Gravity Map Released

Image credit: NASA

The Gravity Recovery and Climate Experiment (Grace) mission has created the most accurate map of the Earth’s gravity field. The joint NASA-German Aerospace Center mission consists of two spacecraft connected by a cable which is able to measure fluctuations in the Earth’s gravity to a precision of a few centimetres. They found that the gravity field can fluctuate by as much as 200 metres around the world. This gravity map will give future water level measurements better accuracy, and help scientists better understand the slow redistribution of mass on the planet.

The joint NASA-German Aerospace Center Gravity Recovery and Climate Experiment (Grace) mission has released its first science product, the most accurate map yet of Earth’s gravity field. Grace is the newest tool for scientists working to unlock secrets of ocean circulation and its effects on climate.

Created from 111 days of selected Grace data, to help calibrate and validate the mission’s instruments, this preliminary model improves knowledge of the gravity field so much it is being released to oceanographers now, months in advance of the scheduled start of routine Grace science operations. The data are expected to significantly improve our ability to understand ocean circulation, which strongly influences weather and climate.

Dr. Byron Tapley, Grace principal investigator at UT’s Center for Space Research, called the new model a feast for oceanographers. “This initial model represents a major advancement in our knowledge of Earth’s gravity field. “Pre- Grace models contained such large errors many important features were obscured. Grace brings the true state of the oceans into much sharper focus, so we can better see ocean phenomena that have a strong impact on atmospheric weather patterns, fisheries and global climate change.”

Grace is accomplishing that goal by providing a more precise definition of Earth’s geoid, an imaginary surface defined only by Earth’s gravity field, upon which Earth’s ocean surfaces would lie if not disturbed by other forces such as ocean currents, winds and tides. The geoid height varies around the world by up to 200 meters (650 feet).

“I like to think of the geoid as science’s equivalent of a carpenter’s level, it tells us where horizontal is,” Tapley said. “Grace will tell us the geoid with centimeter-level precision.”

So why is knowing the geoid height so important? JPL’s Dr. Lee-Lueng Fu, scientist on Topex/Poseidon and Jason project said, “The ocean’s surface, while appearing flat, is actually covered with hills and valleys caused by currents, winds and tides, and also by variations in Earth’s gravity field. “Scientists want to separate out these gravitational effects, so they can improve the accuracy of satellite altimeters like Jason and Topex/Poseidon, which measure sea surface height, ocean heat storage and global ocean circulation. This will give us a better understanding of ocean circulation and how it affects climate.”

Dr. Michael Watkins, Grace project scientist at JPL, put improvements to Earth’s gravity model into perspective. “Scientists have studied Earth’s gravity for more than 30 years, using both satellite and ground measurements that were of uneven quality. “Using just a few months of our globally uniform quality Grace data, we’ve already improved the accuracy of Earth’s gravity model by a factor of between 10 and nearly 100, depending on the size of the gravity feature. In some locations, errors in geoid height based upon previous data were as much as 1 meter (3.3 feet). Now, we can reduce these errors to a centimeter (0.4 inches) in some instances. That’s progress.”

Dr. Christoph Reigber, Grace co-principal investigator at GeoForschungsZentrum Potsdam, said, “As we continue to assess and refine Grace’s instruments and subsystems, we’re confident future monthly gravity solutions will be even better than the map we’re releasing now. “Those solutions will allow us to investigate processes associated with slow redistribution of mass inside Earth and on its land, ocean and ice surfaces. Our initial attempts to identify such small gravity signals with Grace look very promising.”

Grace senses minute variations in gravitational pull from local changes in Earth’s mass by precisely measuring, to a tenth of the width of a human hair, changes in the separation of two identical spacecraft following the same orbit approximately 220 kilometers (137 miles) apart. Grace will map the variations from month to month, following changes imposed by the seasons, weather patterns and short-term climate change.

Original Source: University of Texas News Release

Air Force Suspends Business With Boeing

Image credit: Boeing

The US Air Force announced its investigation findings today, that The Boeing Company had committed serious violation of federal law by using propriety documents from Lockheed Martin to win a series of launches during a 1998 contract competition. The Air Force said that Boeing will forfeit seven of its 19 launch contracts and several upcoming launch contracts will be awarded to Lockheed Martin instead of Boeing. All told, Boeing will lose $1 billion of Air Force launch business.

The Air Force announced today that it has determined that The Boeing Company has committed serious violations of federal law based on its review into allegations of wrongdoing by Boeing during the 1998 Evolved Expendable Launch Vehicle (EELV) source selection. As a result, the Air Force will suspend three Boeing Integrated Defense System business units and three former Boeing employees from eligibility for new government contracts. The suspensions are issued against The Boeing Company’s Launch Systems, Boeing Launch Services and Delta Program business units as they existed in the Boeing organizational structure as of July 21, 2003. This suspension will apply to these business units regardless of where they fall in any Boeing reorganization.

The individuals suspended are William David Erskine, former ground operations lead on Boeing’s EELV program; Kenneth V. Branch, former senior engineer/scientist on Boeing’s EELV program; and Larry Dean Satchell, a former member of Boeing’s EELV proposal team.

In addition, the Air Force will notify Boeing of its intent to reallocate launches under its existing EELV contract, which was awarded in October 1998 and is known as Buy I. Under this reallocation the Air Force will reduce the total number of Boeing Buy I Delta IV launches from 19 to 12. The Air Force will increase the total number of Lockheed Martin Buy I Atlas V launches from 7 to 14.

Further, the Air Force will permit Lockheed Martin to develop a west coast launch capability at Vandenberg AFB by upgrading an existing launch facility.

The Air Force also announced the results of its EELV Buy II decision. The Air Force disqualified Boeing from the award of three Buy II launches and plans to award Lockheed Martin three Buy II launches from Vandenberg AFB.

“Our inquiry into Boeing found that they were in possession of thousands of pages of Lockheed Martin proprietary EELV documents during the 1998 source selection,” said Under Secretary of the Air Force Peter B. Teets. “As a matter of policy we do not tolerate breaches of procurement integrity and we hold industry accountable for the actions of their employees. We believe the suspension is necessary and we hope all contractors will take note and strive to enforce the highest integrity standards in their organizations.”

The Boeing Delta IV and Lockheed Martin’s Atlas V are the two families of EELVs developed with the Air Force to modernize and reduce the cost of the nation’s spacelift operation while providing the United States with assured access to space.

Original Source: Air Force News Release

Unlocking the Secrets of Dwarf Galaxies

Image credit: UCSC

A team of astronomers from the University of Cambridge have been researching a rare group of galaxies, known as dwarf spheroidal galaxies, which seem to have few stars but massive amounts of “dark matter”. The team analyzed one such galaxy and found that the stars in the outer edges were moving so quickly that the galaxy could only stay together if it had 100 times more dark matter than the mass of the stars alone. This research will help astronomers understand how galaxies are formed and how dark matter plays into their composition.

New research on dwarf spheroidal galaxies by a team of astronomers at the University of Cambridge promises a real astronomical first: detection, for the first time, of the true outer limits of a galaxy.

The team is presenting today (23 July 2003) at the 25th General Assembly of the International Astronomical Union (IAUXXV) in Sydney, Australia. The research could provide the key to understanding how larger galaxies were formed, including our own Milky Way galaxy.

The rare dwarf spheroidal galaxies display few stars but contain massive amounts of ‘dark matter’ or matter that does not emit radiation that can be observed by astronomers. The team studied these galaxies in detail using some of the largest optical telescopes on earth in order to probe their dark secrets. Dwarf spheroidal galaxies are widely believed to be the building blocks from which galaxies were formed.

By studying the motion of many stars the scientists have created a picture of how the mass of the galaxy is arranged. Surprisingly, when the Cambridge team looked at the stars at the edge of one such galaxy, Draco, they found that the outer stars were moving so quickly that the galaxy could only stay together if it contained 100 times more dark matter than the mass of the stars alone. Using detailed models of the motions of stars in a galaxy containing large quantities of dark matter, the group was able to demonstrate their observations could only be understood if the galaxy was surrounded by a large halo of dark matter.

Observations of the Ursa Minor dwarf spheroidal galaxy presented a new complication in the study. The team found an unexpected clump of slow-moving stars interpreted as the dead remains of one of the pure star systems, a globular cluster. The cluster should have been scattered across the galaxy, but it was still held together. The team realised this was only possible if the dark matter were arranged in a manner very differently from standard galaxies.

In May 2003, further research into Ursa Minor showed the stars in the very outermost parts are not moving quickly like the stars at the edge of Draco. Several theories are being investigated including dark matter from edge of Ursa Minor has been snatched away from the galaxy by its massive parent, the Milky Way, allowing some stars to wander gently away from their parent. Or they could be stars which wandered too close to other stars in the centre of the galaxy and were slung out to the edge of the galaxy as a result.

Whatever the explanation, the findings promise a real astronomical first: detection, for the first time, of the true outer limits of a galaxy.

Gerry Gilmore, Professor of Experimental Philosophy at the Institute of Astronomy at the University of Cambridge, said:

“This research, utilising some of the largest optical telescopes on earth, has provided us with insight to the makeup of these rare dwarf galaxies. This research helps astronomers better understand how galaxies were formed, and help take into account dark matter in all galaxies.”

Original Source: Cambridge University News Release

Board Reveals Why the X-43A Failed

Image credit: NASA

A NASA investigation board released its findings on Wednesday that revealed why the X-34A Hyper-X prototype failed during a test on June 2, 2001. The investigators found that various miscalculations built into the prototype collectively caused the mishap. The X-34A is an experimental program to develop an air breathing hypersonic aircraft that could eventually fly up to 10 times the speed of sound. The X-34A was attached to the front of a Pegasus rocket and launched from a modified B-52 bomber. Only 13 seconds into its flight the aircraft went out of control, and was destroyed.

The NASA mishap investigation board, charged to review the loss of the X-43A Hyper-X program research vehicle during its June 2, 2001 launch, concluded no single factor or potential contributing factor caused the mishap. The flight failed because the vehicle’s control system design was deficient in several analytical modeling areas, which overestimated the system’s margins.

NASA’s Hyper-X program is developing “air breathing” engine technologies that promise performance benefits for future hypersonic aircraft and reusable space launch vehicles. In the X-43A test program, three, 12-foot long, unpiloted vehicles were planned to fly up to 10 times the speed of sound to demonstrate scramjet, or supersonic-combustion ramjet, technologies. The mishap occurred on the first of three planned flights.

For the launch, the X-43A was attached to the nose of a modified Pegasus launch vehicle, which was carried by NASA’s modified B-52 bomber. Seventy-five minutes after takeoff, at an altitude of approximately 24,000 ft., the Pegasus was released. Its solid rocket motor ignited 5.2 seconds later sending the launch vehicle and research vehicle payload on its test flight. Eight seconds later, the vehicle began its planned pitch up maneuver, which was expected to take it to an altitude of approximately 95,000 ft.

Shortly thereafter, the X-43A began to experience a control anomaly characterized by a roll oscillation. At 13.5 seconds after release and at an altitude of approximately 22,000 ft., structural overload of the starboard elevon occurred. The severe loss of control caused the X-43A to deviate significantly from its planned trajectory, and as a result, it was destroyed by range safety 48.6 seconds after release.

The mishap board found the major contributors to the mishap were modeling inaccuracies in the fin actuation system, modeling inaccuracies in the aerodynamics, and insufficient variations of modeling parameters. The flight mishap could only be reproduced when all of the modeling inaccuracies with uncertainty variations were incorporated in the analysis.

“I want to thank the Mishap Investigation Board for their comprehensive and thorough evaluation,” said Dr. Victor Lebacqz, acting Associate Administrator for NASA’s Office of Aerospace Technology. “The findings and recommendations of the board greatly enhance our opportunity for a successful second flight,” he said.

Original Source: NASA News Release

100 Days Until Chinese Space Launch?

The Chinese attempt to launch humans into space might only be 100 days away according to industry insiders. Rumors say that space officials have chosen which astronaut will pilot the mission, Shenzhou-5, but his identity hasn’t been revealed to the public yet. Fourteen astronauts have been in training at the Beijing Aerospace city for many months, but so far all of their identities have been kept secret. The Chinese Space Agency is notorious for secrecy, waiting until after spacecraft have launched before revealing details to the public.

Further Evidence Found for Dark Energy

Image credit: SDSS

Since the discovery several years ago of a mysterious force, called dark energy, which seems to be accelerating the Universe, astronomers have been searching for additional evidence to either support or discount this theory. Astronomers from the Sloan Digital Sky Survey have found fluctuations in cosmic background radiation that match the repulsive influence of dark energy.

Scientists from the Sloan Digital Sky Survey announced the discovery of independent physical evidence for the existence of dark energy.

The researchers found an imprint of dark energy by correlating millions of galaxies in the Sloan Digital Sky Survey (SDSS) and cosmic microwave background temperature maps from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP). The researchers found dark energy’s “shadow” on the ancient cosmic radiation, a relic of cooled radiation from the Big Bang.

With the combination of results from these two large sky surveys, this discovery provides physical evidence for the existence of dark energy; a result that complements earlier work on the acceleration of the universe as measured from distant supernovae. Observations from the Balloon Observations of Millimetric Extragalactic Radiation and Geophysics (BOOMERANG) of Cosmic Microwave Background (CMB) were also part of the earlier findings.

Dark energy, a major component of the universe and one of the greatest conundrums in science, is gravitationally repulsive rather than attractive. This causes the universe’s expansion to accelerate, in contrast to the attraction of ordinary (and dark) matter, which would make it decelerate.

“In a flat universe the effect we’re observing only occurs if you have a universe with dark energy,” explained lead researcher Dr. Ryan Scranton of the University of Pittsburgh’s Physics and Astronomy department. “If the universe was just composed of matter and still flat, this effect wouldn’t exist.”

“As photons from the cosmic microwave background (CMB) travel to us from 380,000 years after the Big Bang, they can experience a number of physical processes, including the Integrated Sachs-Wolfe effect. This effect is an imprint or shadow of dark energy on microwaves. The effect also measures the changes in temperature of cosmic microwave background due to the effects of gravity on the energy of photons”, added Scranton.

The discovery is “a physical detection of dark energy, and highly complementary to other detections of dark energy” added Dr. Bob Nichol, an SDSS collaborator and associate professor of physics at Carnegie Mellon University in Pittsburgh. Nichol likened the Integrated Sachs-Wolfe effect to looking at a person standing in front of a sunny window: “You just see their outline and can recognize them from just this information. Likewise the signal we see has the right outline (or shadow) that we’d expect for dark energy,” said Nichol.

“In particular the color of the signal is the same as the color of the cosmic microwave background, proving it is cosmological in origin and not some annoying contamination,” added Nichol.

“This work provides physical confirmation that one needs dark energy to simultaneously explain both the CMB and SDSS data, independent of the supernovae work. Such cross-checks are vital in science,” added Jim Gunn, Project Scientist of the SDSS and Professor of Astronomy at Princeton University.

Dr. Andrew Connolly of the University of Pittsburgh explained that photons streaming from the cosmic microwave background pass through many concentrations of galaxies and dark matter. As they fall into a gravitational well they gain energy (just like a ball rolling down a hill). As they come out they lose energy (again like a ball rolling up a hill). Photographic images of the microwaves become more blue (i.e. more energetic) as they fall in toward these supercluster concentrations and then become more red (i.e. less energetic) as they climb away from them.

“In a universe consisting mostly of normal matter one would expect that the net effect of the red and blue shifts would cancel. However in recent years we are finding that most of the stuff in our universe is abnormal in that it is gravitationally repulsive rather than gravitationally attractive,” explained Albert Stebbins, a scientist at the NASA/Fermilab Astrophysics Center Fermi National Accelerator Laboratory, an SDSS collaborating institution. “This abnormal stuff we call dark energy.”

SDSS collaborator Connolly said if the depth of the gravitational well decreases while the photon travels through it then the photon would exit with slightly more energy. “If this were true then we would expect to see that the cosmic microwave background temperature is slightly hotter in regions with more galaxies. This is exactly what we found.”

Stebbins added that the net energy change expected from a single concentration of mass is less than one part in a million and researchers had to look at a large number of galaxies before they could expect to see the effect. He said that the results confirm that dark energy exists in relatively small mass concentrations: only 100 million light years across where the previously observed effects dark energy were on a scale of 10 billion light years across. A unique aspect of the SDSS data is its ability to accurately measure the distances to all galaxies from photographic analysis of their photometric redshifts. “Therefore, we can watch the imprint of this effect on the CMB grow as a function of the age of the universe,” Connolly said. “Eventually we might be able to determine the nature of the dark energy from measurements like these, though that is a bit in the future.”

“To make the conclusion that dark energy exists we only have to assume that the universe is not curved. After the Wilkinson Microwave Anisotropy Probe results came in (in February, 2003), that’s a well-accepted assumption,” Scranton explained. “This is extremely exciting. We didn’t know if we could get a signal so we spent a lot of time testing the data against contamination from our galaxy or other sources. Having the results come out as strongly as they did was extremely satisfying.”

The discoveries were made in 3,400 square degrees of the sky surveyed by the SDSS.

“This combination of space-based microwave and ground-based optical data gave us this new window into the properties of dark energy,” said David Spergel, a Princeton University cosmologist and a member of the WMAP science team. “By combining WMAP and SDSS data, Scranton and his collaborators have shown that dark energy, whatever it is, is something that is not attracted by gravity even on the large scales probed by the Sloan Digital Sky Survey.

“This is an important hint for physicists trying to understand the mysterious dark energy,” Spergel added.

In addition to principal investigators Scranton, Connolly, Nichol and Stebbins, Istavan Szapudi of the University of Hawaii contributed to the research. Others involved in the analysis include Niayesh Afshordi of Princeton University, Max Tegmark of the University of Pennsylvania and Daniel Eisenstein of the University of Arizona.

The Sloan Digital Sky Survey ( will map in detail one-quarter of the entire sky, determining the positions and absolute brightness of 100 million celestial objects. It will also measure the distances to more than a million galaxies and quasars. The Astrophysical Research Consortium (ARC) operates Apache Point Observatory, site of the SDSS telescopes.

SDSS is a joint project of The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, University of Pittsburgh, Princeton University, the United States Naval Observatory, and the University of Washington.

Funding for the project has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho and the Max Planck Society.

The WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) is a NASA mission built in partnership with Princeton University and the Goddard Space Flight Center to measure the temperature of the cosmic background radiation, the remnant heat from the Big Bang. The WMAP mission reveals conditions as they existed in the early universe by measuring the properties of the cosmic microwave background radiation over the full sky. (

Original Source: SDSS News Release

Stellar Clusters Found in Milky Way

Image credit: ESO

Astronomers from the European Southern Observatory have found a whole new population of massive newborn stars inside a giant molecular cloud near the centre of the Milky Way. Inside the cloud are four massive stellar clusters with young stars as large as 120 times the mass of our Sun. This region, called W49, is one of the most energetic star forming regions of the Milky Way, and the recent observations help astronomers better understand how these regions form.

Peering into a giant molecular cloud in the Milky Way galaxy – known as W49 – astronomers from the European Southern Observatory (ESO) have discovered a whole new population of very massive newborn stars. This research is being presented today at the International Astronomical Union’s 25th General Assembly held in Sydney, Australia, by ESO-scientist Jo?o Alves.

With the help of infrared images obtained during a period of excellent observing conditions with the ESO 3.5-m New Technology Telescope (NTT) at the La Silla Observatory (Chile), the astronomers looked deep into this molecular cloud and discovered four massive stellar clusters, with hot and energetic stars as massive as 120 solar masses. The exceedingly strong radiation from the stars in the largest of these clusters is “powering” a 20 light-year diameter region of mostly ionized hydrogen gas (a “giant HII region”).

W49 is one of the most energetic regions of star formation in the Milky Way. With the present discovery, the true sources of the enormous energy have now been revealed for the first time, finally bringing to an end some decades of astronomical speculations and hypotheses.

Giant molecular clouds
Stars form predominantly inside Giant Molecular Clouds which populate our Galaxy, the Milky Way. One of the most prominent of these is W49, which has a mass of a million solar masses. It is located some 37,000 light-years away and is the most luminous star-forming region known in our home galaxy: its luminosity is several million times the luminosity of our Sun. A smaller region within this cloud is denoted W49A – this is one of the strongest radio-emitting areas known in the Galaxy.

Massive stars are excessive in all ways. Compared to their smaller and ligther brethren, they form at an Olympic speed and have a frantic and relatively short life. Formation sites of massive stars are quite rare and, accordingly, most are many thousands of light-years away. For that reason alone, it is in general much more difficult to observe details of massive-star formation.

Moreover, as massive stars are generally formed in the main plane of the Galaxy, in the disc where a lot of dust is present, the first stages of such stars are normally hidden behind very thick curtains. In the case of W49A, less than one millionth of the visible light emitted by a star in this region will find its way through the heavy intervening layers of galactic dust and reach the telescopes on Earth.

And finally, because massive stars just formed are still very deeply embedded in their natal clouds, they are anyway not detectable at optical wavelengths. Observations of this early phase of the lives of heavy stars must therefore be done at longer wavelengths (where the dust is more transparent), but even so, such natal dusty clouds still absorb a large proportion of the light emitted by the young stars.

Because of this observational obstacle, nobody had ever looked deep enough into the central most dense regions of the W49A molecular cloud – and nobody really knew what was in there. That is, until Jo?o Alves and his colleague, Nicole Homeier decided to obtain “deep” and penetrating observations of this mysterious area with the SofI near-infrared camera on the 3.5-m New Technology Telescope (NTT) at the ESO La Silla Observatory (Chile).

A series of infrared images was secured during a spell of good weather and very good atmospheric conditions (seeing about 0.5 arcsec). They clearly show the presence of a cluster of stars at the centre of a region of ionized hydrogen gas (an “HII-region”) measuring 20 light-years across. In addition, three other smaller clusters of stars were detected in the image.

Altogether, the ESO astronomers were able to identify more than one hundred heavy-weight stars inside W49A, with masses greater than 15 to 20 times the mass of our Sun. Among these, about thirty are located within the 20 light-year central region and about ten in each of the three other clusters.

The discovery of these hot and massive stars solves a long-standing problem concerning W49A: the exceptional brightness (in astronomical terminology: “luminosity”) of the entire region requires the energetic output from about one hundred massive stars, and nobody had ever seen them. But here they are on the deep and sharp SofI images!
Formation scenarios

The presence of such a large number of very massive stars spread over the entire region suggests that star formation in the various regions of W49A must have happened rather simultaneously from different seeds and not, as some theories propose, by a “domino-type” chain effect where stellar winds of fast particles and the emitted radiation of newly formed massive stars trigger another burst of star formation in the immediate neighbourhood.

The present research results also imply that star formation in W49A began earlier and extends over a larger area than previously thought.

Jo?o Alves is sure that this news will be received with interest by his colleagues: “W49A has long been known to radio astronomers as one of the most powerful star-forming region in the Galaxy with 30 or so massive baby-stars of the O-type, very deeply embedded in their parental cloud. What we have found is in fact quite amazing: this stellar maternity ward is much bigger than we first thought and it has not stopped forming stars yet. We now have evidence for no less than more than one hundred such stars in this region, way beyond the few dozen known until now”.

Nicole Homeier adds: “Above all, we uncovered four massive clusters in there, with stars as massive as 120 times the mass of our Sun – real ‘beasts’ that bombard their surroundings with incredibly intense stellar winds and strong ultraviolet light. This is not a nice place to live – and imagine, this is all inside our so-called ‘quiet Galaxy’!”

Original Source: ESO News Release

NASA Updates Software on FUSE Spacecraft

Image credit: NASA/JHU

NASA’s Far Ultraviolet Spectroscopic Explorer (FUSE) satellite got a complete software upgrade this week to improve the precision of its observations. Software engineers from several groups have been working for two years to upgrade the software for the Attitude Control System, the Instrument Data System, and the processor on the Fine Error Sensor guide camera. The new software will even let the observatory work if some or all of its gyroscopes fail.

NASA’s Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was given a new lease on life following the successful implementation of new software in three computers that work together to control the precision pointing of the telescope.

“We have uploaded new flight software, and can operate FUSE with any number of gyroscopes, including none, if the time comes that all of our gyroscopes fail,” said Dr. George Sonneborn, FUSE project scientist from the NASA Goddard Space Flight Center (GSFC), Greenbelt, Md. “This is a significant conceptual and technical development that brings a new tool to the designers of new and existing satellites, and bodes well for continued FUSE operations,” Sonneborn added.

For the past two years, engineers and scientists at the Johns Hopkins University (JHU) in Baltimore, Orbital Sciences Corporation in Dulles, Va., Honeywell Technical Solutions, Inc., Morris Township, N.J., GSFC, and the Canadian Space Agency, Quebec, have worked together to change the flight software used to point the telescope for science observations.

This involved changing the software aboard all three spacecraft computers: the Attitude Control System, the Instrument Data System, and the processor on the Fine Error Sensor guide camera, provided by the Canadian Space Agency. After extensive testing, the new software, for all three computers, was up linked to the satellite in mid-April 2003.

“I would compare this procedure to performing a brain transplant on a living satellite, but it’s more like a triple brain transplant,” said Dr. William Blair, FUSE chief of observatory operations and a research professor at Johns Hopkins University. “All three computers have to talk and work together properly to make it all work,” he said.

Testing on this new configuration has been ongoing since April, even as normal science observations have been carried out. FUSE can operate on as few as zero gyroscopes, with no degradation in science data quality and only a slight loss of observation scheduling efficiency.

The gyroscopes on board FUSE do not move the satellite, but they provide information on how the spacecraft is moving or drifting over time. FUSE has two packages of three ring-laser gyroscopes. Until the new software was loaded, one operating gyroscope on each of the three axes was needed to conduct normal science operations. FUSE still has this needed configuration, but there has been concern about how long the gyroscopes could last. One gyroscope failed in May 2001, and the five remaining gyroscopes all show signs of age.

FUSE has already survived the loss of two of its four reaction wheels in late 2001. The reaction or momentum wheels are devices that normally allow the satellite to be held steady or moved from one pointing direction to another. Through quick thinking, engineers and scientists modified control software to use devices, called magnetic torquer bars, to provide stability in place of the missing reaction wheels. These devices interact with the Earth’s magnetic field to provide a stabilizing effect on the satellite.

The FUSE satellite, launched in June 1999, is a space telescope that performs high-resolution far-ultraviolet spectroscopy of a broad range of astronomical objects. FUSE observes light at shorter wavelengths than the Hubble Space Telescope can observe, thus providing a complementary capability. Because it has survived a number of close calls, but is still returning excellent science data, the team sometimes refers to FUSE as “the little satellite that could.”

Looking ahead, NASA has just released the call for proposals for new observations with the satellite, during its fifth year of operations, by astronomers from around the world.

The JHU manages FUSE for GSFC and the Office of Space Science at NASA Headquarters in Washington. Partners include the JHU Applied Physics Laboratory, the Canadian Space Agency, the French Space Agency, Honeywell Technical Solutions Inc., and primary spacecraft contractor Orbital Sciences Corporation.

Original Source: NASA News Release

Warped Disk Formed Around Galaxy Centre

Image credit: CfA

Astronomers have found a distant galaxy with a core shaped like a warped pancake around its central supermassive black hole. The disk contains 400,000 times the mass of the Sun, and got its strange shape because the black hole is spewing material in two broad cones. This is different from most black holes, which channel the outflow into a thin, fast-moving jet.

While a person’s shape can be affected by pancakes, especially if you eat too many, you may not expect the same to be true on a cosmic scale. As it turns out, at least for the Circinus spiral galaxy, a pancake can shape an entire galactic nucleus. Astronomer Lincoln Greenhill (Harvard-Smithsonian Center for Astrophysics) and colleagues have found direct evidence for a “pancake” of gas and dust at the center of Circinus — a thin, warped disk surrounding the galaxy’s central, supermassive black hole.

That disk shapes the galaxy’s nucleus. It shadows different regions from the “glare” of the black hole, a glare created by the glow of accreting gas. And when some of this material is blown away from the black hole, as by radiation, the disk channels it, leaving shadowed regions in relative peace. This idea stands in contrast to the prevailing wisdom that shadows and outflows are caused by vast, thick “doughnuts” of dust and gas.

“We caught the Circinus galaxy and its black hole red-handed,” said Greenhill. “Most astronomers think that the center of an active galaxy has an outflow directed and channeled by a doughnut-shaped torus of dust and gas. Our detailed radio images show that the culprit is a warped disk. And if that’s true for the Circinus galaxy, then the same may be true for other active galaxies.”

Greenhill and his fellow astronomers identified the disk using the Australia Telescope Long Baseline Array, which is a network of radio telescopes 600 miles across. Only radio imaging can reveal directly such tiny structures inside galactic nuclei. The Circinus disk in particular is so deeply buried in a jumble of stars, gas, and dust that no optical telescope can detect it. They estimate the disk contains enough mass to form perhaps as many as 400,000 stars like our Sun, were it given a chance.

The Australian array picked up microwave signals from clouds rich in water vapor within both the warped edge-on disk and the outflow. The locations and velocities of the clouds provide strong evidence that the disk is channeling ejected material into two broad cones extending above and below the galactic plane.

“Water masers have been observed in broad, wide-angle outflows in star formation regions within our Galaxy, but this is the first time they have been observed associated with the nuclear region of an active galaxy,” said Simon Ellingsen (University of Tasmania), a co-author of the study. “These observations also are the first to show that this wide-angle outflow originates within about a third of a light-year from the galactic nucleus.”

A black hole is a massive object so compact and with such a powerful gravitational field that nothing can escape its pull once past the black hole’s event horizon. However, material can and does escape from regions near the black hole due to radiation pressure and inefficiencies of the accretion flow, among other things. The escaping material carries away angular momentum, allowing the remaining matter to fall into the black hole. The black hole in Circinus presents a stark contrast to other supermassive black holes whose outflows are channeled into long, narrow jets of material that blast out from the galactic nucleus.

“In the center of the Circinus galaxy, we see a black hole that spews out gas and dust in a broad spray like clouds of vapor from a steam locomotive. This presents us with a paradox. X-ray radiation from the nucleus of Circinus — radiation driven by the black hole — is as intense as for black holes in other active galaxies. In that way, the Circinus black hole appears to be typical. However, while other black holes drive narrow relativistic jets of plasma, the Circinus black hole drives a comparatively meek wind — one that can support the formation of delicate molecules and dust,” said Greenhill.

Greenhill and his colleagues plan to continue studying the nucleus of the Circinus galaxy to investigate the mechanism responsible for generating the outflow.

Original Source: CfA News Release

Kerosene Engine Passes Design Milestone

Image credit: NASA

NASA is working on several next-generation propulsion concepts that could help to push future exploration of the solar system, and one of the furthest along is the RS-84 kerosene-fueled rocket engine. The RS-84 is being designed by the Rocketdyne division of Boeing and it recently passed a detailed technical design review. The final, full-scale prototype engine should be ready for testing in 2007. Kerosene is more compact than traditional hydrogen fuel, saving launch weight, and it’s much safer to handle.

The kerosene-fueled RS-84 engine, one of several technologies competing to power NASA’s next generation of launch vehicles, has successfully completed its preliminary design review.

The RS-84 is a reusable, liquid booster engine that will deliver a thrust level of 1 million pounds of force. The design of the prototype engine is being developed by the Rocketdyne Propulsion & Power Division of the Boeing Company, in Canoga Park, Calif., for NASA’s Next Generation Launch Technology Program.

The program, part of NASA’s Space Launch Initiative, seeks to develop key space launch technologies ? engines and propulsion systems, hardware and integrated launch systems ? that will provide the foundation for America’s future space fleet.

The preliminary design review is a lengthy technical analysis that evaluates engine design according to stringent system requirements. The review ensures development is on target to meet Next Generation Launch Technology program goals: improved safety, reliability and cost. The review is conducted when the engine design is approximately 50 percent complete and engine drawings are approximately 10 percent complete.

“We’ve cleared our first major hurdle and the foundation is set for ensuring delivery of a safe, cost effective engine that will meet the next-generation launch requirements of NASA and the Department of Defense,” said Danny Davis, project manager for the RS-84 project at NASA’s Marshall Space Flight Center in Huntsville, Ala.

“We have a highly experienced team working on this unique design challenge,” Davis added. “I am very proud of the creativity offered by Rocketdyne, and of the thorough, constructive analysis provided by NASA’s insight team.”

The design team’s next major program milestone is the “40k” preburner test, a series of test-firings of a nearly full-scale preburner yielding 40,000 pounds of thrust. The test series, which will be conducted at NASA’s Stennis Space Center in Bay St. Louis, Miss., is scheduled to be completed in September. The final RS-84 prototype is expected to begin full-scale test firing by the end of 2007.

The RS-84 is one of two competing efforts now under way to develop an alternative to conventional, hydrogen-fueled engine technologies. The RS-84 is a reusable, staged combustion rocket engine fueled by kerosene ? a relatively low-maintenance fuel with high performance and high density, meaning it takes less fuel-tank volume to permit greater propulsive force than other technologies. That benefit translates to more compact engine systems, easier fuel handling and loading on the ground, and shorter turnaround time between launches. All these gains, in turn, reduce the overall cost of launch operations, making routine space flight cheaper and more attractive to commercial enterprises.

“No engine yet conceived meets the expectations of high reliability, high reusability mission life and responsiveness that is part of the RS-84 design,” Davis said. “Our design incorporates the latest in materials development, advanced software to monitor and predict problems, and lessons learned from past engine technology efforts.”

“The RS-84 preliminary design was shown to satisfy NASA’s goals, supporting an order of magnitude improvement in safety/reliability and operating cost,” said Roger Campbell, deputy program manager of Boeing Rocketdyne’s RS-84 engine team.

NASA’s Next Generation Launch Technology Program is developing and demonstrating innovative technologies in the areas of propulsion, systems integration and launch operations. The work of the program is intended to yield complete, next-generation space transportation systems that will provide low-cost space access and reinvigorate the U.S. space launch market, enabling stronger competition with international space agencies and private commercial entities, enabling stronger domestic and international competition.

Original Source: NASA News Release