Posted on by Fraser Cain

Wallpaper: Comet NEAT

Image credit: NOAO/AURA/NSF
This image of Comet C/2001 Q4 (NEAT) was taken at the WIYN 0.9-meter telescope at Kitt Peak National Observatory near Tucson, AZ, on May 7, 2004.

The image was taken with the Mosaic I camera, which has a one-square degree field of view, or about five times the size of the Moon. Even with this large field, only the comet?s coma and the inner portion of its tail are visible. This color image was assembled by combining images taken through blue, green and red filters.

A small star cluster (C0736-105, or Melotte 72) is visible in the lower right of the image, between the head of the comet and the bright red star in the lower-right corner.

Comet C/2001 Q4 (NEAT) was discovered on August 24, 2001, by the Near Earth Asteroid Tracking (NEAT) system operated by NASA?s Jet Propulsion Laboratory, Pasadena, CA.

The comet will remain visible for several weeks with binoculars and small telescopes just after sunset, high in the western sky.

Image Credit: T. Rector (University of Alaska Anchorage), Z. Levay and L.Frattare (Space Telescope Science Institute) and WIYN/NOAO/AURA/NSF

Original Source: NOAO News Release

Posted on by Fraser Cain

Progress Launches to Supply Station

Image credit: Energia
In compliance with the International Space Station (ISS) flight program and obligations of the Russian Party under the ISS Project rocket and space complex Soyuz-U/Progress M-49 was launched at 16:34:23 Moscow summer time from Baikonur cosmodrome.

The aim of the launch is to deliver necessary cargoes to the ISS to continue operation of the Orbital Complex and create habitation and working conditions for the crew.

According to the ISS assembly program, the Progress M-49 flight designation is 14P.

The refueling compartment of Progress M-49 contains about 640 kg of propellant, 28 kg of oxygen, 20 kg of air, 420 kg of potable water. Its cargo compartment accommodates about 1.2 tons of dry cargoes including food products, equipment and aids for the station onboard systems, individual protection gear, sets of crew procedures, video and photo equipment, parcels for the crew, structural elements, payloads for the US On-Orbit Segment, hardware and materials for space experiments.

The vehicle was launched into orbit with maximum altitude of 252.0 km, minimum altitude of 193.1 km, period of revolution of 88.65 min and inclination of 51.66?.

The vehicle onboard systems operate normally.

The vehicle and ISS docking is scheduled on 27 May 2004 with berthing to the axial docking port of Russian Service Module Zvezda. The estimated time of the docking assembly contact is 17:55. Cargo vehicle Progress M1-11, that has been operating as part of the Orbital Complex since 31 May 2004, cleared the docking port on 24 May 2004. This vehicle that was transferred to a safe distance after the docking will continue its on-orbit flight during the following ten days under a permanent control of MCC-M specialists, supporting performance of the science experiments under the autonomous flight program. Following that, it will be transferred to the descent trajectory and deorbit in the assigned area of the Pacific Ocean.

The decision about complex Soyuz-U/ProgressM-49 launch was taken by the Government Board (co-chairmen: N.F. Moiseev, V.A. Grin’) based on the conclusion of the Technical Management about the readiness of the Space Complex and ground infrastructure components involved in the ISS program implementation.

The prelaunch processing was directly led by the Technical Management (Yu.P. Semenov, Technical Manager of Russian Piloted Space Programs, General Designer of S.P. Korolev RSC Energia, Academician of the Russian Academy of Sciences).

The vehicle and Space Station flight is under control of the Lead Operational Control Team (LOCT) located in the Mission Control Center in Moscow (MCC-M), Korolev, Moscow area (Flight Director is pilot-cosmonaut V.A. Soloviev, S.P. Korolev RSC Energia).

The ISS Orbital Complex operates in orbit with the following parameters: maximum altitude of 385.6 km, minimum altitude of 359.5 km, period of revolution of 91.8 min and inclination of 51.65?. The Russian Segment consists of Functional Cargo Module Zarya, Service Module Zvezda, docking module Pirs, manned transport spacecraft Soyuz TMA-4. The US On-orbit Segment consists of modules Unity and Destiny, airlock Quest, multi-link truss structure with deployed solar arrays. Total mass of the ISS is about 175.2 tons.

According to the telemetry information and reports made by the ISS Expedition 9 crew (ISS-9): Russian cosmonaut Gennady Padalka (commander) and US astronaut Mike Fincke (flight engineer), all station onboard systems operate in the designed modes.

The Space Station is ready for docking with a new cargo vehicle.

Original Source: Energia News Release

Posted on by Fraser Cain

Quasars Come From Stable Homes

Image credit: PPARC
Quasars, the most brilliant of cosmic fireworks, appear to shine forth from humdrum galaxies in the early universe, not the giant or disrupted ones astronomers expected. This is according to a team of Australian, Canadian and UK astronomers who studied an assortment of quasars near the edge of the observable universe using the Frederick C. Gillett Gemini North Telescope on Hawaii’s Mauna Kea. Their findings were presented today (May 25th) at the first Gemini Science Conference by Dr David Schade of the National Research Council, Canada.

The quasars’ pedestrian surroundings came as a shock. “It’s like finding a Formula One racing car in a suburban garage,” said Dr Scott Croom of the Anglo-Australian Observatory in Australia who led the study. Put another way, “On our previous idea that brighter Quasars should inhabit brighter host galaxies, these observations were a bit of an insult to the superb

Gemini North telescope! These observations should really have been like using a magnifying glass to find an elephant. Instead, these host galaxies turned out to be more like little mice, despite their brilliant roar!” said team-member Professor Tom Shanks from the University of Durham (UK).

It is thought that quasars are located in the central cores of galaxies where matter falling onto a supermassive black hole is turned into a blinding torrent of radiation. Quasars flourished when the universe was between a tenth and a third of its present age.

“This finding is particularly exciting because it means that we may need to re-think our models of how quasars work. This isn’t the first time quasars have done this to us, it seems that quasars like to keep us guessing!” said Dr. Schade.

The research team attempted to obtain some of the first-ever detailed infrared views of the host galaxies-nine in all-each about 10 billion light-years away. “We’d hoped their sizes and shapes might give clues as to what triggered quasar activity,” said Dr Croom. Instead, the team found that all but one of the galaxies were too faint or small to detect, even though the data’s sensitivity and resolution were exceptionally high. The one convincing detection was remarkably unremarkable, similar in brightness and size to our own Galaxy.

Many astronomers had anticipated that a quasar’s host galaxy would be large, and might show signs of having collided with another galaxy-violence that could spark a quasar into brilliance. The team’s finding will undoubtedly add fuel to the debate regarding how galaxies and black holes form and grow.

Astronomers have used other telescopes, on the ground and in space to look for very distant quasar host galaxies but the results have been inconclusive. “For this study, the Gemini telescope was able to produce an image sharpness that is usually only possible by using the Hubble Space Telescope,” said Professor Shanks. “But Gemini’s larger mirror can collect ten times more light to study faint objects.” The image detail was achieved with a technology called adaptive optics to remove distortions to starlight caused by atmospheric turbulence.

This combination provided a powerful capability that produced some of the deepest (faintest) and sharpest infrared images ever obtained of objects in the early universe.

One of the difficulties inherent in this study was to find quasars that were close to the relatively bright guide stars necessary to use adaptive optics technology. To find the necessary sample size, the team drew on a database of more than 20,000 quasars gathered with the Anglo-Australian Telescope between 1997 and 2002. This work represents the largest quasar survey ever attempted and, “the only one in which we could hope to find a decent sample of quasars to meet our requirements,” said Dr. Croom.

Original Source: PPARC News Release

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More Information About Icy Moons Mission

Image credit: NASA/JPL
NASA has issued its mission design requirements to three industry teams for a proposed mission to Jupiter and its three icy moons. The requirements are also the first product formulated by NASA’s new Office of Exploration Systems in Washington.

The Jupiter Icy Moons Orbiter is a spacecraft with an ambitious proposed mission that would orbit three planet-sized moons of Jupiter — Callisto, Ganymede and Europa — that may harbor vast oceans beneath their icy surfaces. The mission would be powered by a nuclear reactor and launched sometime in the next decade.

Associate Administrator retired Rear Adm. Craig E. Steidle of NASA’s Office of Exploration Systems said, “The Jupiter Icy Moons Orbiter requirements represent our new way of doing business, tracing exploration strategies to the technology maturation programs that will enable this exciting mission and the other missions that make up Project Constellation.”

The Request for Proposal was released this week to the three previously qualified industry teams led by Boeing, Huntington Beach, Calif.; Lockheed Martin, Denver; and Northrop Grumman, Redondo Beach, Calif. These three companies are currently working under study contracts investigating conceptual designs for the mission. The proposals are due July 16, 2004.

The scope of the initial contract is to co-design the spacecraft through the preliminary design with the government team. A contract modification will be issued after preliminary design to implement the design, to integrate and test the spacecraft and to integrate the spacecraft with the reactor module and mission module. JPL would be responsible for delivering the mission module, which would include instruments procured competitively via a NASA announcement of opportunity. The launch vehicle will be supplied by NASA. The Department of Energy’s Office of Naval Reactors would be responsible for the reactor module. To ensure the technologies demonstrated are consistent and coordinated with the Vision for Space Exploration, Project Constellation is managed within the Office of Exploration Systems.

“Although the Jupiter Icy Moons Orbiter mission may not launch until the next decade, the study of revolutionary new technologies in spacecraft design is underway in the areas of power conversion and heat rejection, electric propulsion, radiation hardened electronics and materials, and telecommunications,” said Karla Clark, industry studies lead and deep space avionics project manager for the Jupiter Icy Moons Orbiter Mission.

Three cross-cutting science themes identified by the NASA- chartered science definition team would drive the proposed Jupiter Icy Moons Orbiter science investigations. The themes are to evaluate the degree to which subsurface oceans are present on these worlds; to study the chemical composition of the moons, including organic materials, and the surface processes that affect them; and to scrutinize the entire Jupiter system, particularly the interactions between Jupiter and the moons’ atmospheres and interiors.

“The scientists have told us what they want,” said John Casani, project manager for the Jupiter Icy Moons Orbiter mission at JPL. “When you consider the five-to-eight year trip to Jupiter, going from one moon to the next, not only flying by but orbiting each moon, this will require a unique nuclear power and electric propulsion system. The large amount of power required for electric propulsion could be used in orbit to power a significantly enhanced suite of instruments not even conceivable with previous power systems.”

The Jupiter Icy Moons Orbiter mission is part of NASA’s Project Prometheus, a program studying a series of initiatives to develop power systems and technologies for space exploration. The Jupiter Icy Moons Orbiter, managed by JPL, would be the first NASA mission utilizing nuclear electric propulsion, which would enable the spacecraft to orbit each of these icy worlds to perform extensive investigations of their makeup, history and potential for sustaining life. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the proposed Jupiter Icy Moons Orbiter mission for NASA’s Office of Exploration Systems, Washington, D.C.

For more information visit: http://spacescience.nasa.gov/missions/prometheus.htm or: NASA JIMO Mission

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Rosetta Focuses on LINEAR

Image credit: ESA
ESA’s comet-chaser Rosetta, whose 10-year journey to its final target Comet 67P/Churyumov-Gerasimenko started on 2 March, is well on its way. The first phase of commissioning is close to completion and Rosetta has successfully performed its first scientific activity – observation of Comet Linear.

The commissioning activities, which started a couple of days after launch, included the individual activation of all instruments on board the Rosetta orbiter and the Philae lander. This first check-out worked flawlessly and showed that the spacecraft and all instruments are functioning well and in excellent shape.

The commissioning tests also paved the way for Rosetta’s first scientific activity: observation of Comet C/2002 T7 (LINEAR), which is currently travelling for the first and only time through the inner Solar System and offered Rosetta an excellent opportunity to make its first scientific observation.

On 30 April, the OSIRIS camera system, which was scheduled for commissioning on that date, took images of this unique cometary visitor. Later that day, three more instruments on board Rosetta (ALICE, MIRO and VIRTIS) were activated in parallel to take measurements of the comet. Although the parallel activation of the instruments was not planned until later in the year, the Rosetta team felt confident that this could be done without any risk because of the satisfactory progress of the overall testing.

The first data from the remote-sensing observations confirm the excellent performance of the instruments. The four instruments took images and spectra of Comet C/2002 T7 (LINEAR) to study its coma and tail in different wavelengths, from ultraviolet to microwave. Rosetta successfully measured the presence of water molecules in the tenuous atmosphere around the comet. Detailed analysis of the data will require the complete calibration of the instruments, which will take place in the coming months. The OSIRIS camera produced high-resolution images of Comet C/2002 T7 (LINEAR) from a distance of about 95 million kilometres. The image (above) showing a pronounced nucleus and a section of the tenuous tail extending over about 2 million kilometres was obtained by OSIRIS in blue light.

The successful observation of Comet Linear was a first positive test for Rosetta’s ultimate goal, Comet 67P/Churyumov-Gerasimenko, which will be reached in 2014. Rosetta will be the first mission to undertake a long-term exploration of a comet at close quarters whilst accompanying it on its way towards the Sun.

The unprecedented in-depth study conducted by the Rosetta orbiter and its Philae lander will help scientists decipher the formation of our Solar System around 4600 million years ago and provide them with clues of how comets may have contributed to the beginning of life on Earth. In particular, the Philae lander, developed by a European consortium under the leadership of the German Aerospace Research Institute (DLR), will analyse the composition and structure of the comet’s surface.

After Rosetta’s first deep-space manoeuvres were carried out on 10 and 15 May with the highest accuracy, the first phase of commissioning is set to be completed in the first week of June. Rosetta will then go into a quiet ?cruise mode? until September, when the second phase of commissioning is scheduled to start. These activities, including the interference and pointing campaign, will last until December.

So the Rosetta spacecraft is well under way on its epic 10-year voyage, to do what has never before been attempted ? orbiting and landing on a comet.

Original Source: ESA News Release

Posted on by Fraser Cain

Swirls on Saturn

Image credit: NASA/JPL/Space Science Institute
Dramatic details are visible in the swirling turbulent bands of clouds in Saturn?s atmosphere. Particularly noteworthy is the disturbed equatorial region. The image was taken with the narrow angle camera in spectral region where methane strongly absorbs light on May 10, 2004 at a distance of 27.2 million kilometers (16.9 million miles) from Saturn. Image scale is 162 kilometers (101 miles) per pixel. Contrast in the image was enhanced to aid visibility.

The Cassini-Huygens mission 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 Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: CICLOPS News Release

Posted on by Fraser Cain

Heaviest Stars are Twins

Image credit: Harvard-Smithsonian CfA
About 20,000 light-years from Earth, two massive stars grapple with each other like sumo wrestlers locked in combat. Both giants, each weighing in at around 80 times the mass of our Sun, are the heaviest stars ever. They orbit each other every 3.7 days, nearly touching as they spin on the celestial stage. And they lead tempestuous lives worthy of any Hollywood couple, blasting each other with hot, violent stellar winds.

“We could not resist exploring this system because it’s so remarkable. It’s a place of true extremes,” said astronomer Alceste Bonanos (Harvard-Smithsonian Center for Astrophysics).

The binary star system Bonanos studied, known as WR 20a, was pegged as particularly interesting only weeks ago by a team of European researchers headed by Gregor Rauw. That team’s spectroscopic observations showed that both stars were very massive. However, the only way to determine the masses precisely was to establish at what angle we were viewing the system, as well as the orbital period.

Bonanos and her advisor, Krzysztof Stanek (CfA), requested photometric observations from the Optical Gravitational Lensing Experiment (OGLE) team led by Andrzej Udalski (Warsaw University Observatory). Bonanos and Stanek knew that if the system were nearly edge-on, one star would periodically pass in front of, or eclipse, the other. Fortuitously, those eclipses were detected by the OGLE group, thereby firmly establishing the characteristics of the system.

“When we realized how important it would be to obtain an accurate light curve for WR 20a, we immediately decided to contact Andrzej Udalski, who leads the Polish project known as OGLE. They are a premier facility for optical surveys, and we were very happy when they agreed to collaborate on this project,” said Stanek.

Observations were collected in May 2004 with the 1.3-meter-diameter OGLE telescope at the Las Campanas Observatory in Chile.

“The results have exceeded our expectations; after just two nights, we realized that the star significantly changed its brightness, and after a few more we were certain that the system is eclipsing,” said Udalski.

“After obtaining data each night for more than two weeks, we were able to measure very accurately the period, inclination angle, and hence the masses of the two stars,” added Stanek.

A System Of Extremes
WR 20a is part of the Westerlund 2 star cluster, which resides in a region of ionized hydrogen left over from the cluster’s formation in the constellation Carina. WR 20a contains two hot, young Wolf-Rayet stars-a type of star that is extremely rare and short-lived.

“Wolf-Rayet stars are likely progenitors of the extremely powerful explosions known as gamma-ray bursts,” said Bonanos. “These stars are already 2 or 3 million years old. In another few million years, whichever one is slightly more massive will undergo core collapse and blast off its outer layers. The companion star likely will survive despite its nearness, at least until it goes supernova sometime later.”

While other stars, such as the Pistol Star and eta Carinae, are suspected of containing enough material to make more than 100 Suns, their masses have not been determined accurately. The possibility exists that they are simply very close binaries. WR 20a is the most massive known binary system where both stars have precisely determined masses.

“It is important to study and understand these massive stars because they probe the realm of the first stars that formed in the Universe. Learning more about this system will help improve star formation models, as well as increase our understanding of the connection of these stars to supernovae and gamma-ray bursts,” said Stanek.

This research has been posted online at http://arxiv.org/abs/astro-ph/0405338 in a paper co-authored by Alceste Bonanos and Krzysztof Stanek (CfA); with Andrzej Udalski, Lukasz Wyrzykowski, Karol Zebrun, Marcin Kubiak, Michal Szymanski, Olaf Szewczyk, Grzegorz Pietrzynski, and Igor Soszynski (Warsaw University Observatory).

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: Harvard CfA News Release

Posted on by Fraser Cain

Asteroid Wiped Out the Dinosaurs in Hours

Image credit: NASA
According to new research led by a University of Colorado at Boulder geophysicist, a giant asteroid that hit the coast of Mexico 65 million years ago probably incinerated all the large dinosaurs that were alive at the time in only a few hours, and only those organisms already sheltered in burrows or in water were left alive.

The six-mile-in-diameter asteroid is thought to have hit Chicxulub in the Yucatan, striking with the energy of 100 million megatons of TNT, said chief author and Researcher Doug Robertson of the department of geological sciences and the Cooperative Institute for Research in Environmental Sciences. The “heat pulse” caused by re-entering ejected matter would have reached around the globe, igniting fires and burning up all terrestrial organisms not sheltered in burrows or in water, he said.

A paper on the subject was published by Robertson in the May-June issue of the Bulletin of the Geological Society of America. Co-authors include CU-Boulder Professor Owen Toon, University of Wyoming Professors Malcolm McKenna and Jason Lillegraven and California Academy of Sciences Researcher Sylvia Hope.

“The kinetic energy of the ejected matter would have dissipated as heat in the upper atmosphere during re-entry, enough heat to make the normally blue sky turn red-hot for hours,” said Robertson. Scientists have speculated for more than a decade that the entire surface of the Earth below would have been baked by the equivalent of a global oven set on broil.

The evidence of terrestrial ruin is compelling, said Robertson, noting that tiny spheres of melted rock are found in the Cretaceous-Tertiary, or KT, boundary around the globe. The spheres in the clay are remnants of the rocky masses that were vaporized and ejected into sub-orbital trajectories by the impact.

A nearly worldwide clay layer laced with soot and extra-terrestrial iridium also records the impact and global firestorm that followed the impact.

The spheres, the heat pulse and the soot all have been known for some time, but their implications for survival of organisms on land have not been explained well, said Robertson. Many scientists have been curious about how any animal species such as primitive birds, mammals and amphibians managed to survive the global disaster that killed off all the existing dinosaurs.

Robertson and colleagues have provided a new hypothesis for the differential pattern of survival among land vertebrates at the end of the Cretaceous. They have focused on the question of which groups of vertebrates were likely to have been sheltered underground or underwater at the time of the impact.

Their answer closely matches the observed patterns of survival. Pterosaurs and non-avian dinosaurs had no obvious adaptations for burrowing or swimming and became extinct. In contrast, the vertebrates that could burrow in holes or shelter in water — mammals, birds, crocodilians, snakes, lizards, turtles and amphibians — for the most part survived.

Terrestrial vertebrates that survived also were exposed to the secondary effects of a radically altered, inhospitable environment. “Future studies of early Paleocene events on land may be illuminated by this new view of the KT catastrophe,” said Robertson.

Original Source: CU-Boulder News Release

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Binary Black Holes Modeled on Computer

Image credit: Penn State
Scientists at Penn State have reached a new milestone in the effort to model two orbiting black holes, an event expected to spawn strong gravitational waves. “We have discovered a way to model numerically, for the first time, one orbit of two inspiraling black holes,” says Bernd Bruegmann, Associate Professor of Physics and a researcher at Penn State’s Institute for Gravitational Physics and Geometry. Bruegmann’s research is part of a world-wide endeavor to catch the first gravity wave in the act of rolling over the Earth.

A paper describing these simulations will be published in the 28 May 2004 issue of the journal Physical Review Letters. The paper is authored by Bruegmann and two postdoctoral scholars in his group at Penn State, Nina Jansen and Wolfgang Tichy.

Black holes are described by Einstein’s theory of general relativity, which gives a highly accurate description of the gravitational interaction. However, Einstein’s equations are complicated and notoriously hard to solve even numerically. Furthermore, black holes pose their very own problems. Inside each black hole lurks what is known as a space-time singularity. Any object coming too close will be pulled to the center of the black hole without any chance to escape again, and it will experience enormous gravitational forces that rip it apart.

“When we model these extreme conditions on the computer, we find that the black holes want to devour and to tear apart the numerical grid of points that we use to approximate the black holes,” Bruegmann says. “A single black hole is already difficult to model, but two black holes in the final stages of their inspiral are vastly more difficult because of the highly non-linear dynamics of Einstein’s theory.” Computer simulations of black hole binaries tend to go unstable and crash after a finite time, which used to be significantly shorter than the time required for one orbit.

“The technique we have developed is based on a grid that moves along with the black holes, minimizing their motion and distortion, and buying us enough time for them to complete one spiraling orbit around each other before the computer simulation crashes,” Bruegmann says. He offers an analogy to illustrate the “co-moving grid” strategy: “If you are standing outside a carousel and you want to watch one person, you have to keep moving your head to keep watching him as he circles. But if you are standing on the carousel, you have to look in only one direction because that person no longer moves in relation to you, although you both are going around in circles.”

The construction of a co-moving grid is an important innovation of Bruegmann’s work. While not a new idea to physicists, it is a challenge to make it work with two black holes. The researchers also added a feedback mechanism to make adjustments dynamically as the black holes evolve. The result is an elaborate scheme that actually works for two black holes for about one orbit of the spiraling motion.

“While modelling black hole interactions and gravitational waves is a very difficult project, Professor Bruegmann’s result gives a good view of how we may finally succeed in this simulation effort,” says Richard Matzner, Professor at the University of Texas at Austin and principal investigator of the National Science Foundation’s former Binary Black Hole Grand Challenge Alliance that laid much of the groundwork for numerical relativity in the 90’s.

Abhay Ashtekar, Eberly Professor of Physics and Director of the Institute for Gravitational Physics and Geometry, adds, “The recent simulation of Professor Bruegmann’s group is a landmark because it opens the door to performing numerical analysis of a variety of black hole collisions which are among the most interesting events for gravitational wave astronomy.”

This research was funded by grants from the National Science Foundation including one to the Frontier Center for Gravitational Wave Physics established by the National Science Foundation in the Penn State Institute for Gravitational Physics and Geometry.

Original Source: Penn State News Release

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Gravity Probe B’s First Month in Space

Image credit: NASA
One month into the Gravity Probe B mission ? a NASA experiment to test two predictions of Albert Einstein’s Theory of General Relativity ? all spacecraft subsystems continue to perform well, and the spacecraft orbit is stable. . Gravity Probe B is managed by the Marshall Center.

One month into the mission, all spacecraft subsystems are continuing to perform well. The spacecraft’s orbit remains stable and meets our requirements for next month’s transition into the science phase of the mission, upon completion of the spacecraft initialization and orbit checkout. The four gyroscopes are suspended, and we have indications that they are rotating slightly in their housings.

Last weekend, the team successfully performed a procedure to reduce magnetic flux that had built up around the gyroscope rotors (spheres). Magnetic flux is a measure of the number of magnetic field lines penetrating a surface. To ensure that the SQUID readouts receive clean signals from the gyroscopes and to provide the highest possible degree of accuracy during the GP-B science experiment, any magnetic flux around the gyroscope rotors must be minimized.

We reduce magnetic flux by turning on heaters and flowing helium gas, warmed to 10 Kelvin, through the probe. This process also drives off any residual helium remaining in the well of the Dewar, where the probe sits. The flux reduction procedure went smoothly, and when it was completed, the level of trapped flux remaining within the gyros was almost imperceptible. In fact, gyroscope #4, which previously had the highest amount of trapped magnetic flux of all the gyros now has the lowest level.

The flux reduction procedure added heat to the Dewar, thereby increasing the pressure inside to its maximum allowable level. The increased pressure during this stress period caused some of the spacecraft’s micro thrusters to become unstable, resulting in the spacecraft pointing in the wrong direction and triggering a “safemode.”

The 16 micro thrusters are arranged in clusters of four, and local feedback loops within each cluster enable the thrusters to communicate with each other and automatically adjust their flow rates. Ground commands were issued to isolate the unstable thrusters, which resolved the thruster cross-talk issue and enabled the spacecraft to re-orient itself. The thrusters are now functioning properly, the spacecraft’s attitude has been corrected, and it is once again pointing towards the guide star.

The flux reduction operation and subsequent thruster instability and attitude problems has delayed locking the spacecraft onto the guide star, which will be our next major activity. While we have used up some of the contingency days built into the Initialization & Orbit Checkout (IOC) schedule, this phase of the Gravity Probe B mission is still on track for completion within 60 days after launch, at which time the 13-month science data collection will begin. This will be followed by a two-month final calibration of the science instrument assembly.

NASA’s Gravity Probe B mission, also known as GP-B, will use four ultra-precise gyroscopes to test Einstein’s theory that space and time are distorted by the presence of massive objects. To accomplish this, the mission will measure two factors ? how space and time are warped by the presence of the Earth, and how the Earth’s rotation drags space-time around with it.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Gravity Probe B program for NASA’s Office of Space Science. Stanford University in Stanford, Calif., developed and built the science experiment hardware and operates the science mission for NASA. Lockheed Martin of Palo Alto, Calif., developed and built the GP-B spacecraft.

Original Source: NASA News Release