest in volume (129 million cubic feet). The volume is like half the height of the tallest skyscraper, but then with that same tower turned on three axes, with nearly equal height, width and depth. When open, the T-shaped door alone is more than 40 stories tall.

When constructed in the 1960’s to stack the Saturn rockets–each about the size of an aircraft carrier if stood up vertically–the VAB came to symbolize big-scale thinking. In addition to sheltering the Apollo rockets, it could accomodate rollbacks of a shuttle during the predictable fall hurricane season. In total, six skyscrapers could fit inside what is the landmark against an otherwise flat Florida marsh lacking an urban skyline. But from its outset, if NASA needed a building to shelter a moon rocket, then a group of construction engineers would conceive hoisting the biggest one of its kind.

Max Urbahn, who headed the design team of architects and engineers for the Vehicle Assembly Building stated the design challenge well when he said: “The VAB is not so much a building to house a moon vehicle as a machine to build a moon craft. The Launch Control Center that monitors and tests every component that goes into an Apollo vehicle is not so much a building as an almost-living brain.”

When General Thomas Stafford testified to the Presidential blue-ribbon commission on “Moon to Mars and Beyond”, he cited specifically how remarkable the early sixties were for construction on the Florida coast. “In the early 1960’s the Cape was strictly palmettos, rattlesnakes, and palm trees. In 6 years, that was built to the Vehicle Assembly Building (VAB), and we launched the first Saturn flag. And most of it was done with a slide rule.”

As the VAB tried to weather 100 mile-per-hour gales, the adage that ‘build it and they will come’ took on special significance: those who had to evacuate included nearly the entire 14,000 person Kennedy Space Center (KSC). According to its design specifications, the VAB doors can withstand winds of 125 miles per hour and can be opened and closed in a 63 mile-per-hour wind. The building lived up to its design, but its integrity was questionable earlier in the week when Frances looked like it might make landfall with 140 mph force winds.

As NASA Administrator, Sean O’Keefe described in a statement: “Kennedy Space Center suffered significant damage as Hurricane Frances swept across Florida.” After the weekend, early assessment of this landmark facility showed about 820 panels were torn off the VAB during the storm. Initial review of the interior, however, indicated no serious damage to equipment, including two Space Shuttle External Tanks.

Preliminary inspections of the center’s two launch pads indicate they appear in good shape. The SWIFT spacecraft for studying Gamma Ray Bursts, which is scheduled for launch early next month, also appears fine, but the building where it rode out the storm did sustain damage. Also, power was restored today to the third and final Orbital Processing Facility, which houses the Space Shuttle Discovery.

In addition to housing the shuttle rocket stacks, many astrobiology missions have historical ties to critical assets at the Cape. From the Hubble telescope launch to various human missions on space station, the shuttle stack has been mounted in the VAB. In fact the skyline at Cape Canaveral gives a running account of important astrobiology objectives. During a controlled explosion in October 2000, the historical launch pad 41 dating back to 1965 gave way to a new Atlas V tower. That part of the now modified Florida skyline had witnessed the launch of two Viking missions to Mars and Voyager’s planetary probe, both of which had led the way for modern astrobiology missions to the inner and outer solar system.

O’Keefe spoke to the NASA tradition of recovery, when he concluded that “We have a documented history of overcoming adversity and pulling together.” NASA has not assessed yet whether the storm damage will affect the planned spring reflight of the shuttle as it returns to orbit since the Columbia tragedy.

Original Source: NASA Astrobiology Article

Posted on by Fraser Cain

Dark Matter is Tugging at a Galactic Cluster

A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA’s Chandra X-ray Observatory. Astronomers think that most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect.

A Chandra survey of the Fornax galaxy cluster revealed a vast, swept-back cloud of hot gas near the center of the cluster. This geometry indicates that the hot gas cloud, which is several hundred thousand light years in length, is moving rapidly through a larger, less dense cloud of gas. The motion of the core gas cloud, together with optical observations of a group of galaxies racing inward on a collision course with it, suggests that an unseen, large structure is collapsing and drawing everything toward a common center of gravity.

“At a relatively nearby distance of about 60 million light years, the Fornax cluster represents a crucial laboratory for studying the interplay of galaxies, hot gas and dark matter as the cluster evolves.” said Caleb Scharf of Columbia University in New York, NY, lead author of a paper describing the Chandra survey that was presented at an American Astronomical Society meeting in New Orleans, LA. “What we are seeing could be associated directly with the intergalactic gas surrounding a very large scale structure that stretches over millions of light years.”

The infalling galaxy group, whose motion was detected by Michael Drinkwater of the University of Melbourne in Australia, and colleagues, is about 3 million light years from the cluster core, so a collision with the core will not occur for a few billion years. Insight as to how this collision will look is provided by the elliptical galaxy NGC 1404 that is plunging into the core of the cluster for the first time. As discussed by Scharf and another group led by Marie Machacek of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., the hot gas cloud surrounding this galaxy has a sharp leading edge and a trailing tail of gas being stripped from the galaxy.

“One thing that makes what we see in Fornax rather compelling is that it looks a lot like some of the latest computer simulations,” added Scharf. “The Fornax picture, with infalling galaxies, and the swept back geometry of the cluster gas – seen only with the Chandra resolution and the proximity of Fornax – is one of the best matches to date with these high-resolution simulations.”

Over the course of hundreds of millions of years, NGC 1404’s orbit will take it through the cluster core several times, most of the gas it contains will be stripped away, and the formation of new stars will cease. In contrast, galaxies that remain outside the core will retain their gas, and new stars can continue to form. Indeed, Scharf and colleagues found that galaxies located in regions outside the core were more likely to show X-ray activity which could be associated with active star formation.

The wide-field and deep X-ray view around Fornax was obtained through ten Chandra pointings, each lasting about 14 hours. Other members of the research team were David Zurek of the American Museum of Natural History, New York, NY, and Martin Bureau, a Hubble Fellow currently at Columbia.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA’s Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images are available at:

http://chandra.harvard.edu
and
http://chandra.nasa.gov

Original Source: Chandra News Release

Posted on by Fraser Cain

Colliding Galaxies Awash With Star Formation

NASA’s Spitzer Space Telescope has set its infrared sight on a major galactic collision and witnessed not death, but a teeming nest of life.

The colliding galaxies, called the Antennae galaxies, are in the process of merging together. As they churn into each other, they throw off massive streamers of stars and dark clouds of dust. Spitzer’s heat-seeking eyes peered through that dust and found a hidden population of newborn stars.

The new Spitzer image, available at http://www.spitzer.caltech.edu/Media/releases/ssc2004-14/visuals.shtml, is reported in one of 86 Spitzer papers published in the September issue of The Astrophysical Journal Supplement. This special all-Spitzer issue comes just after the one-year anniversary of the observatory’s launch, and testifies to its tremendously successful first year in space.

“This abundance of Spitzer papers just one year after launch shows that the telescope is truly providing a new window on the universe,” said Dr. Michael Werner, project scientist for Spitzer at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “These papers report the earliest results, so the best is yet to come.”

In the latest Antennae galaxies study, Spitzer uncovered a new generation of stars at the site where the two galaxies clash.

“We theorized that there were stars forming at that site, but we weren’t sure to what degree,” said Dr. Zhong Wang, lead author of the new paper and an astronomer at the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. “Now we see that the majority of star-forming activity in both galaxies occurs in the overlap regions where the two meet.”

The Antennae galaxies are a classic example of a galactic merger in action. These two spiral galaxies, located 68 million light-years away from Earth, began falling into each other around a common center of gravity about 800 million years ago. As they continue to crash together, clouds of gas are shocked and compressed in a process thought to trigger the birth of new stars. Astronomers believe that the two galaxies will ultimately merge into one spheroidal-shaped galaxy, leaving only hints of their varied pasts.

Galactic mergers are common throughout the universe and play a key role in determining how galaxies grow and evolve. Our own Milky Way galaxy, for example, will eventually collide with our closest neighbor, the Andromeda galaxy.

Previous images of the Antennae taken by visible-light telescopes show striking views of the swirling duo, with bright pockets of young stars dotting the spiral arms. At the center of the galaxies, however, where the two overlap, only a dark cloud of dust can be seen. In the new false-color Spitzer image, which has been combined with an image from a ground-based, visible-light telescope to highlight new features, this cloud of buried stars appears bright red. The visible-light information, on the other hand, is colored blue and indicates regions containing older stars. The nuclei, or centers, of the two galaxies are white.

“This more complete picture of star-formation in the Antennae will help us better understand the evolution of colliding galaxies, and the eventual fate of our own,” said Dr. Giovanni Fazio, a co-author of the research and an astronomer at the Harvard-Smithsonian Center for Astrophysics.” Fazio is principal investigator for the infrared array camera on Spitzer, which captured the new Antennae image.

JPL manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. JPL is a division of Caltech. Spitzer’s infrared array camera was built by NASA Goddard Space Flight Center, Greenbelt, Md.

Information about Spitzer can be found at http://www.spitzer.caltech.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Gemini Sees Galaxies in a Royal Rumble

A stunning image released today by the Gemini Observatory captures the graceful interactions of a galactic ballet, on a stage some 300 million light years away, that might better be described as a contortionist’s dance.

The galaxies, members of a famous troupe called Stephan’s Quintet, are literally tearing each other apart. Their shapes are warped by gravitational interactions occurring over millions of years. Sweeping arches of gas and dust trace the interactions and possible ghost-like passage of the galaxies through one another. The ongoing dance deformed their structures while spawning a prolific fireworks display of star formation fueled by clouds of hydrogen gas that were shocked into clumps to form stellar nurseries.

This unprecedented image of the cluster provides a unique combination of sensitivity, high resolution and field of view. “It doesn’t take long to reach an incredible depth when you have an 8-meter mirror collecting light under excellent conditions,” said Travis Rector of the University of Alaska, Anchorage who helped obtain the data with the Gemini North Telescope on Mauna Kea. “We were able to capture these galaxies at many different wavelengths or colors. This allowed us to bring out some remarkable details in the final color image that have never been seen before in one view.”

One striking element of the image is a collection of vibrant red clumps that mark star-forming regions within a galaxy called NGC 7320. Although its relation to the other galaxies in the cluster has been the subject of some controversy, most astronomers now think that the galaxy leads a relatively tranquil existence in the foreground, safely isolated from the violent quarrels of the more distant cluster.

Spectroscopic data show that NGC 7320 has an apparent velocity away from us of about 800 kilometers per second. In contrast, the rest of the group is being carried away from us by the expansion of the universe at over 6,000 kilometers per second. Using current models for the expanding universe, this would put the bulk of the cluster almost 8 times farther away from us than NGC 7320.

The vivid red patches scattered across the spiral arms of NGC 7320 in the new Gemini image provide a dramatic illustration of how these differing apparent velocities can impact our view. NGC 7320 and the other cluster galaxies have regions of intense star formation indicated by glowing clouds of hydrogen gas called HII regions. These areas appear distinctly red because a selective filter was used which only passes a special color of red light, called hydrogen alpha, that is produced in the HII regions. In the higher-velocity members of the cluster, prominent HII clumps dominate around the two closely interacting central galaxies but they do not appear red in the image. In these galaxies, the HII glow was Doppler-shifted beyond the range of the selective filter, and was therefore not detected.

The interacting members of Stephan’s Quintet appear destined to continue their dance for millions more years. Eventually, this dance will probably cause some of the galaxies in the cluster to completely lose their current identity, combining into even fewer objects than we see today.

Stephan’s Quintet was discovered in 1877 by the French astronomer Edouard Stephan using the Foucault 80-centimeter reflector at the Marseilles Observatory. The cluster is listed in the Hickson Compact Group Catalog as number 92. It has been studied extensively at all wavelengths including imaging by the Hubble Space Telescope. Recent observations of star cluster formation near Stephan’s Quintet with Gemini can be found here.

Original Source: Gemini News Release

Posted on by Fraser Cain

NASA Assesses the Damage From Frances

NASA teams are surveying the Kennedy Space Center (KSC) for damage caused by Hurricane Frances. Initial assessments show KSC weathered the storm fairly well. There are no reports of any injured KSC workers, and there does not appear to be damage to the Space Shuttles Discovery, Atlantis, and Endeavour.

“Our initial feeling is we dodged a real bullet,” said Kennedy Space Center Director Jim Kennedy. “Even though this was the worst storm ever to hit KSC, I feel very fortunate.”

KSC will remain closed Tuesday for most employees. Workers who need to report to work will be notified. A more detailed damage assessment is expected Tuesday.

The most serious damage reported so far is to the center’s landmark structure, the Vehicle Assembly Building (VAB), and to the facility that manufactures Space Shuttle Thermal Protection System tiles and blankets.

Sustained wind of more than 70 mph was recorded during the storm. Approximately 1,000 panels were blown off the VAB. In some places, exterior panels and underlying sub-panels are missing, leaving the interior of the building exposed to the elements. There are several holes, including one estimated to be 50 feet by 50 feet, in the building. Emergency operations personnel have not entered the VAB, as several loose panels are still hanging from the building and present a safety hazard.

The KSC Space Shuttle tile and blanket facility’s roof is partially torn off, and there is significant wall damage. Damage to the facility and its effect on the Space Shuttle Return to Flight effort is not yet known. The building housing International Space Station hardware and modules appears to be in good shape. KSC was powered down last week as Frances approached. Emergency operations teams are working to restore electricity and phone service to the center. NASA will provide new information as available.

Original Source: NASA News Release

Posted on by Fraser Cain

Final Helios Report Released

The board that investigated the loss of the remotely operated Helios Prototype aircraft during a test flight last summer released its final report today.

The board determined that the mishap resulted from the inability to predict, using available analysis methods, the aircraft?s increased sensitivity to atmospheric disturbances such as turbulence, following vehicle configuration changes required for the long-duration flight demonstration.

The Helios Prototype aircraft involved in the mishap was a proof-of-concept solar electric- powered flying wing designed to operate at high altitudes for long duration flight. The failure occurred during a flight from the U.S. Navy?s Pacific Missile Range Facility (PMRF) on the Hawaiian island of Kauai on June 26, 2003.

The propeller-driven aircraft had been flying under guidance of ground-based controllers from AeroVironment, Inc., of Monrovia, Calif., the plane?s builder and operator, with assistance from NASA Dryden Flight Research Center personnel. The aircraft was destroyed when it sustained structural failure and fell into the Pacific Ocean. No other property damage or any injuries occurred as a result of the mishap.

The lightweight, highly flexible flying wing took off at 10:06 a.m. local time. At 10:22 and 10:24 a.m., the aircraft encountered atmospheric turbulence, typical of conditions expected by the test crew, causing abnormally high wing dihedral (upward bowing of both wingtips). Unobserved mild pitch oscillations began, but quickly diminished, according to post-test data analysis.

At about 10:36 a.m., the aircraft again experienced normal turbulence and transitioned into an unexpected, persistent high wing dihedral configuration. As a result, the aircraft became unstable, exhibiting growing pitch oscillations. Airspeed deviated from the normal flight speed, with the deviations rapidly increasing with every cycle of the oscillation. The aircraft?s design speed was subsequently exceeded. The resulting high dynamic pressures caused the wing leading edge secondary structure on the outer wing panels to fail and the solar cells and skin on the upper surface to rip off. The remotely piloted aircraft came down within the confines of the Pacific Ocean test range, northwest of PMRF.

?The mishap underscores our need to assess carefully our assumptions as we push the boundaries of our knowledge,? said Dr. Victor Lebacqz, Associate Administrator for NASA?s Office of Aeronautics. ?It should not, however, diminish the significant progress AeroVironment and NASA have made over the past 10 years in advancing the capabilities of this unique class of aircraft on many successful flights, including Helios’ record setting flight to just under 97,000 feet altitude in August 2001. It is important that we learn from this experience, and apply the board’s findings and recommendations to help ensure the payoffs of such vehicles are fully realized.?

The report is available on the Web at: http://www.nasa.gov/pdf/64317main_helios.pdf

Original Source: NASA News Release

Posted on by Fraser Cain

Astronauts Complete Final Spacewalk

Smoothly and ahead of schedule, Expedition 9 Commander Gennady Padalka and NASA Science Officer Mike Fincke completed the fourth and final spacewalk of their six-month mission today. Padalka and Fincke spent five hours, 21 minutes outside completing mainenance tasks and installing antennas to prepare for the initial arrival of a new European cargo ship next year.

Wearing Russian Orlan spacesuits, Padalka and Fincke began the spacewalk at 11:43 a.m. CDT, emerging from the Pirs airlock affixed to the Zvezda Service Module. It was Padalka?s sixth career spacewalk and the fourth for Fincke, all of his conducted during this expedition. The spacewalk was supervised by Russian flight controllers at the Mission Control Center in Korolev, outside Moscow.

After setting up tools and tethers, Padalka and Fincke quickly went to work. On the Zarya module, they replaced a pump control panel that measures the module’s coolant levels. They then installed a series of tether guides on four handrails. The guides are intended to prevent future spacewalkers? tethers from becoming snagged.

As the Station moved into orbital darkness, the spacewalkers took a rest break. During the break, flight controllers in Houston collected data on the orientation of the outpost. The information will help determine if the cooling systems of the Russian spacesuits contribute to changes in the Station?s orientation. Throughout today’s spacewalk, the Station remained in predicted orientations. No unanticipated measures were needed to maintain its stability.

Padalka and Fincke spent two and a half hours on the exterior of Zvezda, installing three communications antennas at its aft end. Those antennas, along with other equipment installed during an Aug. 3 spacewalk, will be used next year. They will guide the European Space Agency?s unpiloted Automated Transfer Vehicle (ATV), the “Jules Verne” cargo ship, to its maiden docking with the Station. Three more ATV navigation antennas will be installed by the next Station crew, Expedition 10, in February. The Expedition 11 crew will install ATV communications gear inside Zvezda as well.

Padalka and Fincke returned to Pirs and installed protective handrail covers at one of the two airlock hatches. The covers will ensure tethers do not inadvertently wrap around the handrails.

Fincke also photographed a suitcase-sized tray of Japanese commercial experiments mounted on Zvezda to measure the effect of micrometeoroids on a variety of materials. Called Micro-Particle Capturer and Space Environment Exposure Devices, they were installed on Zvezda almost three years ago.

With their work done, Padalka and Fincke returned to the airlock and closed the hatch at 5:04 p.m. CDT. The spacewalk was the 56th in support of Station assembly and maintenance and the 31st based from the Station. In all, Padalka and Fincke have spent 15 hours and 45 minutes outside the Station during their four spacewalks together. To date, spacewalkers have spent more than 338 hours outside the Station for maintenance and assembly work.

For information on the crew’s activities aboard the Space Station, future launch dates, as well as a list of opportunities to see the Station from anywhere on the Earth, visit:

http://spaceflight.nasa.gov/

For details on Station science operations provided by the Payload Operations Center at NASA’s Marshall Space Flight Center in Huntsville, Ala., visit:

http://scipoc.msfc.nasa.gov/

Original Source: NASA News Release

Posted on by Fraser Cain

Hubble Sees the Stingray Nebula

This is the Stingray Nebula (Henize 1357), the youngest known planetary nebula, as seen by the NASA/ESA Hubble Space Telescope. Twenty five years ago, the nebulous gas entombing the dying star at the centre was not hot enough to glow.

This image shows a rare moment in the final stages of a star’s life: a shell of gas cast off by a dying star which then begins to glow like a neon light bulb. Images of planetary nebulae in their formative years like this can yield new insights into the last moments of ordinary stars like our Sun.

A planetary nebulae forms after an aging, low-mass star swells to become a ‘red giant’ and blows off some of its outer layers of material. As the nebula expands away from the star, the star’s remaining core gets hotter and heats the gas until it glows. A fast wind – material propelled outward from the hot central star ? compresses the gas and pushes the gas bubble outward.

The Stingray Nebula is an ‘infant’ in relative terms, because only within the past 25 years did its central star rapidly heat up enough to make the nebula glow. While stars typically exist for millions of years, the transition to a visible planetary nebula takes only about 100 years ? the blink of an eye compared to a star’s lifetime – which is why no younger planetary nebulae have ever been identified.

Named because its shape resembles a stingray fish, the nebula is one-tenth the size of most planetary nebulae and is 18 000 light-years away in the direction of the southern constellation Ara (the Altar). Because of its small size, no details of the Stingray Nebula were visible before Hubble observations were first carried out in 1993. Those images were the first to show the structure of the nebula. This image was taken in 1997.

Original Source: ESA News Release

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Saturn’s Cool… Well, Its Rings Are

The Cassini spacecraft has taken the most detailed temperature measurements to date of Saturn’s rings. Data taken by the composite infrared spectrometer instrument on the spacecraft while entering Saturn’s orbit show the cool and relatively warm regions of the rings.

This false-color image shows that the temperatures on the unlit side of Saturn’s rings vary from a relatively warm 110 Kelvin (-261 degrees Fahrenheit, shown in red), to a cool 70 Kelvin (-333 degrees Fahrenheit, shown in blue). The green represents a temperature of 90 Kelvin (-298 degrees Fahrenheit). Water freezes at 273 Kelvin (32 degrees Fahrenheit).

The data show that the opaque region of the rings, like the outer A ring (on the far right) and the middle B ring, are cooler, while more transparent sections, like the Cassini Division (in red just inside the A ring) or the inner C ring (shown in yellow and red), are warmer. Scientists had predicted this might be the case, because the opaque ring areas would let less light through, and the transparent areas, more. These results also show, for the first time, that individual ringlets in the C ring and the Cassini Division are cooler than the surrounding, more transparent regions.

The temperature data were taken on July 1, 2004, shortly after Saturn orbit insertion. Cassini is so close to the planet that no pictures of the unlit side of the rings are available, hence the temperature data was mapped onto a picture of the lit side of the rings. Saturn is overexposed and pure white in this picture. Saturn?s moon Enceladus is visible below the rings, toward the center.

The composite infrared spectrometer, one of 12 instruments on Cassini, will measure infrared emissions from atmospheres, rings and surfaces. This spectrometer will create vertical profiles of temperature and gas composition for the atmospheres of Titan and Saturn. During Cassini?s four-year tour, the instrument will also gather information on the thermal properties and composition of Saturn?s rings and icy moons.

Cassini-Huygens is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science and Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA’s Goddard Space Flight Center, Greenbelt, Md.

For this image and for the latest news about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini. For in-depth mission information, visit http://saturn.jpl.nasa.gov. For more information on the Composite Infrared Spectrometer, visit http://cirs.gsfc.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Getting Gravity Probe B Ready Was Tough

It’s “all systems go” for one of the most ambitious physics experiments ever attempted.

On August 27th, after four months in orbit, NASA’s Gravity Probe B satellite began its year-long hunt for signs of a subtle space-time vortex around Earth predicted by Einstein’s theory of relativity. The search isn’t going to be easy, but for scientists involved, one of the hardest parts is already over: months of delicately starting up and checking out the satellite, when one wrong move could have ruined the experiment before it ever got started.

“It’s a long and tortuous story,” says Francis Everitt, principal investigator for Gravity Probe B (GP-B) and a professor at Stanford University.

One of the key parts of GP-B is an onboard telescope that locks on to the star IM Pegasus, which serves as a fixed point of reference in the sky. Everitt and his colleagues had figured that pointing the telescope at that star would be quick and painless, taking only three days after the launch.

Instead it took weeks.

First, sunlight reflecting off floating dust particles confused the satellite’s star-tracking sensors. These sensors use the locations of constellations to orient the spacecraft, and the tiny shining specs looked like stars. The dust eventually cleared, but then another problem arose: Cosmic radiation in the form of high-speed protons peppered the telescope’s light sensor, causing false signals. Mission scientists had to tweak the satellite’s software to ignore these pulses. And on it went like this for weeks; scientists would solve one problem only to encounter another.

“Now it has become very routine, and we only take about a minute to acquire the star as we come up over the horizon,” Everitt says. (The satellite loses sight of the guide star during each orbit because it passes behind the Earth, so it must reacquire the star as it comes back into sight.)

The purpose of the telescope and the guide star is to help scientists keep track of four spinning spheres, or gyros, onboard the satellite. These gyros, which will be listed in a forthcoming edition of the Guinness Book of World Records as the roundest objects ever manufactured, are the heart of the experiment. In the beginning, their spin axes are aligned with IM Pegasus. If space-time around Earth is really twisted, as Einstein says, the gyros will wobble, slowly drifting out of alignment with the distant star during GP-B’s one-year mission.

“One of the things all of us were terribly worried about was getting some dirt in the gyro housings,” Everitt says. The gyros float a near-perfect vacuum, and only a thousandth-of-an-inch gap separates the spheres from their casings.

“The gyros were cleaned before they went up, but we gave this thing a tremendous vibration during launch. Wouldn’t you expect a piece of dirt to come in through one of the pump-out ports, land right on one of the gyros and jam it?” he says. “That would be the end of that gyro.”

This time all the worrying was for nothing. “The gyros have all been as clean as a whistle,” he says. They’re suspended in their casings, aligned with the guide star, and spinning thousands of times per minute. “Amazing, delightful.”

Now the gathering of science data begins. The satellite’s onboard computers should be able to handle this phase of the mission automatically. Still, at least one person will be on duty monitoring GP-B at all times throughout the year, Everitt says. “It should run itself, but you can never relax.”

After more than 40 years of methodical planning and four months of intense troubleshooting, GP-B’s scientists feel “a real sense of gladness,” he says. “What a difference it makes to be up there and operating. How thrilling that is. We all feel that.”

“Some people,” laughs Everitt, “are talking about taking a week or two of well-deserved vacation.”

Original Source: NASA Science News