Posted on by Fraser Cain

Cassini Arrives at Saturn Safely

After a seven-year cruise through the Solar System, the joint NASA/ESA/ASI Cassini-Huygens spacecraft last night successfully entered orbit around Saturn.

The Cassini orbiter is now ready to begin its four-year survey of the planet and its moons, while the Huygens probe will be prepared for the next major mission milestone: its release toward the largest moon, Titan, in December.

?This shows international space co-operation at its best,? said ESA?s Director of Science, Prof. David Southwood, after confirmation of the orbit insertion. ?Few deep space planetary missions have carried the hopes of such a large community of scientists and space enthusiasts around the world. Congratulations to the teams in the US and Europe who made this possible and to all participants in the programme, who have a lot to do over the years ahead.?

The Saturn Orbit Insertion was the last and most critical manoeuvre performed by the spacecraft to achieve its operational orbit. If it had failed, the spacecraft would have just flown past Saturn and got lost in the outer Solar System.

Cassini-Huygens was launched from Cape Canaveral, Florida, on 15 October 1997, atop a Titan 4B/Centaur, the most powerful expendable launch vehicle in the US fleet at the time. To reach Saturn it had to perform a series of gravity assist manoeuvres around Venus (April 1998 and June 1999), Earth (August 1999) and Jupiter (December 2000).

Last night, Cassini-Huygens approached Saturn from below the plane of its rings. Using its high-gain antenna dish as a shield to protect its fragile body from dust impacts, it first crossed the ring plane at 02:03 UT, some 158 500 kilometres from the centre of Saturn, in the gap that separates the F ring from the G ring. About 25 minutes later, at 02:36 UT, the probe fired one of its twin main engines for a 96-minute burn to enter orbit. The signal confirming this ignition took 84 minutes to reach Earth, some 1500 million kilometres from Saturn.

The burn went smoothly and reduced Cassini-Huygens?s relative velocity to Saturn while the probe passed only 19 000 kilometres from the planet?s upper clouds. After completion of the burn, the probe was tilted first toward Earth to confirm insertion and then toward Saturn?s rings in order to take close-up pictures as it flew only a few thousand kilometres above them. This was a unique opportunity to attempt to discriminate individual components within the rings, as Cassini is not planned to come this close to them again. The orbiter?s instruments also took advantage of its proximity to the planet to make an in-depth study of its atmosphere and environment.

A second crossing of the ring plane took place at 05:50 UT.

The spacecraft is in perfect shape to begin its tour of the Saturnian system with at least 76 orbits around the ringed planet and 52 close encounters with seven of its 31 known moons. This tour actually began before insertion with a close fly-by of an eighth moon, Phoebe, on 11 June. The primary target for Cassini-Huygens will be the largest of these moons, Titan, with a first fly-by at an altitude of 1200 kilometres on 26 October.

During the coming months, ESA?s scientists will prepare for the release of their main contribution to the mission, the Huygens probe, which will be released on 25 December to enter the atmosphere of Titan on 14 January 2005. Built for ESA by an industrial team led by Alcatel Space, this 320 kilogram probe carries six science instruments to analyse and characterise the atmosphere and its dynamics during its descent. If the probe survives the impact on reaching the surface, it will also analyse the physical properties of its environment after landing.

Actually bigger than Mercury, Titan features a hazy nitrogen-rich atmosphere containing carbon-based compounds. The chemical environment on Titan is thought to be similar to that of Earth before life, although colder (-180?C) and lacking liquid water. The in situ results from Huygens, combined with global observations from repeated fly-bys of Titan by the Cassini orbiter, are expected to help us understand the evolution of the early Earth’s atmosphere and provide clues about the mechanisms that led to the dawn of life on our planet.

The Cassini orbiter, the largest and most complex deep-space vehicle ever launched, carries 12 science instruments developed by US and international teams to conduct in-depth studies of Saturn, Titan, the icy moons, the ring system and the magnetospheric environment. Two of the orbiter?s instruments were provided by Europe.

?More than twenty years have passed since Pioneer 11 and the Voyagers gave us a first glimpse of Saturn, as they crossed this complex system in only a few days,? explained Prof. Southwood, who is also principal investigator for Cassini?s magnetometer. ?Now, with Cassini, we are here to stay, watch and investigate. And with Huygens we will go even deeper and further, not only plunging into an extraterrestrial atmosphere but also an atmosphere like the early Earth?s. This means we are travelling billions of years back into our own past to investigate one of the Universe?s best kept secrets: where we came from.?

The Cassini-Huygens mission is a co-operation between NASA, ESA, the European Space Agency and ASI, the Italian space agency. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, is managing the mission for NASA?s Office of Space Science, Washington.

Original Source: ESA News Release

Posted on by Fraser Cain

Cassini Will Arrive Today

Saturn is now a day away for the Cassini spacecraft, a seasoned traveler that began its journey nearly seven years ago.

On June 30 at 7:36 p.m. Pacific Time (10:36 p.m. EDT), Cassini will begin executing a series of commands to enter orbit around the ringed planet. The spacecraft will fire its main engine for a crucial 96 minutes to slow down and be captured in orbit about Saturn.

Besides launch, orbit insertion is the next most critical part of the mission. “Everything has to go just right. The burn must occur for all 96 minutes, the turns must occur at the right time, the computers must keep the sequence going even in the event something unexpected should happen,” said Robert T. Mitchell, program manager for the Cassini-Huygens mission at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “The spacecraft has been programmed to continue even in the event of an emergency. With a one-way light time of 1 hour and 24 minutes, we had to teach the spacecraft to take care of itself. We don’t want Cassini to call home if a problem arises, we want it to keep going. That is precisely what we’ve told the spacecraft: Don’t stop, keep going until you’ve put in all 96 minutes of burn,” he said.

During the orbit insertion, Cassini will fly closer to Saturn than at any other time during the spacecraft’s planned four-year tour of Saturn. This provides an unprecedented opportunity to study the planet and rings at close range. It will pass approximately 20,000 kilometers (12,427 miles) above Saturn’s cloud tops, closer than any other spacecraft in history. It will also be flying about 10 times closer to the rings than at any other point in the mission

Cassini carries 12 instruments that will study the planet, rings and moons in extensive detail. Riding aboard Cassini is a second spacecraft, the Huygens probe, built by the European Space Agency. It carries half a dozen instruments that will study Titan, Saturn’s largest moon, a prime target for both Cassini and the Huygens probe. Titan is the only moon in the solar system to have a dense atmosphere and resembles the early Earth in deep freeze.

“In a sense, Cassini and the Huygens probe are like time machines that will take us back to examine a world we’ve never seen before, a world that may resemble what our own world was like 4.5 billion years ago,” said Dr. Jean-Pierre Lebreton of the European Space Agency, who is mission manager and project scientist for the Huygens probe.

Eighty-five minutes before the engine burn, Cassini will rotate to point its main antenna dish forward. The Italian-built antenna, 4 meters (13 feet) in diameter, will offer shielding against dust particles the spacecraft may hit as it crosses a gap in the rings. The spacecraft will continue transmitting a monotone “carrier” signal with a secondary antenna for tracking from Earth. Cassini will pass twice through a known gap between the F and G rings, first while ascending shortly before the burn, then while descending shortly after the burn.

The engine burn will slow the spacecraft by 626 meters per second (1,400 miles per hour). Five science instruments will be on during the burn, and others will be used shortly after the engine cuts off. The magnetometer will measure the strength and direction of the magnetic field to understand the physics of Saturn’s magnetic dynamics. Lightning may also be detected. Another instrument will provide a record of the dust hits as the spacecraft flies through the ring plane. These observations may tell scientists the size of these tiny particles and the thickness of that ring region. The remote sensing instruments will assess the rings’ composition, temperature, and structure. Then the spacecraft will be oriented for the outbound ring plane crossing. After crossing the ring plane in the descending mode, Cassini will look back at the sunlit face of the rings to take more data before turning to Earth to transmit its data.

“Should something happen during the burn, the science sequence will stop,” said Dr. Dennis Matson, project scientist for the Cassini-Huygens mission at JPL. “We are prepared to live with this outcome. Getting into orbit is the priority. Getting the science is extra credit.”

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. JPL designed, developed and assembled the Cassini orbiter. For the latest images and more information about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

How About Mobile Lunar Bases?

Landing mobile bases on the moon is an idea whose time has come, according to a NASA researcher.

Lunar bases that can travel on wheels, or even legs, will increase landing zone safety, provide equipment redundancy and improve the odds of making key discoveries by enabling crews to visit many lunar sites, according to Marc Cohen, a researcher at NASA’s Ames Research Center, in California’s Silicon Valley. Cohen recently presented his concept in a research paper at the 2004 American Institute of Physics Forum in Albuquerque, N.M.

“If you set up a base at a fixed location on the moon, you are very limited in the sites of scientific interest that you can reach,” Cohen said. “What it comes down to is if you’re landing a habitat on legs and wheels, it doesn’t take a lot more investment to make it highly mobile, provided you have enough energy resources that would enable it to travel great distance across the moon with or without the crew onboard,” Cohen explained.

Linked mobile moon habitats might travel like treaded trains without tracks, or they could cross the moonscape in a line like Conestoga wagons crossing the American West. Walking or rolling habitats could dock to one another, or circle close together, when they reach a rest or research site, according to designs suggested by engineers over that last three decades, Cohen noted.

In contrast, a common scenario for exploration of the moon is that one or more astronauts would travel to a remote site in a pressurized or unpressurized ‘rover.’ An unpressurized rover trip would only last hours because the astronauts would be in spacesuits for the entire trek. A pressurized rover could sustain astronauts for a much longer trip, lasting days or weeks.

“If you are trying to conduct research with pressurized lunar vehicles, you run into many safety issues,” Cohen said. To avoid life-threatening or other compromising situations that might occur with only one rover traveling to a remote place, a second rover might travel with the first.

“But what if the second rover runs into a problem, too – the same or a different problem? Well, that means a third rover,” Cohen said. “So, why not make the entire base mobile, so that all the resources, reliability and redundancy of the lunar mission move with the excursion crew?” Cohen reasoned.

“In addition, there’s risk if you land lots of immobile modules in one spot — there is a danger you’ll have a very long commute to a place of scientific interest, or can’t get there. Then you’ve wasted billions of dollars. Mobile habitats greatly reduce the risk of finding yourself on the wrong place on the moon,” Cohen added.

Another advantage of mobile moon habitats is that they will be able to move out of the lunar landing zone, which could be hazardous. “The landing zone poses the problem that once a habitat lands on the moon, it is not prudent to land another vehicle within several kilometers because of safety concerns from ejecta in a normal landing, and in case of an explosive failure on impact,” Cohen said.

Cohen suggests that mobile habitats must have robust radiation shielding for them to be practical. “Radiation protection remains a challenge and a potential showstopper, as it does for all lunar base and rover concepts,” Cohen said. However, there are potential shielding concepts that may well be reasonable, according to Cohen.

The Office of Exploration Systems, NASA Headquarters, Washington, funds this research. Publication size images are available on the World Wide Web at:

Mobile Lunar Base

and

Mobile Lunar Base

More information about space architecture is on the Internet at:

http://www.spacearchitect.org

Original Source: NASA News Release

Posted on by Fraser Cain

Titan in Natural Colour

Despite the views of Titan?s surface that Cassini is able to provide, the moon remains inscrutable to the human eye. In true color images that are taken in the visible wavelengths, Titan?s photochemical smog, rich in organic material, gives the moon a smooth featureless orange glow.

The Cassini orbiter carries specially-designed spectral filters that can pierce Titan?s veil. Its piggybacked Huygens probe will descend through the atmosphere in early 2005, giving an up-close-and-personal look at this mysterious orange moon.

Images taken with the narrow angle camera using red, green and blue spectral filters were combined to create this color view. The images were obtained at a Sun-Titan-spacecraft, or phase, angle of 67 degrees and from a distance of approximately 13.1 million kilometers (8.2 million miles) on June 10, 2004. Image scale is approximately 79 kilometers (49 miles) per pixel.

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

Saturn’s Rotation is a Mystery

On approach to Saturn, data obtained by the Cassini spacecraft are already posing a puzzling question: How long is the day on Saturn?

Cassini took readings of the day-length indicator regarded as most reliable, the rhythm of natural radio signals from the planet. The results give 10 hours, 45 minutes, 45 seconds (plus or minus 36 seconds) as the length of time it takes Saturn to complete each rotation. Here’s the puzzle: That is about 6 minutes, or one percent, longer than the radio rotational period measured by the Voyager 1 and Voyager 2 spacecraft, which flew by Saturn in 1980 and 1981.

Cassini scientists are not questioning Voyager’s careful measurements. And they definitely do not think the whole planet of Saturn is actually rotating that much slower than it did two decades ago. Instead, they are looking for an explanation based on some variability in how the rotation deep inside Saturn drives the radio pulse.

The radio sounds of Saturn’s rotation, which are also the first sounds from Saturn studied by Cassini, are like a heartbeat and can be heard by visiting http://www.jpl.nasa.gov/videos/cassini/0604/ and http://www-pw.physics.uiowa.edu/space-audio

“The rotational modulation of radio emissions from distant astronomical objects has long been used to provide very accurate measurements of their rotation period,” said Dr. Don Gurnett, principal investigator for the Cassini Radio and Plasma Wave Science instrument, University of Iowa, Iowa City. “The technique is particularly useful for the giant gas planets, such as Jupiter and Saturn, which have no surfaces and are covered by clouds that make direct visual measurements impossible.”

The first hint of something strange about that type of measurement at Saturn was in 1997, when a researcher from Observatoire de Paris reported that Saturn’s radio rotation period differed substantially from Voyager.

Dr. Michael D. Desch, Cassini Radio Plasma Wave Science team member, and scientist at NASA?s Goddard Space Flight Center in Greenbelt, Md., has analyzed Saturn radio data collected by Cassini from April 29, 2003, to June 10, 2004. “We all agree that the radio rotation period of Saturn is longer today than it was in during the Voyager flyby in 1980,” he said.

Gurnett said, “Although Saturn’s radio rotation period has clearly shifted substantially since the Voyager measurements, I don?t think any of us could conceive of any process that would cause the rotation of the entire planet to actually slow down. So it appears that there is some kind of slippage between the deep interior of the planet and the magnetic field, which controls the charged particles responsible for the radio emission.” He suggests the solution may be tied to the fact that Saturn’s rotational axis is nearly identical to its magnetic axis. Jupiter, with a more substantial difference between its magnetic axis and its rotational axis, shows no comparable irregularities in its radio rotation period.

“This finding is very significant. It demonstrates that the idea of a rigidly rotating magnetic field is wrong,” said Dr. Alex Dessler, a senior research scientist at the University of Arizona, Tucson. In that way, the magnetic fields of gas giant planets may resemble that of the Sun. The Sun?s magnetic field does not rotate uniformly. Instead, its rotation period varies with latitude. “Saturn’s magnetic field has more in common with the Sun than the Earth. The measurement can be interpreted as showing that the part of Saturn?s magnetic field that controls the radio emissions has moved to a higher latitude during the last two decades,” said Dressler.

“I think we will be able to unravel the puzzle, but it’s going to take some time,” said Gurnett. ?With Cassini in orbit around Saturn for four years or more, we will be in an excellent position to monitor long-term variations in the radio period, as well as investigate the rotational period using other techniques.”

Cassini, carrying 12 scientific instruments, is just two days from its planetary rendezvous with Saturn. On June 30 it will become the first spacecraft to orbit Saturn, when it begins a four-year study of the planet, its rings and its 31 known moons. The spacecraft recently flew past Saturn?s cratered moon Phoebe, where it captured spectacular images as well as data on its mass and composition.

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. JPL designed, developed and assembled the Cassini orbiter.

For the latest images and more information about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini .

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Our Galactic Twin

What would our Milky Way galaxy look like if we could travel outside it and snap a picture? It might look a lot like a new image by NASA’s Spitzer Space Telescope of a spiral galaxy called NGC 7331 – a virtual twin of our Milky Way.

The picture, which can be viewed at http://photojournal.jpl.nasa.gov/catalog/PIA06322 , shows our twin as never before. Its swirling arms spin outward from a central bulge of light, which is outlined by a ring of actively forming stars.

“Being inside our galaxy makes it difficult to see what’s going on in the center,” said Dr. J.D. Smith, a member of the team that observed NGC 7331, and an astronomer at the University of Arizona, Tucson. “By looking at a very similar galaxy, we gain a bird’s eye-view of what the entire Milky Way might look like.”

Such an outside perspective will teach astronomers how our own galaxy, as well as others like it, might have formed and evolved.

The latest observations are the first in a large-scale effort to observe 75 nearby galaxies with Spitzer’s highly sensitive infrared eyes. Called Spitzer Infrared Nearby Galaxies Survey, the program will combine Spitzer data with that from other ground- and space-based telescopes operating at wavelengths ranging from ultraviolet to radio to create a comprehensive map of the selected galaxies.

The program’s first target, NGC 7331, was chosen in part for its striking similarities to the Milky Way. While these so-called twin galaxies do not share the same parents, they have many features in common, including number of stars, mass, spiral arm pattern and star-formation rate of a few stars per year. Whether the Milky Way has an inner star-forming ring like that of NGC 7331 is not known. NGC 7331 is located about 50 million light-years away in the constellation Pegasus.

The new Spitzer image demonstrates the power of the telescope’s infrared eyes to dissect galaxies into their various parts. Taken by the telescope’s infrared array camera, the false-colored picture readily distinguishes NGC 7331’s arms (brownish red), central bulge (blue) and star-forming ring (yellow). The composition of materials making up these regions was also revealed by the Spitzer observations: the central bulge consists primarily of older stars; the ring possesses a large amount of gas and dusty organic molecules called polycyclic aromatic hydrocarbons, which typically glow when illuminated by newborn stars; and the arms contain these same dust grains to a lesser degree. Polycyclic aromatic hydrocarbons are also found on Earth, on burnt toast and in car exhaust among other places.

Data from Spitzer’s infrared spectrograph instrument were also used to show that the center of NGC 7331 harbors either an unusually high concentration of massive stars, or a moderately active black hole about the same size as the one lurking at the core of our galaxy.

These findings will appear in two papers in the September issue of a special supplement to the Astrophysical Journal. Dr. Michael W. Regan of the Space Telescope Institute, Baltimore, Md., is lead author of a paper detailing observations from the infrared array camera, and Smith is lead author of a paper on the infrared spectrograph results. The Spitzer Infrared Nearby Galaxies Survey project is conducted by a team of about 25 scientists from 12 institutions, and is led by principal investigator Dr. Robert C. Kennicutt of the University of Arizona, Tucson.

Launched August 25, 2003, the Spitzer Space Telescope is the fourth of NASA’s Great Observatories, a program that also includes the Hubble Space Telescope, Chandra X-ray Observatory and Compton Gamma Ray Observatory.

JPL manages the Spitzer Space Telescope mission for NASA’s Office of Space Science, Washington, D.C. 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 spectrograph was built by Cornell University, Ithaca, N.Y., and Ball Aerospace Corporation, Boulder, Colo. The instrument’s development was led by Dr. Jim Houck of Cornell. Spitzer’s infrared array camera was built by NASA Goddard Space Flight Center, Greenbelt, Md. The camera’s development was led by Dr. Giovanni Fazio of Smithsonian Astrophysical Observatory, Cambridge, Mass.

Additional information about the Spitzer Space Telescope is available at http://www.spitzer.caltech.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Sea Launch Sends Telstar 18 Into Orbit

Sea Launch Company deployed Loral?s Telstar 18 communications satellite into orbit tonight from its ocean-based platform on the Equator. Early data indicate all systems aboard the spacecraft are in excellent condition.

The Sea Launch Zenit-3SL rocket lifted off at 8:59 pm PDT (3:59 GMT , June 29), as scheduled, from the Odyssey Launch Platform, positioned at 154 degrees West Longitude. On its way to a final orbital position at 138 degrees East Longitude, the spacecraft was separated into a reduced apogee orbit. A ground station in Perth, Australia, acquired the spacecraft?s first signal, shortly after spacecraft separation.

After the completion of the mission, Jim Maser, president and general manager of Sea Launch, said, ?We are still assessing the data and we are optimistic the spacecraft will achieve its specified lifespan on orbit. We are supporting our Loral customer in this assessment. We will issue additional information as it becomes available.?

Built by Space Systems/Loral and operated by Loral Skynet ? both subsidiaries of Loral Space & Communications ? the high-powered 1300-model spacecraft carries 54 active transponders, 16 Ku-band transponders and 38 C-band transponders. Once operational in the next few weeks, the Ku-band will reach China, India, Taiwan and Hong Kong, while the C-band capacity will cover Asia, Australia, New Zealand, the Pacific islands and Hawaii. The satellite will host cable programming, direct-to-home broadcasting, Internet, VSAT and IP-based two-way services within Asia while providing an inter-connect to the United States.

Sea Launch Company, LLC, headquartered in Long Beach, Calif., and marketed through Boeing Launch Services (www.boeing.com/launch), is the world?s most reliable commercial heavy-lift launch services provider. This multinational partnership offers the most direct and cost-effective route to geostationary orbit. With the advantage of a launch site on the Equator, the reliable Zenit-3SL rocket can lift a heavier spacecraft mass or provide longer life on orbit, offering best value plus schedule assurance. For additional information and images of this mission, please visit the Sea Launch website at: www.sea-launch.com

Original Source: Boeing News Release

Posted on by Fraser Cain

Air Leak Culprit Nearly Found

International Space Station (ISS) engineers are closing in on determining what caused a problem with Astronaut Mike Fincke’s Russian spacesuit. The malfunction stopped the Expedition 9 crew’s spacewalk just as it was getting started.

The primary oxygen bottle on Fincke’s Orlan suit began losing pressure faster than expected. Fincke was not in danger, but the crew was directed to return to the airlock, close the hatch and end the spacewalk after about 14 minutes.

The earliest the spacewalk could be rescheduled is Tuesday, June 29 based on Russian ground communications coverage.

During evaluations today, Russian specialists had the crew focus on an injector switch that increases the flow of oxygen into the spacesuit. The crew was asked to manipulate the switch on-and-off several times. Also discussed was the status of an indicator light on the suit for the injector system.

The Russian flight control team assured Expedition 9 Commander Gennady Padalka and Fincke, they believe the crew executed the spacewalk procedures well and didn’t do anything that would have caused the decrease in pressure. The crew was also told to expect to use the same suits when the spacewalk is rescheduled.

Investigations into the cause of the decrease in oxygen tank pressure will continue throughout the weekend. The ISS Mission Management Team will discuss the progress of analysis and plans Tuesday morning. The goal of the spacewalk is to replace a faulty circuit breaker on the exterior of the ISS to restore power to a gyroscope that helps control the Station’s orientation in orbit.

Yesterday, Fincke and Padalka opened the Pirs docking compartment hatch at 5:56 p.m. EDT. Immediately after Fincke floated out of the airlock, flight controllers in Moscow saw readings that indicated Fincke’s suit was losing oxygen pressure.

The spacewalkers returned to the airlock and closed the hatch. After conducting preliminary troubleshooting activities, Padalka and Fincke were asked to remove the Orlan spacesuits and assist with troubleshooting of Fincke’s suit. The duration of the spacewalk was 14 minutes, 22 seconds.

Fincke told Mission Control in Houston, he was pleased flight controllers in Moscow had discovered the oxygen tank problem so quickly and thanked both control teams for their efforts.

The ISS has four Control Moment Gyroscopes (CMGs) that are designed to control which way the Station is pointed as it orbits the Earth. CMG 1 failed about two years ago and will be replaced during the next Space Shuttle mission. CMG 2 was taken off line April 21 when a circuit breaker failed. Power to CMG 2 should be restored after the spacewalk. Meanwhile, the two other CMGs are adequately controlling the Station’s orientation.

Original Source: NASA News Release

Posted on by Fraser Cain

This Star Just Shut Down

An international team of astronomers, studying the left-over remnants of stars like our own Sun, have found a remarkable object where the nuclear reactor that once powered it has only just shut down. This star, the hottest known white dwarf, H1504+65, seems to have been stripped of its entire outer regions during its death throes leaving behind the core that formed its power plant.

Scientists from the United Kingdom, Germany and the USA focused two of NASA’s space telescopes, the Chandra X-ray observatory and the Far Ultraviolet Spectroscopic Explorer (FUSE), onto H1504+65 to probe its composition and measure its temperature. The data revealed that the stellar surface is extremely hot, 200,000 degrees, and is virtually free of hydrogen and helium, something never before observed in any star. Instead, the surface is composed mainly of carbon and oxygen, the ‘ashes’ of the fusion of helium in a nuclear reactor. An important question we must answer is why has this unique star lost the hydrogen and helium, which usually hide thestellar interior from our view?

Professor Martin Barstow (University of Leicester) said. ‘Studying the nature of the ashes of dead stars give us important clues as to how stars like the Sun live their lives and eventually die. The nuclear waste of carbon and oxygen produced in the process are essential elements for life and are eventually recycled into interstellar space to form new stars, planets and, possibly, living beings.’

Professor Klaus Werner (University of TUbingen) said. ‘We realized that this star has, on astronomical time scales, only very recently shut down nuclear fusion (about a hundred years ago). We clearly see the bare, now extinct reactor that once powered a bright giant star.’

Dr Jeffrey Kruk (Johns Hopkins University) said: ‘Astronomers have long predicted that many stars would have carbon-oxygen cores near the end of their lives, but I never expected we would actually be able to see one. This is a wonderful opportunity to improve our understanding of the life-cycle of stars.’

The Chandra X-ray data also reveal the signatures of neon, an expected by-product of helium fusion. However, a big surprise was the presence of magnesium in similar quantities. This result may provide a key to the unique composition of H1504+65 and validate theoretical predictions that, if massive enough, some stars can extend their lives by tapping yet another energy source: the fusion of carbon into magnesium. However, as magnesium can also be produced by helium fusion, proof of the theory is not yet ironclad. The final link in the puzzle would be the detection of sodium, which will require data from yet another observatory: the Hubble Space Telescope. The team has already been awarded time on the Hubble Space Telescope to search for sodium in H1504+65 next year, and will, hopefully, discover the final answer as to the origin of this unique star.

Original Source: RAS News Release

Posted on by Fraser Cain

Cassini’s Best View of Titan Yet

The Cassini spacecraft has beamed back a new, more detailed image of smog-enshrouded Titan.

This view represents an improvement in resolution of nearly a factor of three over the previous Cassini image release about Titan. The observed brightness variations are real on scales of a hundred kilometers or less.

The image was obtained in the near-infrared (centered at 938 nanometers) through a polarizing filter. The combination was designed to reduce the obscuration by atmospheric haze. The haze is more transparant at 938 nm than it is at shorter wavelengths and light of 938 nm wavelength is not absorbed by methane gas in Titan’s atmosphere. Light at this wavelength consequently samples the surface, and the polarizer blocks out light scattered mainly by the haze. This is similar to the way a polarizer, put on the front of a lens of a hand-held camera, makes distant objects more clear on the Earth.

The superimposed coordinate system grid in the accompanying image at right illustrates the geographical regions of the moon that are illuminated and visible, as well as the orientation of Titan ? north is up and rotated 25 degrees to the left. The yellow curve marks the position of the boundary between day and night on Titan.

This image shows about one quarter of Titan’s surface, from 0 to 70 degrees West longitude, and just barely overlaps part of the surface shown in the previous Titan image release. Most of the visible surface in this image has not yet been shown in any Cassini image release.

The image was obtained with the narrow angle camera on June 14, 2004, at a phase, or Sun-Titan-spacecraft, angle of 61 degrees and at a distance of 10.4 million kilometers (6.5 million miles) from Titan. The image scale is 62 kilometers (39 miles) per pixel. The image was magnified by a factor of two using a linear interpolation scheme. No further processing to remove the effects of the overlying atmosphere has been performed.

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.